Animal Vaccination Part 2_scientific, Economic, Regulatory and Socio-ethical Aspects

ORGANISATION MONDIALE DE LA SANTÉ ANIMALEWORLD ORGANISATION FOR ANIMAL HEALTHORGANIZACIÓN MUNDIAL DE SANIDAD ANIMAL

R E V U ESCIENTIFIQUE ET TECHNIQUE

SCIENTIFIC AND TECHNICAL

R E V I E WR E V I S T ACIENTÍFICA Y TÉCNICA

Animal vaccinationPart 2: scientific, economic, regulatory and socio-ethical aspects

Vaccination animalePartie 2 : aspects scientifiques,économiques, réglementaires et socio-éthiques

Vacunación animalParte 2: aspectos científicos, económicos, reglamentarios y socio-éticos

Co-ordinated byCoordonné par P.-P. Pastoret, M. Lombard & A.A. SchudelCoordinado por

VOL. 26 (2)AUGUST – AOÛT– AGOSTO2007

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© Office international des épizooties, 2007

ISSN 0253-1933ISBN 978-92-9044-687-3Vol. (1) ISBN 978-92-9044-688-0Vol. (2) ISBN 978-92-9044-689-7

Le papier choisi pour l’impression de cet ouvrage, étant recyclé à 50 % et exempt à 100 % de chlore et d’acide, ne peut pas nuire àl’environnementThis book is printed on 50% recycled, 100% chlorine and acid-free environmentally friendly paperEl papel escogido para la impresión de este libro está reciclado al 50% y no contiene cloro ni ácidos, por lo que no puede causarperjuicio al medio ambiente

Conception maquette / Graphic design / Diseño de la maqueta: J. Prieur – Tous les cheminsConception couverture/ Cover design / Diseño de cubierta: P. Blandin, OIEImages de la couverture / Images of the cover / Imágenes de la cubierta: © A. Thiermann, © P.-P. Pastoret

Contents – Sommaire – ContenidoAnimal vaccination Part 2: scientific, economic, regulatory and socio-ethical aspectsVaccination animale Partie 2 : aspects scientifiques, économiques, réglementaires et socio-éthiquesVacunación animalParte 2: aspectos científicos, económicos, reglamentarios y socio-éticos

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307Préface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308Prólogo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

A. McLeod & J. RushtonEconomics of animal vaccination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313Économie de la vaccination animale (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323Aspectos económicos de la vacunación animal (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

K.A. Schat & E. BaranowskiAnimal vaccination and the evolution of viral pathogens . . . . . . . . . . . . . . . . . . . . . . . . 327La vaccination des animaux et l’évolution des virus (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334Vacunación de animales y evolución de los patógenos virales (resumen) . . . . . . . . . . . . . . . . . . . . 335

K. Grein, O. Papadopoulos & M. TollisSafe use of vaccines and vaccine compliance with food safety requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339Utilisation sans risques de la vaccination et conformité des vaccins avec les exigences de la sécurité sanitaire des aliments (résumé) . . . . . . . . . . . . . . 348Utilización segura de vacunas y observancia de las normas sobre higiene de los alimentos en el uso de vacunas (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

P. Vannier, I. Capua, M.F. Le Potier, D.K.J. Mackay, B. Muylkens, S. Parida, D.J. Paton & E. Thiry

Marker vaccines and the impact of their use on diagnosis and prophylactic measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351Les vaccins à marqueurs et les conséquences de leur utilisation sur le diagnostic et la prophylaxie (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363Vacunas marcadoras y sus consecuencias sobre el diagnóstico y medidas de profilaxis (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

Rev. sci. tech. Off. int. Epiz., 26 (2), 2007

The scientific and economic basis of vaccination – Les fondements scientifiques et économiques de la vaccination – Las bases científicas y económicas de la vacunación

S. Edwards

OIE standards for vaccines and future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

Normes de l’OIE relatives aux vaccins et tendances pour l’avenir (résumé) . . . . . . . . . . . . . . . . . . 377

Normas de la OIE sobre vacunas y tendencias de cara al futuro (resumen) . . . . . . . . . . . . . . . . . . 377

P.G.H. Jones, G. Cowan, M. Gravendyck, T. Nagata, S. Robinson & M. WaitsRegulatory requirements for vaccine authorisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379Exigences réglementaires liées à l’agrément des vaccins (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . 392Requisitos de las reglamentaciones relativas a la autorización de comercialización de vacunas (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392

C. Saegerman, M. Hubaux, B. Urbain, L. Lengelé & D. BerkvensRegulatory issues surrounding the temporary authorisation of animal vaccination in emergency situations: the example of bluetongue in Europe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395Questions réglementaires liées à l’autorisation temporaire de vacciner les animaux en situation d’urgence : l’exemple de la fièvre catarrhale du mouton en Europe (résumé) . . . 406Cuestiones de reglamentación en torno a la autorización temporal de vacunación de animales en situaciones de emergencia: el ejemplo de la lengua azul en Europa (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407

M. Holmes & R.E. Hill International harmonisation of regulatory requirements . . . . . . . . . . . . . . . . . . . . . . . . . 415Harmonisation internationale des dispositions réglementaires (résumé) . . . . . . . . . . . . . . . . . . . . . 419Armonización internacional de los requisitos reglamentarios (resumen) . . . . . . . . . . . . . . . . . . . . . 420

D.K.J. MackayAuthorisation within the European Union of vaccines against antigenicallyvariable viruses responsible for major epizootic diseases . . . . . . . . . . . . . . . . . . . . . . . 421L’agrément au sein de l’Union européenne des vaccins dirigés contre des virus épizootiques majeurs présentant une variabilité antigénique (résumé) . . . . . . . . . . . . . . . . . . . . . . . 426Autorización de vacunas contra los virus con variaciones antigénicas responsables de las principales enfermedades epizoóticas en la Unión Europea (resumen) . . . . . . . . . . . . . . . . 426

L.A. Elsken, M.Y. Carr, T.S. Frana, D.A. Brake, T. Garland, K. Smith & P.L. FoleyRegulations for vaccines against emerging infections and agrobioterrorism in the United States of America . . . . . . . . . . . . . . . . . . . . . . . . . . . 429Réglements applicables aux vaccins contre les maladies infectieuses émergentes et à l’agrobioterrorisme aux États-Unis d’Amérique (résumé) . . . . . . . . . . . . . . . . . . . 440Reglamentación sobre vacunas contra infecciones emergentes y bioterrorismo en los Estados Unidos de América (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

Rev. sci. tech. Off. int. Epiz., 26 (2)300

Regulatory aspects – Aspects réglementaires – Aspectos reglamentarios

J.-Ch. Audonnet, J. Lechenet & B. VerschuereL’expérimentation animale dans la découverte et la production de vaccins à usage vétérinaire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443Animal experimentation in the discovery and production of veterinary vaccines (summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448La experimentación con animales en relación con el descubrimiento y la producción de vacunas de uso veterinario (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448

J.M. ScudamoreConsumer attitudes to vaccination of food-producing animals . . . . . . . . . . . . . . . . . 451Comportement des consommateurs à l’égard de la vaccination des animaux destinés à l’alimentation humaine (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457Actitud del consumidor frente a la vacunación de animales destinados al consumo humano (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

C.M. Hardy & A.L. BraidVaccines for immunological control of fertility in animals . . . . . . . . . . . . . . . . . . . . . . . 461Les vaccins et le contrôle immunologique de la fécondité chez les animaux (résumé) . . . . . . . 466Vacunas para el control inmunológico de la fertilidad en animales (resumen) . . . . . . . . . . . . . . . 466

D. O’Brien & S. ZankerAnimal vaccination and the veterinary pharmaceutical industry . . . . . . . . . . . . . . . 471La vaccination animale et l’industrie pharmaceutique vétérinaire (résumé) . . . . . . . . . . . . . . . . . . 476Vacunación animal e industria farmacéutica veterinaria (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . 477

L. Miguens Opinión del sector ganadero sobre el rol de las vacunas en el control y erradicación de las enfermedades del ganado en Argentina . . . . 479Le point de vue des éleveurs argentins sur le rôle de la vaccination dans le contrôle et l’éradication des maladies du bétail (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483The opinion of the production sector on the role of vaccinesin the control and eradication of livestock diseases in Argentina . . . . . . . . . . . . . 485

P.-P. Pastoret, A.A. Schudel & M. LombardConclusions – Future trends in veterinary vaccinology . . . . . . . . . . . . . . . . . . . . . . . 489-494Conclusions – Tendances futures de la vaccinologie vétérinaire . . . . . . . . . . 495-501Conclusiones – Tendencias futuras del estudio de vacunas veterinarias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503-509

Rev. sci. tech. Off. int. Epiz., 26 (2) 301

Socio-ethical aspects – Aspects socio-éthiques – Aspectos socio-éticos


E. Thiry & M.C. HorzinekVaccination guidelines: a bridge between official requirements and the daily use of vaccines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511Les lignes directrices de la vaccination : un pont entre les besoins officiels et l’utilisation quotidienne des vaccins (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516Las directrices de vacunación como nexo entre los requisitos oficiales y el uso cotidiano de las vacunas (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516

A.A. Schudel & M. LombardRecommendations of the OIE International Conference on the Control of Infectious Animal Diseases by Vaccination, Buenos Aires, Argentina, 13 to 16 April 2004 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519

A.A. SchudelVaccines and OIE listed diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523

Appendices – Annexes – Anexos


Animal vaccination. Part 1: development, production and use of vaccines. Vol. 26 (1)Vaccination animale. Partie 1 : développement, production et utilisation des vaccins. Vol. 26 (1)Vacunación animal. Parte 1: desarrollo, producción y utilización de vacunas. Vol. 26 (1)

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Préface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Prólogo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

P.-P. Pastoret, M. Lombard, A.A. Schudel, J. Plana-Durán & A. WennbergIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Introducción . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

M. Lombard, P.-P. Pastoret & A.-M. MoulinA brief history of vaccines and vaccination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Une brève histoire des vaccins et de la vaccination (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Una breve historia de las vacunas y la vacunación (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

C.G. Gay, R. Zuerner, J.P. Bannantine, H.S. Lillehoj, J.J. Zhu, R. Green & P.-P. Pastoret

Genomics and vaccine development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49La génomique et la mise au point de vaccins (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Genómica y desarrollo de vacunas (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

J.A. MumfordVaccines and viral antigenic diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Les vaccins et la variabilité antigénique des virus (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Vacunas y variabilidad antigénica de los virus (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

M. Gottschalk & S. Laurent-LewandowskiLes vaccins face à la diversité antigénique des bactéries . . . . . . . . . . . . . . . . . . . . . . . 91Vaccine development: strategies for coping with the antigenic diversity of bacteria (summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Las vacunas ante la diversidad antigénica de las bacterias (resumen) . . . . . . . . . . . . . . . . . . . . . . . 99

Development and production of vaccines – Développement et production des vaccins –Desarrollo y producción de vacunas


J. Vercruysse, T.P.M. Schetters, D.P. Knox, P. Willadsen & E. ClaereboutControl of parasitic disease using vaccines: an answer to drug resistance? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105Prophylaxie des maladies parasitaires au moyen de la vaccination : une réponse à la résistance aux médicaments ? (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111El control de enfermedades parasitarias por las vacunas como posible solución al problema de la farmacorresistencia (resumen) . . . . . . . . . . . . . . . . . . . . 112

M. Lombard & A.-E. Füssel

Antigen and vaccine banks: technical requirements and the role of the European antigen bank in emergency foot and mouth disease vaccination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Banques d’antigène et de vaccins : prescriptions techniques,

et rôle de la banque d’antigène de l’Union européenne dans la vaccination

d’urgence contre la fièvre aphteuse (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

Bancos de antígenos y vacunas: requisitos técnicos y papel

del banco europeo de antígenos en vacunaciones de emergencia

contra la fiebre aftosa (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

J.I. ToddGood manufacturing practice for immunological veterinary medicinal products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135Bonnes pratiques de fabrication pour les médicaments vétérinaires immunologiques (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143Buenas prácticas de fabricación de productos inmunológicos veterinarios (resumen) . . . . . . . . 144

G. Mutwiri, V. Gerdts, M. Lopez & L.A. BabiukInnate immunity and new adjuvants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147L’immunité innée et les nouveaux adjuvants (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153Inmunidad innata y nuevos adyuvantes (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

D.B. MortonVaccines and animal welfare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157Les vaccins et le bien-être des animaux (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161Vacunas y bienestar animal (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

D. Lütticken, R.P.A.M. Segers & N. VisserVeterinary vaccines for public health and prevention of viral and bacterial zoonotic diseases . . . . . . . . . . . . . . . . . . . . . . . . . 165Les vaccins vétérinaires en santé publique et la prévention des zoonoses virales et bactériennes (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173Vacunas veterinarias para la salud pública y prevención de enfermedades zoonóticas virales y bacterianas (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

Why use vaccines? – Pourquoi utiliser des vaccins ? – ¿Por qué utilizar vacunas?


J. Lubroth, M.M. Rweyemamu, G. Viljoen, A. Diallo, B. Dungu & W. AmanfuVeterinary vaccines and their use in developing countries . . . . . . . . . . . . . . . . . . . . . . 179Les vaccins vétérinaires et leur utilisation dans les pays en développement (résumé) . . . . . . . 196Las vacunas veterinarias y su utilización en los países en desarrollo (resumen) . . . . . . . . . . . . . 197

N. Marano, C. Rupprecht & R. RegneryVaccines for emerging infections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203Les vaccins contre les maladies infectieuses émergentes (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . 210Vacunas contra infecciones emergentes (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

I. CapuaVaccination for notifiable avian influenza in poultry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217La vaccination des volailles contre l’influenza aviaire à déclaration obligatoire (résumé) . . . . 224Vacunación de aves de corral contra la influenza aviar de notificación obligatoria (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

G. Plumb, L. Babiuk, J. Mazet, S. Olsen, P.-P. Pastoret, C. Rupprecht & D. SlateVaccination in conservation medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229La vaccination et la médecine environnementale (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236La vacunación en medicina de la conservación (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

T. Wisniewski, J.A. Chabalgoity & F. GoniIs vaccination against transmissible spongiform encephalopathy feasible? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243La vaccination contre l’encéphalopathie spongiforme transmissible est-elle une option réaliste ? (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247¿Es factible la vacunación contra la encefalopatía espongiforme transmisible? (resumen) . . 248

P.L. Roeder & W.P. TaylorMass vaccination and herd immunity: cattle and buffalo . . . . . . . . . . . . . . . . . . . . . . . . 253La vaccination de masse et l’immunité de troupeau : bovins et buffles (résumé) . . . . . . . . . . . . . 260Vacunación masiva e inmunización de los rebaños de vacunos y búfalos (resumen) . . . . . . . . . 261

S. Marangon & L. BusaniThe use of vaccination in poultry production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265La vaccination dans les élevages de volailles (résumé) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272Vacunación en establecimientos avícolas (resumen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

Rev. sci. tech. Off. int. Epiz., 2007, 26 (2), 313-326

Economics of animal vaccinationA. McLeod & J. Rushton

Livestock Information, Sector Analysis and Policy Branch, Animal Production and Health Division, Food andAgriculture Organization (FAO)The views presented in this paper are the authors’ own and do not constitute an official statement from FAO.

SummaryThis paper describes the steps that might be used in assessing the economicjustification for using vaccination to control animal disease, and the way thatvaccination is financed and administered. It describes decisions that have beentaken with respect to preserving international trade, and issues related toprotection of livelihoods. Regardless of the motivation for vaccination, its costscan usually be shared between the public and private sectors. Cost-effectivevaccination requires methods of delivery to be adapted to livestock productionsystems. The paper concludes by suggesting questions around the use ofvaccination that would merit further economic analysis.

KeywordsAnimal disease – Economics – Livelihood – Vaccination

IntroductionThe paper addresses two subject areas, namely: theeconomic justification for using, or not using, vaccinationin disease control; and the way that it is financed andadministered. Interested parties may include the following:

– governments deciding whether to permit or forbid theuse of vaccination, or make it compulsory

– farmers deciding whether or not to pay for vaccine fortheir herds and flocks, and whether to comply withrequirements to present their animals for vaccination

– those who produce and supply vaccine

– those concerned with the welfare of farmers and theiranimals.

Most readers will be familiar with the basic principles bothof vaccination and of the economic analysis of animalhealth. The former are covered in this issue of the WorldOrganisation for Animal Health (OIE) Scientific andTechnical Review. Aspects of economic analysis andmodelling of animal health have been dealt with in varyingdegrees of complexity by many authors (18, 30, 33, 37, 42,

45, 48). General thinking on animal health and livestockeconomics, including new institutional economics, hasalso been variously described by many authors (1, 12, 16,26, 28, 40, 48, 49). A summary of economic methods foranimal health was made recently by Rich et al. (32).

Rather than repeating what has been well described, thispaper concentrates on the practicality of applyingeconomic analysis to assessment of vaccination, byidentifying a series of key questions and reviewing the wayin which decisions have actually been made in differentsituations. A stepwise process is used to lay out the mostimportant issues, although in reality, decisions are seldomas linear or clear cut as they are in conceptual models. Theprocess is as follows:

a) The first step is to assess whether vaccination istechnically viable; that is, whether a vaccine exists and canbe applied safely and effectively.

b) Assuming that vaccination is technically possible, twoeconomic questions may underpin the decision to apply it,allow it or forbid it, they are:

– whether the use of vaccination will adversely affectinternational trade in livestock products

– whether the use of vaccination could protectlivelihoods, particularly those of vulnerable people, orotherwise reduce distress.

It is not impossible that conflicting answers will arise, andin this case, it is necessary to weigh objectives and make achoice, or to look for an acceptable compromise.

c) The next factors to be considered are the institutionaland operational conditions that affect the assumptionsunderlying economic analysis. Here, two closely relatedpoints must be examined:

– the funding source for vaccination, which may be publicor private or a mixture of both

– regardless of the source of funding, the delivery ofvaccination should be cost effective. This means that thedelivery process needs to be adapted to the productionsystems in which vaccination is applied, and the potentialrecurrent costs of vaccination should be examinedcarefully before a programme is started.

The remainder of the paper examines each of the abovepoints in turn, and then concludes by identifying areaswhere animal health planners would benefit from furthersupport or new economic analyses to assist in decisionsabout the use of vaccination in animal disease control.

Technical viability of vaccinationVaccination may be considered for the following purposes:

– to stamp out an outbreak in a country, zone (ageographically continuous area separated from infectedareas by a surrounding buffer zone) or compartment (acomponent of a management system under a commonbiosecurity regime, e.g. the biosecure production,slaughter and processing units of an industrial value chain,with animals and feed moved between units in biosecuretransportation) that has previously been free of disease orfree of virus

– to eradicate disease (when it is used in the early stagesof a programme to reduce virus load)

– to establish and then protect a disease-free zone

– to achieve a low level of incidence of clinical disease inareas where it is endemic.

In the first case, that of stamping out a new outbreak,vaccination together with reduced culling may beconsidered as an alternative to widespread culling.Vaccinating in a ring around an outbreak and culling in asmaller inner ring reduces the number of animals that need

to be slaughtered in the immediate outbreak controlaction. For this strategy to work, necessary conditionswould include the existence of a safe and effective vaccine,and rapid onset of protection at individual level.Vaccination has been used in stamping out of foot andmouth disease (FMD) outbreaks, for example in theNetherlands, when insufficient personnel and equipmentwere available for culling. At the time of writing, ringvaccination was being reviewed by several countries for thecontrol of highly pathogenic avian influenza (HPAI) sincevaccines have been developed that provide good protectionto poultry. The main technical concerns were thatvaccinated birds must not increase the risk to humans,since they greatly reduce clinical disease but do notcompletely eliminate virus shed, and that birds could beadequately protected against spread in the poultrypopulation when full protection was only conferred aftertwo applications of vaccine. There is always a concernwhen using vaccination in an emergency situation that asufficient amount of vaccine can be provided at shortnotice, since vaccine has a finite shelf life andmanufacturers cannot afford to maintain large stocksagainst uncertain future orders.

Vaccination has been an important component ineradication programmes, including those involvingprogressive zoning, such as those for rinderpest in Africaand FMD in Latin America. The technical challenge inusing vaccination for eradication is to obtain on aconsistent basis sufficiently high levels of herd immunity toprevent virus spread (the protection level needed dependson the reproductive rate of the virus. It can be as high as80% or considerably lower, depending on the ease oftransmission and the opportunities for animals to comeinto contact), often under difficult field conditions.Rinderpest devastated African cattle herds in the 19thCentury and had become very widespread in less virulentforms in the 20th Century. An effective vaccine wasproduced several years ago that confers lifelong immunity,and later, a thermostable form was developed that could bedelivered without a cold chain. It was therefore possible,with annual vaccination programmes, to maintain a level ofimmunity in the herd sufficient to drive back disease. Inmany countries disease has reduced to a point wherevaccination could be stopped and the few remainingoutbreaks controlled with surveillance and stamping out.Vaccination against FMD, although it has been usedsuccessfully in control programmes, is less straightforwardbecause the vaccines available against FMD offer only ashort span of protection, and bi- or tri-valent vaccines areneeded to protect against the many and changing virus strains.

When vaccination is used as a preventive measure to keepincidence below certain levels, a vaccine is needed that canbe applied effectively (by farmers as well as veterinarians).It is applied in this way to deal with classical swine fever


(CSF) in parts of Asia and brucellosis in many countries. Itis also used against Newcastle disease (ND) and rabies,where there may be reservoirs of infection in wild animals.ND occurs all over the world and sweeps throughsmallholder poultry flocks from time to time, causing highmortality. Well-tested vaccines exist that can be used as apreventive measure in less than optimal field conditions,and applied even without injection, and they offer themeans for individual farmers to protect their flocks.

For some important diseases, such as African swine fever(ASF) and bovine spongiform encephalopathy (BSE)vaccines do not exist and the only possibilities for theircontrol are good hygiene management to improvebiosecurity of herds or stamping out measures (culling anddisinfection together with movement control) to removeoutbreaks. Even where good vaccines do exist, vaccinationprogrammes must always be supported by surveillance andbacked up by other measures.

When the basic technical requirements for usingvaccination have been met, it can be examined foreconomic viability. Two important considerations facingdecision makers are the use of vaccination in countriesengaged in international trade, and the possible benefits ofvaccination in protecting livelihoods, particularly those of vulnerable people. Each of these will now be examinedin turn.

Vaccination and international tradeFigure 1 reminds us of the well recognised trend towardsincreasing international trade in livestock commodities,particularly from developing countries. In 1990developing countries accounted for 30% of internationaltrade while by the end of 2006 the figure was expected to

reach 47% (23, based on Food and AgricultureOrganization [FAO] data). Developing and emergingeconomies, whose resource base allows them to becompetitive, have increasing importance in production, inparticular the ‘big three’, Brazil, China and India (39). Inmany countries with strong livestock production growth,there continue to be problems with animal disease control.There has been a shift towards processed products amongthe industrial producers, in large part because of increasedconcerns about animal health and food safety regulations.

The ability to export livestock and their products dependson equivalence of animal health and food safetyconditions, particularly with regard to animal diseases thathave been defined as notifiable by the OIE (50). Currently,countries where notifiable diseases are present have limitedpotential to export unprocessed livestock products or liveanimals to those that can prove they do not have the samediseases, although it is possible to export processedproducts such as heat-treated or de-boned meat. Forexporting countries wishing to access premium markets,freedom from notifiable diseases forms a majorpreoccupation for their Veterinary Services and thecommercial livestock sector.

Increasingly it is being recognised and defined ininternational guidelines that disease freedom may applynot only to a country but also to a zone or a compartment.While the concept of a zone is quite well accepted, that ofthe compartment is less so. Thailand has been exploringthe possibility of defining disease-free and vaccination-freecompartments for export of poultry (22) which mightallow targeted vaccination in smallholder flocks outside thecompartments. It has been difficult to arrive at a technicallyand financially viable design that is acceptable toimporters. The concept of safe commodity trading alsoallows for some flexibility. Essentially, it argues that acertified processed product such as de-boned beef from ahazard analysis critical control point (HACCP)-accreditedslaughterhouse should be exportable even if vaccination isbeing applied in other parts of the livestock sector. This hasalways been possible to some extent, since processedproducts are exported from countries that vaccinate againstcertain diseases. It is of great interest in the Horn of Africa,where ruminant meat from extensive systems is the mainexportable product. Gradient systems (those that allowdifferent conditions for different parts of the livestocksector) have many attractions. There are, however,concerns that flexible standards in animal health and foodsafety might actually mean double standards, withpremium markets getting better care and attention whileothers are offered a second-class product. One way toprevent that happening is to pay attention to providingsuitable services to all types of production system.

Importing countries free of disease and not vaccinatingmay decline to take animal products from countries, or


Fig. 1Growth in world meat exportsSource: Morgan, 2006 (23)

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zones, that vaccinate, and will try to control rare outbreaksby culling, disinfection and movement control rather thanvaccination. A country trying to achieve official recognitionof disease freedom can only do so after a progressivecontrol programme and months or years free of anyoutbreak (the OIE regulations define precise periods forsome diseases, for others it is a matter of negotiationbetween trading partners). Disease freedom whenvaccination is applied, even if it can reliably bedemonstrated that there is no clinical disease, is neverconsidered equivalent to freedom without vaccination byimporting countries that are free without vaccination (e.g.FMD vaccination can be used for a short time to control anoutbreak in a previously free area, but it must quickly bewithdrawn and the area monitored for some time beforetrade can recommence), even if the OIE Terrestrial AnimalHealth Code may not differentiate the requirement. Thebenefits of achieving and maintaining a premium exportmarket can be considerable. Uruguay spent between US$7 million and US$9 million a year on FMD vaccinationprior to 1997. Once it was declared free of FMD, it gainedaccess to a beef market in the United States of America(USA) worth around US$20 million a year above the valueof previous domestic sales (17).

When a country trades in livestock products on the basisof freedom from certain diseases without vaccination, thecritical economic question will be: in the event of a diseaseoutbreak, should vaccination be used to control it? WhenBotswana experienced a contagious bovinepleuropneumonia (CBPP) outbreak in the 1990s, thedecision was made to use slaughter and compensationrather than vaccination for control, in order to re-establishits export market to the European Union (EU) morequickly, although a programme based on vaccination costonly 78% of one based on culling and compensation (19).Thailand was one of the first countries to report HPAIwhen a series of outbreaks began in Asia in 2003. By March2004, the cost of compensation alone had been US$46.5 million, paid to 407,338 farmers. With disease in51 provinces and a silently infected duck population in thewetland areas, it would have been a reasonable decision tomove to widespread vaccination. However, Thailand’spoultry meat export industry was valued at US$597,634,000 in 2003 (it held fifth place in theglobal export market, falling to 17th in 2004 [6]), so thedecision was made to try to eradicate disease withoutvaccination. A house-to-house ‘x-ray’ survey wasimplemented to seek out disease, and all subsequent caseswere rapidly investigated, reported and stamped out.These efforts greatly reduced disease but have not yeteliminated it, and recovery of the export trade wasachieved largely by expanding processed products.

Countries in trading blocs try to create harmonious rulesabout animal health, so that countries within the bloc cantrade with each other under reduced transactions costs.

The countries of the EU try to remain free of notifiableanimal diseases without vaccination, and when a memberof the bloc experiences an outbreak there is peer pressureto control it by stamping out measures. In the UnitedKingdom (UK), an outbreak of FMD in 2001 wascontrolled without the use of vaccination, although atconsiderable cost in terms of lost animals. There were nomajor markets threatened at that time, as beef marketswere closed due to BSE, the predominant lamb marketswere for low value product to Spain and Italy and porkmarkets were for cuts that did not sell in the UK, but therewas a strong political will to eradicate the disease. This waseventually achieved, but not without the loss ofconsiderable numbers of animals, losses in other ruralindustries, psychological effects on farmers and concernsamong the general public about slaughter of healthyanimals (36). Risk modelling carried out after the outbreaksuggests that vaccination with reduced culling mightreduce the numbers of animals culled on disease groundsby 15% to 50%, although culling on welfare grounds might increase slightly (welfare culling may bepermitted when animals are kept beyond their normalselling age and farmers cannot afford to feed them) (34). In2001, the European Commission (EC) and OIE guidelineson the use of vaccination were very inflexible. Since 2001,the EC has revised its directives on FMD control to providegreater flexibility in the use of vaccination. At the sametime, the OIE has agreed a reduction in the use of the‘holding period’ before freedom from disease can bedeclared. The development of differentiating infected fromvaccinated animals (DIVA) strategies – making it possibleto distinguish in serological tests between antibodies fromdisease and those from vaccination – offers furtherpotential for limited use of vaccination by exportingcountries. However, there has not yet been a re-examination of the UK data to assess whether vaccinationwould be economically and technically viable undercurrent regulatory conditions.

For countries engaged in international trade of live animalsor unprocessed products, therefore, there will be hesitationin permitting vaccination to be used in disease control. In the event of an outbreak, a stamping out process thatrelies on culling and movement control rather thanvaccination will promote a faster return to trade, providedthat it is successful.

Protecting livelihoods and human well-beingAnimal vaccination may have a role to play in protectingthe livelihoods of producers and traders of livestock, andindividuals employed in the livestock sector, particularlysmall-scale operators whose livelihoods are vulnerable


because they have limited safety nets. Vaccination is likelyto be beneficial to livelihoods in the following situations:

– when it can be used to control disease effectively withminimal depopulation, particularly in situations whereadequate compensation for culled animals is not available

– when it prevents the disruption of national markets orallows markets to be restored quickly, thereby protectingthe livelihoods of those who sell into the markets, and theproviders of services, and those employed in the livestocksector

– as an ‘insurance’ against disease losses by privatefarmers or an investment in protection of an industry

– when it minimises the disruption of other sectors linkedto livestock, such as leisure and tourism.

When stamping out measures are used to deal with anemerging or re-emerging disease, the effect on the nationaleconomy of the culling of even quite large numbers ofanimals may be minimal. Unfortunately, the effect on thelivelihoods of those immediately affected may be severe.Depopulation of animals other than occasionally and on avery small scale can be badly damaging to livelihoods ofsmallholders and small-scale traders who rely on regular orinstantly accessible cash flow from their livestock. Wherethe animals are owned or managed by women, as is oftenthe case with smaller species, income from them tends tobe used directly for buying food, and loss of this incomehas an adverse effect on household food security (7). Insmall herds and flocks, a certain level of risk is acceptedand occasional disease outbreaks are taken as part ofnormal operation. However, in a widespread outbreak orculling operation where depopulation spans severalvillages, the safety-net herds and flocks kept with relativesmay also be destroyed, leaving no easy means to restock.Even where effective compensation schemes are in place,they seldom cover the cost of lost production time and lostcash flow. In many countries, compensation is limited orfaces considerable administrative challenges, which resultsin payments being inadequate or very delayed.

Distress suffered by farmers over destruction of apparentlyhealthy animals is an additional although unquantifiedimpact of widespread culling. Many farm families in Britainsuffered from psychological shock after the 2001 FMDoutbreak in Britain as did many of the culling teams. Morerecently, scenes of distraught children hiding birds fromculling teams, and farmers refusing to let cullers enter theirvillages, have been a regular feature of HPAI control.

If vaccination reduces culling or the incidence of clinicaldisease, the positive impact on animal welfare can be seenas a benefit in itself, aside from the psychological impacton people who care for livestock. In the CSF outbreak inthe Netherlands in 1997 and 1998 and the FMD outbreak

in the UK in 2001, the large number of animalsslaughtered as well as the high costs of control raised thequestion that much earlier use of vaccination in epidemiccontrol may be appropriate (4). Animal welfare has anincreasing importance in the livestock standards ofMember Countries of the Organisation for Economic Co-operation and Development (OECD) and in premiummarkets for animal products.

At what point, then, should a government decide to bringvaccination into the control process for epidemic disease?An unchecked outbreak of a rapidly spreading disease maykill large numbers of animals. Halting it by means of arapid and effective culling scheme will cause short-termdistress but very little impact on livelihoods in the longterm, particularly if it is possible to provide some form ofcompensation. When it becomes evident that culling willneed to be widespread, or that outbreaks are spreadingbeyond control, a rapid decision to implement ringvaccination may save the livelihoods of many smallholders.In the areas of China with median poultry density, usingring vaccination in a 5 km zone with limited culling tostamp out an HPAI outbreak, instead of culling in a 3 kmzone, has the potential to save the destruction of over50,000 poultry in just one outbreak (38). Vietnam andHong Kong are using targeted vaccination for control ofHPAI, which has reduced both the number of new casesand the scale of culling.

Market shocks from disease outbreaks affect small andlarge producers, but in different ways, and have varyingimpacts according to the disease. Market shocks can becaused by consumer worries leading to loss of demand, byvery severe depopulation, or by closing of markets onanimal health grounds. Zoonotic diseases (i.e. those thatcan affect both animals and people and can be passedbetween them) that cause human death have the greatesteffect on demand, as consumers lose confidence andswitch from eating a product thought to be dangerous toothers considered to be safer. Concern over BSE still closesmarkets from certain exporters (8). HPAI has caused short-term consumption and price drops for poultry in manyaffected countries, and in some countries not yet infected.In some cases the prices of substitute proteins have risen.Other diseases such as brucellosis, tuberculosis andcysticercosis are an accepted daily risk in many countriesand do not create market shocks.

Large exporters have safety nets to deal with immediateproduction losses, but are very concerned about themaintenance of their markets and for reasons alreadydiscussed may prefer not to have vaccination applied.Small-scale operators have limited capacity to deal withloss of animals and the immediate outbreak costs. Large orsmall producers selling into domestic markets may beworried about quarantine measures, which can require


animals to be kept beyond their normal sale time. Pricesmay fall if animals grow beyond a normal weight range,particularly if many are released onto the market at thesame time when quarantine is lifted, and meanwhile the costs of keeping and feeding the animals are higherthan normal.

Can the use of vaccination prevent any of these marketdisruptions?

Using vaccination to control zoonotic disease outbreaks isunlikely to mitigate market shocks caused by consumerfear, unless certification can be provided and consumersare convinced that products from vaccinated animals aresafe to eat. For a purely animal disease, where an outbreakoccurs in an exporting country or zone, there may bebenefits to both export and local markets from usingcontrol methods based on culling rather than vaccination,provided that the outbreak is halted quickly. In Botswana,the export market for beef to the EU from a disease-freezone is an important generator of revenue, and thedomestic market is supplied mostly by local producersoutside the free zone, where vaccination can be used. Thepreviously mentioned CBPP outbreak resulted in a ban onexports of beef to the EU, which proved damaging todomestic producers as well as exporters, because animalsbred for export had to be sold on the domestic market,severely depressing prices (46). Analysis of the Zimbabwebeef sector in 2003 suggested that a similar effect wouldoccur there if an outbreak of FMD closed export markets(27). The decision was made in Botswana to use cullingrather than vaccination because it was believed that thiswould result in the fastest recovery of the export market,and this would be beneficial to all producers.Unfortunately, the outbreak took longer than anticipated tocontrol, and resulted in the destruction of many animalsoutside the export zone (24).

Where the domestic market is the primary market and theexport market is small or non-existent, and particularlywhen disease is endemic, there should be a considerableinterest in using vaccination. Domestic markets do notexclude vaccinated animals provided that they are safe forhumans to consume and the vaccine has been properlyapplied. Vietnam has recently examined its options for thecontrol of CSF. Of all the measures that can be employed,quarantine (which does not permit pigs to be movedoutside of their communes and therefore limits access tomarkets) is the most inequitable, because most of the costis borne by producers while traders have a good chance ofmaintaining their market margins even though their cashflow may be disrupted (20). If several small outbreaksoccur simultaneously (not uncommon), it is moreequitable and less costly to apply ring vaccination ratherthan quarantine. For short-cycle species, if the use ofvaccination makes it possible to keep domestic marketsopen, then it may prove to be very ‘livelihoods-friendly’.

When using vaccination against a zoonotic disease, humansafety and health must be taken into account and thismakes the analysis more complicated. Economic analysisfor human health generally uses a cost utility approach,where the expected rise in the number of quality adjustedlife years (QUALYs) or disability adjusted life years(DALYs) in the population at risk is compared to the costof achieving this result. By contrast, economic analysis oflivestock production systems is more likely to estimate themonetary value of both benefits and costs. Fewassessments of zoonotic disease control have been carriedout that give equal attention to the human and animal side,but two examples are Roth et al. (35) on the control ofbrucellosis in Mongolia and Coleman et al. (5) on thepoverty impacts of zoonotic diseases. Current planning foravian and human influenza control has looked at the costsof each side of the programme but it has been extremelydifficult to make meaningful estimates of total benefits (3),since the risk of a human pandemic, while real, is almostimpossible to quantify. Vaccination of wildlife againstrabies as practised in Western Europe has the effect ofreducing the costs involved in paying compensation tocattle owners as well as the threat to companion animalsand people. In France, vaccination of red foxes was foundto be more effective and cheaper than their depopulationas a way of controlling rabies (2).

Vaccination can also be seen as private or public ‘insurance’to protect livestock. One example from a public perspectivewould be the widespread use of FMD vaccination in the EUuntil 1991, when policy shifted to maintaining diseasefreedom without vaccination. Vaccination is often used byproducers as an insurance against loss of animals or loss ofproductivity, with the relatively small investment invaccination far outweighing the potential reduction inproductivity from disease. Large commercial producers,particularly those in value chains supplying supermarkets,work to tight delivery schedules and cannot afford delayscaused by disease. Even for small producers under lessstringent production requirements, investment invaccination can be financially attractive. For example, inVietnam it can be economically viable for smallholder pigfarmers to pay for CSF vaccination, particularly for theirbreeding sows. The cost of annual vaccination breaks evenwhen incidence is around 2% (20).

The livestock sector is never independent of other sectors,and in some countries models exist that make it possible toestimate the full impact of livestock disease. In Botswana,for example, the cattle sector has positive impacts outsideof agriculture which can be affected by livestock disease(46). In both Thailand (29) and Malaysia, HPAI outbreakscaused a depression in tourism. The 2001 FMD outbreakin Britain had severe negative effects on rural economiesbecause the ban on walking across farmland discouragedlocal tourism and FMD and its control generallydiscouraged international tourism. Approximately


£3.1 million of the total cost is estimated to have beenborne by the public sector and the agri-food sector, withlosses of £4.5 billion to £5.3 billion to other sectors,mainly tourism and leisure (4). Vaccination will be mosthelpful in situations where it reduces the spread of virus,so that the most stringent control measures can be limitedto a small area, or reduces the outbreak time, allowingmovement controls to be lifted sooner. Where animportant tourist industry is affected by a zoonotic disease,human health concerns will take precedence.

Financing vaccinationVaccination is financed from a variety of sources, includingnational governments, international bodies and privateorganisations; cost sharing is quite common. The policy forfunding is usually derived from a mixture of economicconcepts and practicality. Conceptually it may bedetermined on the basis of public and private goods, wherea private good is one that is funded entirely or mostly byprivate individuals (in this case farmers). The conventionalrationale behind this decision is that the ‘good’ in questionhas high excludability (it is easy to prevent people fromusing a service if they have not paid for it) and high rivalry(use of it by one person limits use by others) (11). If it haslow excludability and low rivalry, it is a public good.Alternatively, the externalities generated by an action maybe considered (16). Externalities occur where the actionsof one person have effects on others who are not involvedin the original transaction, but the person causing theproblem is not required to pay compensation for damages.Where high externalities occur and can be traced to asource, it may be possible to apply a ‘polluter pays’principle, but in the case of infectious animal diseases thisis difficult.

It is easy to understand why vaccination against, say,mastitis, or theileriosis might be considered a private good.The presence of mastitis in one herd or flock creates nosignificant externalities. It is possible to make vaccineavailable only to those who pay for it, and in circumstanceswhere supply is limited, use by one person might limit useby others.

Control of a transboundary disease such as CBPP or CSF,seems to be a different case since there are clearexternalities, and it is hard to apply a ‘polluter pays’principle. Controlling it in one herd reduces the risk toneighbouring herds that may not have contributed to thecontrol effort. Nevertheless, Twinamasiko (47) made aconvincing argument that control of CBPP could be treatedas either a private or a public good in different parts ofUganda depending on the prevailing epidemiologicalsituation. Externalities in areas where the disease iswidespread, and where the preference among herders is totreat clinical disease with antibiotic, would be differentfrom those in areas where it seldom occurs.

In Vietnam, where CSF is endemic, its control byvaccination is treated almost as a private good although ithas externalities. Government campaigns are run but notwith sufficient regularity to provide high levels of herdimmunity, and vaccine is available for purchase from thegovernment by private veterinarians for their clients. Insome places it can be bought by farmers or animal healthworkers from local licensed feed and drug shops (15, 20).

Many preventive vaccination programmes have a costsharing element, even when vaccination is delivered bygovernment campaigns. This reduces the strain on limitedgovernment animal health budgets, although government-run cost recovery schemes only transfer costs from onepart of the economy to another without generating anyproduction, while adding administrative charges (13).Payment at point of delivery is a popular way to get costsharing in government vaccination programmes but notwithout problems. In the late 1990s there was a costrecovery scheme for CBPP in Uganda. People distrustedthe vaccine and were unwilling to use it, and an increasingscale of charges over a short time compounded theproblem. Some private practitioners were unwilling torecommend the use of CBPP vaccine because it adverselyaffected customer relations (31). Ring fenced taxation,reciprocal (joint funding) schemes and payment at point ofdelivery, have all been used in the livestock sector.Reciprocal arrangements are used in animal health funds inAustralia, to promote risk sharing.

Generally, it seems that animal owners are prepared to payfor vaccination when they perceive a benefit from it.Leonard (16) cites an example where externalities, ratherthan the private/public nature of the good, would leadUgandan herders to choose vaccination against prevalentepidemic disease (with high private and public benefits)but not to opt for quarantine (with negative private, buthigh public benefits). In the Gambia farmers are willing topay for vaccination against peste des petits ruminants andND when there is an outbreak but less so as a routinepreventive measure (personal communication frommembers of the Veterinary Services). In other situationswhere the risk is perceived differently by differentstakeholders, large commercial producers have opted tocover the costs or even deliver vaccination to smallholdersclose to them, and thereby reduce the risk to their own herds.

It may help to rationalise cost sharing if the direct cost ofvaccination is split into its different elements and eachconsidered separately. Vaccination direct costs can be splitinto sunk or investment costs (including vaccinedevelopment and vaccine delivery infrastructure) andvariable or recurrent costs (including vaccine delivery andvaccine). The investment costs can be made by either thepublic or private sector, or a combination of the two.Public investments are justified for diseases where there are


strong externalities and important social and povertyreduction issues. Public investments could also reduce thecosts of vaccine and its delivery. Payment for variable costsof vaccination depends on the objectives of the diseasecontrol (control or eradication), the disease itself(particularly the externalities it generates) and the systemsin which the disease is found (extensive/intensive;communal or private land ownership). McInerney’s (18)theoretical work paid much attention to the variable costissues at farm-level, but ignored the investment costs. Hisframework has been applied in various studies, forexample in farm-level disease control measures (40), andhas been extended to include fixed costs such as vaccinedevelopment and vaccine delivery infrastructure (9, 44).However, making the best use of investment costs invaccination requires that campaigns be short and sharp inorder to eradicate diseases as quickly as possible (36).Unfortunately, many vaccination campaigns are longprocesses, where herd immunity is developed slowly, andas the impact of disease is reduced, there is less privateincentive to vaccinate. Long campaigns favour returns onthe original investment cost but are not a useful option tosociety. It may even be better to delay vaccination untilvaccine delivery infrastructure is ready and farmer interestis at a maximum so that herd immunity is built up very quickly.

Cost-effectiveness and the delivery processIf vaccination is to be used as part of a disease controlstrategy, it needs to be delivered in ways that are cost-effective (i.e. that minimise the recurrent costs per animalprotected), paying equal attention to the ‘effectiveness’ and‘cost’ sides of the equation. Effectiveness is increased iflivestock owners want vaccination and it is provided in aform and manner that is convenient to the people whomanage the animals and at the same time preserves thequality of the vaccine. Recurrent costs include direct costs(those of getting the vaccine into the animal) as well asindirect costs (lost productivity as a result of vaccination).Direct costs will be reduced if there is a streamlineddelivery chain for getting the vaccine to the people whouse it, while indirect costs are reduced if the vaccine doesnot cause adverse reactions and the vaccination processminimises disruption and stress.

Because some of the direct costs are ‘lumpy’ (they cannotbe broken down into very small units), such as transportand human resources, there may be some economies ofscale attached to mass campaigns, but it is unwise toassume that this will always be true. The cost per protectedanimal will be determined by a number of factors. Somefactors are specific to the vaccine itself: the cost of a dose,the length of time over which it is protective, the way in

which it needs to be applied, the number of doses neededto confer protection and the possibility of side effects. Factors specific to the vaccine interact withfactors for the species and production system. Even wherethere is potential for economies of scale, the animal healthsystem may not have the capability to deliver it, and thereis a need for investment in veterinary services in manyparts of the world (9). The cost of delivering vaccination toan animal under the Pan African Rinderpest Campaignranged from 0.27 to 1.71 ECU, with vaccine making up5% to 33% of the cost (41).

For a cattle or sheep ranching system in Australia or LatinAmerica, the largest element of vaccination cost is that ofcollecting animals together for vaccination. As well as thedirect costs of assembling animals, there are indirect costswhen stressed animals lose weight or even abort fetuses.There are considerable economies in using a vaccine thatneed only be applied once a year, at a time when animalsare being mustered for other activities, and can be giveneasily to semi-wild animals passing through a crush.

For a pastoralist system in Africa, the timing of vaccinationmay be critical. Rinderpest is the only significant livestockdisease to have been almost eradicated. Without thewidespread use of strategic vaccination, it is doubtful thateradication could even have been contemplated. When athermostable vaccine was developed, it became possible tocombine traditional, widespread campaigns using coldchains with unconventional and participatory approachesin remote areas, but institutional factors still hampered thedesign of vaccine delivery. A benefit–cost analysis was used(25) to examine the reasons why pastoralists in northernKenya did not present animals for vaccination, when aneffective vaccine was available that created no adverse sideeffects. The answer was simple: at the time that the studywas carried out, rinderpest in northern Kenya wasoccurring spasmodically, and sometimes in a form that didnot cause high mortality in cattle. Because of theconstraints of veterinary budgets, vaccination campaignswere held at times when animals were widely scattered.Bringing animals to a central vaccination point required atrek across country where cattle raiding was common. Thechance of losing an animal to raiding when bringing it forvaccination was considerably higher than the risk fromrinderpest in an unprotected animal.

Another consideration in pastoralist systems may be aprocess that allows the animal owners or herders toadminister the vaccine, even if this is done under thesupervision of a veterinarian and in a mass campaign, sincethe indirect costs of lost production will certainly be lowerif animals are not stressed. To further reduce indirect costs,a system that allows animals that normally graze togetherto be vaccinated in cohorts will minimise the chances ofbeing infected with other diseases.


Smallholder dairy systems require a different approach.Animals are housed in ways that make them easilyaccessible, in smallholdings that are often close together.Moving them to central vaccination points will result inindirect costs from lost milk production. For private goodvaccines, such as the infection-and-treatment method ofimmunisation against theileriosis, immunisation at homeby a private animal health practitioner or the owner isfinancially optimal. Even where vaccination againstinfectious diseases is provided through public campaigns,it may be preferable to have the animals vaccinated athome through contracts to animal health workers orprivate veterinarians and bear the additional direct costs of delivery.

Monogastric livestock, with short breeding cycles, offerconsiderable challenges in designing vaccine delivery. Toachieve 80% protection against CSF in the smallholder pigpopulation of Vietnam requires three campaigns a year bythe Veterinary Services (20). As an alternative, makingvaccine available at local level, through registeredproviders, gives pig owners the opportunity to vaccinate atthe most appropriate time in the production cycle. Anestablished feed and drug shop that invests in vaccine salescan break even in the second year of sales. Successfuloperation is dependent on farmer confidence andunderstanding of the benefits, assured supply of qualityvaccine and regular inspection to ensure that the coldchain as far as the supplier is maintained. Two provincesthat adopted this approach found that vaccine uptakeincreased, even though owners were asked to pay the fullcost of vaccination when it was privately delivered and only part of the cost when it was provided bygovernment campaigns.

To effectively immunise backyard chickens can requirefour to six campaigns a year, which is clearly impracticalfor Veterinary Services, even in densely populated Asiansystems, where the cost of delivering a dose of vaccine canbe less than US$0.06 (J. Hinrichs, personalcommunication), compared to US$0.38 in rural Africa(10). Recognising this, providers of ND vaccination haveexperimented with vaccines that can be given in feed andwater by the poultry owners. Even for commercial systemswith confined birds, handling individual birds to delivervaccine by needle is time consuming and causesproduction losses, so other means are preferred. Whereproduction cycles make it impractical for governmentVeterinary Services to administer vaccine, the role ofvaccine delivery shifts to the private players in the animalhealth system, leaving the government with the responsibility for quality control and providingimpartial information.

Smallholder cattle, as well as sheep, goats, pigs andchickens, are often owned or managed by women, yet few

vaccine delivery processes are designed with women’srequirements explicitly taken into account. These mightinclude: small numbers of doses in a bottle to reduce cashpayments; delivery to a place near the homestead; trainingwomen to recognise whether the provider has an effectivequality management system; information on vaccine use insomething other than written form, since in somecountries illiteracy is highest in rural women; informationabout vaccination provided to children in schools, sincechildren are often sources of information for their mothersand grandmothers. The Intermediate TechnologyDevelopment Group in Kenya and FARM-Africa inEthiopia deliberately trained female community animalhealth workers and paraveterinarians to work inproduction systems where women normally care for animals.

It has been suggested that research into animal healthtechnology should be measured against a deliverabilitychecklist of accessibility, acceptability, affordability andsustainability in order to make a link from thedevelopment of the technology to the expected economicoutcome of its application (21). The same factors mightprovide a check against the assumptions for effectivedelivery of vaccine. On the supply side, financialsustainability of the delivery is related to the performanceof the value chain for vaccination. Value chain approacheshave been used extensively in manufacturing andhorticulture, and to a lesser extent in the supply oflivestock products, but very little in the analysis of livestock service delivery.

In addition to cost-effectiveness in protecting individualanimals, which is critical for both short, sharp campaignsand longer-term programmes, the economics ofvaccination are affected by the length of time over which itneeds to be applied. Countries that use vaccination as partof an eradication programme, or to maintain an acceptableincidence level of an endemic disease, may be faced withconsiderable recurrent costs over a long period.

Vietnam, intending to commercialise its pig sector andexpand the pork export market, began exploring thepossibility of a disease-free zone in 2002. Between ten andfifty outbreaks of FMD were being reported a year to theOIE, while CSF was considered to be endemic, with anincidence rate below 5% annually. After analysing theproduction and movement patterns of ruminant livestockand pigs, two neighbouring provinces on the north-eastcoast were identified, that might be progressively declaredfree, first of FMD and then of CSF, over a ten-year period.Vaccination was expected to play an important part inremoving CSF from the area. Figure 2 shows the estimatedcosts of the scheme year by year, with a gradual shift inrecurrent costs from vaccination (which was withdrawninto the buffer zone) towards changes in the management


of pigs (chiefly, removal of swill feeding). This patternwould also represent a shift from public to individualprivate costs, since the costs of compulsory vaccinationwould be borne by the government (even if revenues werepartly raised from an earmarked tax on the livestocksector), while management costs would be borne byindividual farmers.

Hong Kong used an enormous and rapid culling operationto control an outbreak of HPAI in 1997, culling allcommercially reared chickens. In 2001 all poultry inmarkets were culled. Since 2002, however, the strategy haschanged to widespread vaccination and limited culling.Vaccination is now compulsory for all poultry, given thatthe risk of virus incursion will continue into theforeseeable future, but it is not being used in isolation, asstrict biosecurity and surveillance measures have beenintroduced at markets and retail points. The number of poultry farms is gradually being reduced through exgratia payments to farmers who surrender their farmlicences (38).

The examples in this paper suggest that decisions aroundthe use of vaccination are seldom clear-cut and benefitfrom a wide range of information about the economic andinstitutional conditions of the livestock sector. The finalsection examines constraints in applying economicassessment to the planning of animal vaccination andhighlights areas that would benefit from further work.

ConclusionsDecision makers faced with emerging and recurringdiseases need good decision support tools to decide whenit makes economic sense to deploy vaccination; theseshould include not only epidemiological and economicmodels, although these are important, but informationabout consumer and producer behaviour that underpinsthe assumptions made by modellers. Ideally, they wouldhave access to tools applicable for several species,adaptable for different types of major disease, to assess theprobability of risk under a range of situations, as well as upto date production, price and trade data, and agreedpriorities for different stakeholders against which tomeasure predictions. These conditions are rarely in placein advance of a crisis, and may not be met even when alonger planning horizon is available. Animal healthplanners, like planners in other sectors, are forced to make‘satisficing’ decisions that make the best use of the availabledata in a limited time span. Most of the published work onthe economics of animal health is based on problems thathave already passed, although they carry lessons for the future.

The examples described in this paper, together withcomparable analyses for other animal health problems,suggest certain imperatives for social scientists chargedwith supporting the development of animal healthsystems.

a) It is never too early to make contingency plans. Even foremerging diseases with no vaccines currently available, it ispossible to develop risk assessments and computer modelsand carry out sensitivity analysis for different prices andprotection levels. There is a growing need to balance theneeds of different stakeholders as livestock marketsbecome more globalised, and this means that questionsabout the use of vaccination need to be asked early in theplanning process. Public opinion on animal welfare, andconcerns about loss of livelihoods, have thrown upquestions about the automatic use of widespread culling tocontrol outbreaks. However, vaccination programmes mayrequire prior investment in the animal health system.

b) We are not beginning from zero. There have been morethan twenty-five years of work in combiningepidemiological and economic models to analyse animalhealth programmes, including vaccination, in cattle, pigand poultry systems. While models always need to beadapted to make them situation-specific, a lot is nowknown about developing quantitative tools. However,there are only rare examples of the same tools being re-used or further developed. It is time to examine carefullythe role that models play in the animal health planningprocess and whether they might be better used. Someinitiatives have been taken in this direction (14, 42).


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Fig. 2Costs of establishing a classical swine fever and foot andmouth disease free zone in two provinces of VietnamSource: Taylor et al., 2003 (43)

c) Animal health economics has placed a lot of emphasison quantitative modelling. There is a need now to placeequal emphasis on the assumptions underlying models,which result from social and political conditions andinstitutional arrangements. Animal health economists canalso borrow from business analysts, using tools such asvalue chain analysis to revisit the design of animal healthsystems and the delivery of vaccination and other inputs.Work has been done in all of these areas analysing theseconditions, but we have yet to develop planning teams thatare truly multi-skilled or contain people with ‘T-shaped’skills (i.e. a strong grounding in one disciplinary area, andsufficient training or experience in others to becomfortable with problems that cut across severaldisciplines).

d) Some specific areas would benefit from more attention.One would be a review of the economics of vaccinationunder the latest regulations, including the use of DIVA.There would also be value in developing more country andproduction system specific models to decide when toswitch to vaccination, and applying them with a range ofcultural and institutional assumptions, since outbreaks of notifiable diseases are prone to taking longer thananticipated to control, and having a more costly impact

than expected. Given the rise in emerging zoonotics, andthe increasing interest in food safety in most countries,these areas may require more attention in the future.Finally, there is room for a more detailed review of ways tomake vaccination more cost-effective. These may includeregional co-operation in vaccination task forces, andincreasing use of animal health workers and privateindividuals in vaccine delivery, with a variety oforganisational structures.

This is an interesting time for animal health economists.With a body of knowledge on which to build, technologyto assist with analysis, and increasing understanding of theimportance of many different aspects of social science inplanning and policy making, there are excellentopportunities to fine tune the planning of animal health,including the use of vaccination, to make it user-friendlyand cost-effective under many circumstances.


Économie de la vaccination animale

A. McLeod & J. Rushton

RésuméLes auteurs proposent une méthode permettant d’évaluer pas à pas le bien-fondé économique de la vaccination en tant qu’outil de lutte contre les maladiesanimales et de vérifier le financement et la gestion des campagnes devaccination. Ils décrivent les mesures qui ont été prises pour préserver lecommerce international et abordent d’autres questions liées à la protection desmoyens d’existence. Quel que soit le motif à l’origine de la vaccination, lessecteurs public et privé devraient en partager les coûts. Pour que la vaccinationsoit rentable, il convient de prévoir des modes d'administration adaptés auxsystèmes de production animale. Les auteurs concluent en soulevant un certainnombre de questions économiques liées à la vaccination, qui mériteraient unexamen plus approfondi.

Mots-clésÉconomie – Maladie animale – Moyen d’existence – Vaccination.

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Aspectos económicos de la vacunación animal

A. McLeod & J. Rushton

ResumenTras explicar los pasos que cabría seguir para valorar la conveniencia, desde elpunto de vista económico, de utilizar las vacunas para controlar una enfermedadanimal, los autores describen el modo en que se financia y gestiona la vacunación. Después exponen las decisiones que se han adoptado conrespecto a la protección del comercio internacional y a temas relacionados conla salvaguarda de los medios de subsistencia. Con independencia de los motivosque subyazcan a la vacunación, en general cabe repartir sus costos entre el sector público y el privado. Para una campaña rentable se necesitan métodospara administrar la vacuna adaptados a los sistemas de producción ganadera.Los autores concluyen proponiendo una serie de temas ligados al uso de la vacunación que merecerían un análisis económico más detenido.

Palabras claveAspectos económicos – Enfermedad animal – Medio de subsistencia – Vacunación.

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42. Taylor N.M. & James A.D. (2003). – Comparison of two caseswhere epidemiological modelling was used to supportdecisions regarding foot-and-mouth disease control in UK. In Proc. 10th Symposium of the International Society ofVeterinary Epidemiology and Economics, 17-21 November,Santiago, Chile.

43. Taylor N.M, McLeod A., Thuy N.T., Stone M., Binh V.T., Lan L.T.K., Dung D.H. & Barwinek F. (2003). – Examiningthe options for a livestock disease-free zone in the Red RiverDelta of Vietnam. Strengthening of Veterinary Services inVietnam (SVSV). ALA/96/20. Supported by the EuropeanCommission.

44. Tisdell C.A. (1995). – Assessing the approach to cost-benefitanalysis of controlling livestock diseases of McInerney andothers. Research papers and reports in animal healtheconomics, No. 3, Department of Economics, University ofQueensland, Brisbane.

45. Tisdell C.A. (1996). – Economics of investing in the health oflivestock: new insights? Research papers and reports inanimal health economics, No. 29, Department of Economics,University of Queensland, Brisbane.

46. Townsend R., Sigwele H. & MacDonald S. (1998). – Theeffects of livestock diseases in southern Africa: a case study ofthe costs and control of cattle lung disease in Botswana. Paperprepared for the 1998 Conference of Economic and SocialResearch Council Development Economics Study Group, theUniversity of Reading, July 1998.

47. Twinamasiko E.K. (2002). – Development of an appropriateprogramme for the control of contagious bovinepleuropneumonia in Uganda. PhD Thesis R8842, Universityof Reading, UK.

48. Upton M. (1989). – Livestock productivity assessment andherd growth models. Agric. Syst, 29, 149-164.

49. Upton M. (1993). – Livestock productivity assessment andmodelling. Agric. Syst., 43, 459-472.

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Animal vaccination and the evolution of viral pathogens

K.A. Schat (1) & E. Baranowski (2)

(1) Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca,NY 14853, United States of America(2) UMR INRA-ENVT 1225, Ecole Nationale Vétérinaire de Toulouse, 31076 Toulouse, France

SummaryDespite reducing disease, vaccination rarely protects against infection andmany pathogens persist within vaccinated animal populations. Circulation ofviral pathogens within vaccinated populations may favour the development ofvaccine resistance with implications for the evolution of virus pathogenicity andthe emergence of variant viruses. The high rate of mutations during replicationof ribonucleic acid (RNA) viruses is conducive to the development of escapemutants. In vaccinated cattle, unusual mutations have been found in the majorantigenic site of foot and mouth disease virus, which is also involved in receptorrecognition. Likewise, atypical changes have been detected in theimmunodominant region of bovine respiratory syncytial virus. Largedeoxyribonucleic acid (DNA) viruses are able to recombine, generating newgenotypes, as shown by the potential of glycoprotein E-negative vaccine strainsof bovine herpesvirus-1 to recombine with wild-type strains. Marek’s diseasevirus is often quoted as an example of vaccine-induced change in pathogenicity.The reasons for this increase in virulence have not been elucidated and possibleexplanations are discussed.

KeywordsEvolution – Marek’s disease – Pathogenicity – Pathotype – Receptor – Tropism – Vaccine– Virulence – Virus.

IntroductionThe production of animal proteins for humanconsumption depends on the reduction or elimination ofdiseases, which can cause losses directly throughmorbidity and mortality, and indirectly through increasedcondemnations at processing plants, decreased growthrates and/or increased susceptibility to other pathogens.The tendency towards increases in size of production units,often associated with the presence of multi-age groups ona farm, complicates the control of pathogens. Thedevelopments in the poultry industry provide an excellent

example of the increase in size of production units, withsome farms having over one million layers producing eggsfor consumption. Although the introduction of manypathogens can be reduced by applying strict biosecuritymeasures, including the use of filtered-air positive pressurehousing, the associated costs often make this approachimpractical. The development of veterinary vaccinologyhas been essential in providing cost-effective approaches toprevent and control infectious diseases in animals. Besidesimproving the animal health sector, animal vaccination hasalso substantially enhanced public health by preventingthe occurrence of several zoonotic diseases, and reducingthe use of veterinary drugs and hence drug residues in the

food chain (38). Recent advances in vaccinology havedefined new directions for vaccine development strategies,and new generation vaccines are rapidly gaining scientificacceptance (22, 49, 56). Nevertheless, the rapiddevelopment of new veterinary vaccines, and theirwidespread use to protect large populations of animalsagainst a growing number of infectious diseases, haveraised questions about the potential consequences of massvaccination strategies for the evolution of pathogens, inparticular rapidly evolving viruses.

Because of high population numbers, rapid replicationcycles and elevated mutation rates, viral pathogens exhibitan important capacity for variation and adaptation. This isparticularly true for ribonucleic acid (RNA) viruses, whichlack proofreading capability and replicate at maximumviable mutation rates. Mutation rates during RNAreplication have been estimated to be in the range of 10-3

to 10-5 errors per nucleotide copied (Fig. 1). As aconsequence of such limited replication fidelity, individualRNA genomes have only a fleeting existence, and RNAviruses evolve as heterogeneous populations of variantgenomes collectively termed viral quasispecies (12, 13,15). Viral genomes within quasispecies are subjected to acontinuous process of variation and competition. Genome

subpopulations best adapted to replicate in a givenenvironment will dominate the population, while unfitmutants are kept at low levels. Unfit mutant populations inone environment may nevertheless be fit in a differentenvironment, and modulation of frequencies of genomesubpopulations is the key to adaptability of RNA viruses.The biological and medical relevance of the quasispeciesdynamic of RNA viruses has been extensively documentedin several recent publications (12, 13, 15). Althoughseveral small deoxyribonucleic acid (DNA) viruses canreach evolution rates similar to those of RNA viruses,elevated mutation rates would be incompatible with themaintenance of the genetic information contained in largeDNA viruses with complex genomes over 100 kilobases(kb) in size. Large DNA viruses are thus less prone to errorthan RNA viruses (Fig. 1). Acquisition of new geneticinformation proceeds mainly by gene duplication, lateralgene transfer by recombination between related viralgenomes, and host gene capture (47).

Besides important differences in their genetic organisation,viruses can also produce a wide range of clinicalmanifestations upon replication in their hosts. Viralinfections may be inapparent or they may cause acute orchronic diseases either directly, as a result of viralreplication in infected tissues, or indirectly by triggeringimmunopathological responses (33). Many viral and hostfunctions, as well as environmental factors, are presumedto influence the outcome of an infection. It is thereforeoften difficult to determine the nature of virus–hostinteractions responsible for these disparate effects. Anumber of recent studies involving several importantanimal pathogens, such as bovine respiratory syncytialvirus (BRSV), foot and mouth disease virus (FMDV),bovine herpesvirus-1 (BoHV-1) and Marek’s disease virus(MDV), have provided evidence that evolution of viralpathogens within vaccinated populations has not onlyimportant implications for the development of vaccineresistance, but may also promote the emergence of variantviruses with altered pathogenicity or host tropism.

In this review we will discuss some of the factors that maydrive the development of pathogens with modifiedpathogenicity in vaccinated populations. The developmentof vaccine resistance to MDV will be examined in detailbecause MDV vaccines provide the best example ofchanges in field strains in association with vaccination.Marek’s disease (MD) vaccines are probably the mostintensively used vaccines against a DNA virus in anyspecies. In the United States of America (USA) aloneapproximately 10 billion chickens are vaccinated againstMD every year and at least an equal number of chickensare vaccinated elsewhere in the world. Moreover, theemergence of MDV strains with increased pathogenicity isoften quoted as an example of vaccine-driven evolution ofa DNA pathogen (18, 19, 39).


RNA viruses

DNA viruses

Bacteria and yeast

Genome size

1 kb 10 kb 100 kb 1 Mb 10 Mb

DNA genomes ( >100 kb) RNA genomes

Mutation frequencies

10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3

Fig. 1Genome sizes and mutation frequencies for DNA and RNAmicroorganismsThe tolerance of DNA and RNA microorganisms to accept mutationsdecreases with genome size. RNA viruses are confined to one logvariation in genome size and display average mutation frequencies of 10-4 errors per nucleotide copied (14). DNA viral genomes span morethan 2.5 logs in size, overlapping the smallest bacterial genomes suchas Mycoplasma genitalium (580 kb). The evolution rate for DNA viruseswith small genomes varies from 10-4 (parvovirus) to 10-8 (papovavirus)substitutions per nucleotide per year (14), while the rate is estimatedat 3.5 � 10-8 for large DNA viruses such as human herpesvirus-1 (152 kb) (42)

Imperfect vaccinesAlthough vaccination allows control of the clinicalmanifestations of a disease, vaccine-induced immunitygenerally does not protect against viral infections, andlimited virus replication and shedding can still be observedin vaccinated animals. Optimal protection of eachindividual within large populations is also generally notachievable by mass vaccination strategies, because the levelof protection conferred by vaccination can be influencedby multiple factors, the most important being:

– damage to vaccine

– improper administration

– immaturity of the host immune system

– inhibition by maternal antibodies

– immunosuppressed state of the host

– enhanced susceptibility of the host

– insufficient time between vaccination and exposure

– antigenic differences between circulating viruses andvaccine strains

– development of vaccine resistance.

Thus, in the absence of sterilising immunity, or as aconsequence of sub-optimal protection, many pathogensstill persist within vaccinated populations.

The selective pressure that vaccine-induced immunity mayexert on evolving pathogens is largely unknown. A recentanalysis of the genetic diversity of BRSV strains, using alarge collection of field isolates, revealed a continuousevolution of BRSV, especially in countries wherevaccination is widely used. Remarkably, unusual mutationsmapping within the conserved central hydrophobic part ofthe G attachment protein of BRSV were observed in somerecent French isolates (55). The biological significance ofthese mutations in the immunodominant region of BRSV Gprotein is not known, but they may contribute to the lackof cross-protection between vaccine and field isolates (55).Another example of interaction between vaccine-inducedimmunity and the genetic diversity of RNA viralpopulations replicating in the animal host is provided by alarge-scale challenge experiment with FMDV in peptide-vaccinated cattle (52). Synthetic peptides conferred onlypartial protection, and some immunised animalsdeveloped lesions upon challenge with virulent virus.FMDV mutants escaping neutralisation in peptide-vaccinated animals were characterised by unusual singleamino acid substitutions affecting both virus antigenicstructure and receptor-binding specificity (Fig. 2) (4, 6, 52, 53).

The risk of recombination between attenuated or vectoredviral vaccines and their wild-type counterparts in co-

infected animals is generally considered to be a majorsafety concern for the development and use of livevaccines. The consequences of co-infections were recentlyassessed in a series of studies involving thealphaherpesvirus BoHV-1. These studies revealed thatBoHV-1 exhibits a high potential for genetic diversificationin co-infections of the animal host and that recombinationis an important mechanism in alphaherpesvirus evolution(46). Several European countries have initiated controlprogrammes based on the use of marker vaccines in whichthe gE gene of BoHV-1 has been deleted. These markervaccines, combined with serological detection of gE-specific antibodies, allow differentiation between naturallyinfected and vaccinated animals. Remarkably, virulentBoHV-1 recombinants carrying the vaccine gE-negativephenotype can be generated in vitro by co-infection ofattenuated gE-negative with virulent gE-positive BoHV-1strains (35, 36). As live attenuated marker vaccines can beadministered intranasally, at the natural portal of entry ofBoHV-1, co-infections between marker vaccine strains andwild-type BoHV-1 can be encountered under naturalconditions. This suggests the potential for emergence ofrecombinant BoHV-1 with the virulence of the wild-typestrain and the phenotype of the vaccine strain (54).

Recent epidemiological evidence supports the hypothesisthat oncogenic strains of MDV evolve towards pathotypes


Fig. 2Exploration of new antigenic/receptor binding structures by foot and mouth disease virusThe overlap between antibody and receptor-binding sites at the surfaceG-H loop of capsid protein VP1 of foot and mouth disease virus (FMDV)favours the co-evolution between antigenicity and cell tropism in thisimportant animal pathogen. The emergence of unusual FMDV variantsdisplaying both altered antigenicity and modified host cell tropism hasbeen reported in different biological situations including the selection of monoclonal antibody resistant mutants in baby hamster kidney (BHK) cells (31, 41), challenge experiments in peptide-immunised cattle (52, 53), and virus adaptation to the guinea pig (5, 37). The aminoacid sequence of the capsid protein VP1 G-H loop region corresponding to antigenic site A of FMDV C-S8c1 is indicated in black boxes. The Arg-Gly-Asp (RGD) integrin-binding motif and flanking amino acid residues promoting FMDV serotype C binding to BHK cells aredesignated by white-framed boxes (32). Single amino acid replacementsfound in antigenic site A of FMDV variants are listed for each position

BHK cells

136 – Y T A S A R G D L A H L T T T – 150

D R G R G V V R PN G E S L

N P I

Cattle

A S A R G D L A H L

G P P

Guinea-pig

A S A R G D L A H L

P

with increased virulence, and this evolution is probablydriven, at least in part, by MD vaccination (59, 60, 61).However, there are many factors involved in optimal MDvaccination, which will be discussed in detail in the section‘Marek’s disease: a case study on evolution of virulence’.

Although it is often difficult to predict the consequences atthe population level of mechanisms evidenced at theanimal level, these different studies suggest that circulationof pathogens within vaccinated populations may have anumber of implications for the development of vaccineresistance, the evolution of virus pathogenicity, and evenfor the emergence of mutant viruses with altered tissue orhost tropism.

Antigenic variation and shifts in receptor usageDespite early evidence that antigenic changes in influenzavirus haemagglutinin could be linked to modifications insialic acid recognition (50), it is commonly assumed thatantibody-binding sites and receptor recognition motifs onvirus particles are physically separated. The mainargument is that amino acid residues involved in receptorrecognition should be invariant, as variation would belethal, while antigenic sites are inherently variable to allowthe virus to cope with the host antibody response. Incontrast to this conventional wisdom, structural studieshave shown that there is some overlap between these tworegions in a number of viral systems, including FMDV (5, 6, 57).

In FMDV, amino acids which are critical for the recognitionof integrin receptor molecules, in particular the highlyconserved Arg-Gly-Asp (RGD) motif located at theprotruding G-H loop of capsid protein VP1, are alsoinvolved in the interaction with multiple neutralisingantibodies (14, 17). Although integrins are probably themajor class of receptor molecules used by FMDV in theanimal host, virus evolution in cell culture can renderRGD-dependent interactions dispensable for infectivityand develop alternative pathways to recognise and entercells (17, 24). Because the RGD motif located at the G-Hloop of capsid protein VP1 is also a key part of severalepitopes recognised by neutralising antibodies, thecapacity of FMDV to develop and use RGD-independentmechanisms of cell recognition has considerableimplications for the evolution of virus antigenicity. WhenFMDV entry into cells is restricted to RGD-dependentinteractions, the amino acid residues which are criticallyinvolved in integrin recognition remain invariant whilemutations in flanking residues allow the virus to escapeimmune surveillance. This situation changes dramatically

upon FMDV acquisition of RGD-independent mechanismsof cell recognition. The relaxation of the constraintsimposed by integrin recognition allows FMDV to explorenew antigenic structures at the G-H loop of VP1, andvariant viruses with highly unusual substitutions, such asArg-Gly-Gly (RGG) or even Gly-Gly-Gly (GGG) sequencesinstead of the RGD, can be selected (31, 41). This providesFMDV with a new repertoire of antigenic variants and animproved capacity to escape neutralisation (Fig. 2).Absence of integrin recognition by FMDV harbouringaltered RGD motifs has confirmed that changes in FMDVantigenic structures can be linked to modifications inreceptor usage, and suggests that viruses which use thesame surface site for receptor recognition and antibodybinding harbour the potential for co-evolution ofantigenicity and receptor usage (5, 6, 53).

The concept of a receptor binding site accessible toantibodies may also have important implications foradaptation of FMDV in the field. The genomic changes thatcan endow FMDV with the capacity to use alternativemechanisms of cell recognition are minimal (5, 6), andantigenic variants with altered receptor-bindingspecificities are likely to be present in the mutant spectrumof FMDV replicating in the animal host. A recent studyanalysing the genetic changes selected during adaptation ofFMDV to guinea pigs documented the progressivedominance of an unusual amino acid replacement affectingboth the antigenic structure of the G-H loop of VP1 and itsinteraction with the integrin molecules expressed invarious cell lines commonly used to propagate FMDV (Fig. 2) (4, 37). Remarkably, the antigenic alteration foundin the guinea pig-adapted virus was also identified inseveral FMDV mutants escaping neutralisation by anti-FMDV antibodies in peptide-vaccinated cattle (Fig. 2) (52,53). These results with FMDV mutants generated in vivoillustrate the high potential for RNA virus adaptation in theface of an immune response.

Marek’s disease: a case studyin evolution of virulenceVirulence, the capacity of a pathogen to cause disease, is aphenotypic trait which is subjected to variation and naturalselection. MDV provides an excellent example of variationin its potential to cause different disease syndromes andnatural selection towards increased virulence. Since thefirst description of polyneuritis in four roosters by JózsefMarek in 1907 (29), MDV has shown a propensity to causea number of different disease syndromes includinglymphoproliferative syndromes, commonly referred to asMD, lymphodegenerative disease, central nervous systemdisease syndromes, and atherosclerosis (65). Selection for


increased pathogenicity was already noticed beforevaccines were introduced in the early 1970s. The changesin the broiler industry in the 1950s had two importantconsequences. First of all, the housing system changed,with a drastic increase in the density of chickens per squaremetre. The birds were also subjected to intensive geneticselection to improve production parameters. During thesame period a dramatic increase in MD incidence occurred(8) and the term ‘acute MD’ was introduced. It isimpossible to prove if this change in pathogenicity wascaused by a change in the virus, a change in the genetics ofthe host, a change in the environment of the host or acombination of these factors. The incidence of MDcontinued to increase in broilers, with condemnationsreaching approximately 3% in Delmarva (a peninsula inthe USA encompassing Delaware, Maryland and Virginia)and Georgia, until the herpesvirus of turkeys (HVT)vaccine became available around 1970. Since theintroduction of MD vaccination in the USA, there havebeen two periods with increased MD condemnations,which were first noted in Delmarva. The first one, in theearly 1980s, led to the introduction of the bivalentHVT+SB-1 vaccine. The second occurred in the mid 1990sand led to the introduction in the USA of the CVI988vaccine (40), also known as ‘Rispens’. The increase incondemnations in the early 1980s was significantly lowerthan the level of condemnations before the introduction ofvaccines, and the second spike was again lower than thefirst one. Notwithstanding these spikes in condemnations,MDV vaccines are still highly effective in preventing thedisease (9, 62). In 2002, MD condemnations were ingeneral less than 0.001% in the USA, althoughcondemnations may be higher in some regions, e.g.Delmarva, which had a condemnation rate of 0.011% in2002 (34). Worldwide there are few problems reported atthis time (20, 34). Spikes in condemnations are sometimesseen in various parts of the world, but these may be causedby many factors and do not necessarily indicate thepresence of more virulent strains.

Economic considerations

Before discussing some of the biological factors ofMDV–host interactions it is important to address man-made factors influencing these interactions. The poultryindustry provides the best example to illustrate some of theproblems preventing optimal vaccine-induced protectionin production animals. Primary chicken lines are undercontinuous selection for improved productioncharacteristics, in which selection for disease resistanceconstitutes only one of the many components. Theconsequence is that the host is continually changing,which may impact virus–host interactions. In the USAprofits per broiler are minimal and highly variable fromyear to year. Over the last five to six years profits for

broilers have ranged from approximately $0.10 to actuallosses of approximately $0.01 per pound (0.45 kg) (J. Smith, personal communication). As a consequence thepressure to reduce costs is high. The down-time betweenproduction cycles is approximately 14 days in the USA (J. Smith, personal communication) and litter is frequentlyre-used for a number of cycles (34), thus providing animmediate challenge to newly placed birds before adequateacquired immune responses have developed. MD vaccinesare some of the more expensive used in broilers, withaverage prices in the USA ranging from $2.25/1,000 dosesfor HVT to $10.75/1,000 doses for HVT/CVI988. Toreduce costs these MD vaccines are routinely used at halfor one quarter of the recommended dose in broilers,although these vaccines are used at the recommendedlevels in layers and broiler breeders. Although there aredifferences between the USA and other major poultryproduction areas of the world, the general trend to reducecosts leads to improper vaccination techniques andinadequate biosecurity, thus increasing the risk of selectionfor strains with increased pathogenicity.

Nomenclature of Marek’s disease virus strains

Marek’s disease virus is generally referred to as serotype 1MDV (MDV-1), and all MDV-1 strains have oncogenicpotential unless the strains are attenuated in cell culture(65). Serotype 2 MDV (MDV-2) strains are non-oncogenicchicken herpesviruses, while serotype 3 consists of HVT.These three serotypes belong to the recently establishedMardivirus genus within the Alphaherpesvirinae subfamilyof the Herpesviridae (http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/index.htm [accessed on 20 September2006]). Witter et al. (58, 63) have developed a system todetermine the pathotype of MDV-1 strains isolated fromvaccination breakdowns. Briefly, genetically definedchickens (line 15 � 7), positive for maternal antibodies forthe three serotypes and vaccinated with HVT or HVT+SB-1 (a MDV-2 strain), are challenged with virus strains withknown pathogenicity and with the new strains. Dependingon the development of MDV in the groups vaccinated withHVT or the bivalent vaccine, new isolates are classified asvirulent (v), very virulent (vv) or very virulent plus (vv+)MDV. European strains are sometimes classified ashypervirulent, which is probably comparable to the vv+classification in the USA.

Pathogenesis of Marek’s disease

The pathogenesis of MD has been extensively reviewed andfurther references can be found in these reviews (2, 10).Infection occurs by inhalation of cell-free virus and isprobably transferred to B lymphocytes by phagocytic cells.Until recently, macrophages were generally considered tobe resistant to MDV infection and replication, but Barrow


et al. (7) provided support for the role of macrophages bydemonstrating the presence of MDV transcripts in thecytoplasm and nucleus of splenic macrophages afterinfection with a hypervirulent strain of MDV. However,virus particles could not be demonstrated in the nucleusand it is not known if the presence of transcripts representsan abortive or productive infection. The first lyticreplication phase mainly occurs in B cells, although someT cells can also be involved. The lytic phase can normallybe demonstrated as early as three to four days postinfection (PI). Subsequently, activated T cells expressingmajor histocompatibility complex (MHC) class II and CD4become infected with MDV, while resting T cells appear tobe refractory to infection. Around seven days PI, latentinfections are established in the activated T cells.Depending on factors such as genetic resistance of the host,virulence of the MDV strain, vaccination status andpresence of immunosuppressive viruses, tumours maydevelop mostly in CD4+, MHC class II+ T cells.

Infectious virus is produced in the feather follicleepithelium (FFE), and shedding of MDV starts around 14days PI, which is before the onset of MD mortality,although experimentally infected birds may die within thisperiod with the early mortality syndrome (65).Quantitative polymerase chain reaction (qPCR) assays havebeen developed to measure MDV genome copies in theFFE, and initial data suggest that peak shedding occursbetween two and five weeks PI (1, 3, 23), although viralDNA has been detected as early as seven days PI (3).

Marek’s disease vaccines, applications and protective mechanismsSince the introduction of HVT in the USA in the early1970s, ‘new’ vaccines or new combinations have beenintroduced twice in the USA. In 1983 the bivalentcombination HVT+SB-1 became available, and CVI988was licensed in 1996 to protect against field viruses withincreased pathogenicity (Fig. 3). However, CVI988, whichis currently considered the ‘gold standard’ for MD vaccines(9), has been used in the Netherlands since 1971 andafterwards in other European countries (see 34 for details).Thus, since the introduction of MDV-2 strains (SB-1 and301B) no new MDV vaccines have been developed that arebetter than CVI988. Witter and Kreager (64) found thatnew vaccine strains could be obtained that werecomparable to, but not better than, CVI988. They actuallyquestioned if the efficacy of MD vaccines is limited bysome, unspecified, type of biological threshold.

Vaccine-induced immunity protects against viralreplication, resulting in a significant reduction of the lyticreplication phase of the challenge virus (43). However,vaccination does not prevent the establishment of infectionin the lymphoid organs nor, and more importantly, in the

FFE. Interestingly, qPCR studies suggest that vaccinationwith HVT does not reduce shedding of MDV-1 at 56 daysPI (23). Additional studies are needed to determine ifdifferent pathotypes differ quantitatively in virus sheddingand if this is modified by vaccination.

Are virulence- and transmission-related traitsIinked to pathogen fitness in Marek’s diseasevirus?

Although it has been clearly shown that more virulentMDV pathotypes have evolved since the introduction ofvaccines, the molecular basis for the evolution of MDV hasnot been elucidated (45). Early virus replication innonvaccinated birds is prolonged for more virulentpathotypes compared with less pathogenic strains (66) andis higher in nonvaccinated than in vaccinated birdsindependent of the pathotype (43), suggesting that theevolution of MDV is related to the early virus–hostinteraction, perhaps by interference with immuneresponses. However, genes important for viral replication,e.g. viral interleukin (vIL)-8, pp38 (11, 21, 26) and severalglycoproteins, are highly conserved across pathotypes (25, 48), which is of interest because these genes, with the


1940 1960

Rela

tive

viru

lenc

e

Years

m

v

HVT

BIVAL

RISPENS

vv

(vv+)

1980 2000

m: mildv: virulentvv: very virulentvv+: very virulent plus (hypervirulent)HVT: herpesvirus of turkeys vaccineBIVAL: bivalent HVT+SB-1 vaccineRISPENS: CVI988 vaccine

Fig. 3Evolution of Marek’s disease virus isolates. Stepwise evolution of virulence of Marek’s disease virus isolates: past history and future predictions. There seems to be a relationshipbetween introduction of new vaccines and the development of morevirulent pathotypesFrom (59), with permission of Taylor and Francis Ltd (http://www.tandf.co.uk/journals)

exception of vIL-8, are recognised by cell-mediated and/orhumoral immune responses (30, 44). Mutations in theMeq gene correlating with virulence were described byShamblin et al. (48). These authors argued that Meq is nota likely target for vaccine-induced selection because theMeq gene is not encoded by HVT or SB-1 and Meq ismostly expressed during latency and in transformed cells.Moreover, deletion mutants for Meq can cause cytolyticinfections comparable to infection with wild-type virus,but do not cause tumours (28).

Gandon and colleagues (18) have suggested that vaccinesreducing the growth rate of a pathogen, e.g. MD vaccines,would lead to evolution of the pathogen towards increasedvirulence, while vaccines blocking infection would notinduce such effects and may even lead to decreasedvirulence. They also suggest that virulence andtransmission are related traits intimately linked topathogen fitness (39), although this hypothesis is notgenerally accepted (16). If this hypothesis is correct, itwould suggest that the more virulent MDV pathotypesshould be more efficient in virus shedding from the FFEthan less virulent pathotypes. As was mentioned before,there is a lack of quantitative data on MDV shedding fromthe FFE. Baigent et al. (3) quantitated the number ofCVI988 genome copies in FFE from different commercialchicken breeds and found differences between the breeds,but comparative studies with other pathotypes have notyet been reported. However, there may not be an intimatelink between virulence and transmission in MD, based onstudies using deletion mutants. Very virulent MDV orvv+MDV mutants lacking the pp38 gene (21), vIL-8 gene(11) or the first intron of vIL-8 (26) show a significantreduction in lytic virus replication and a subsequentreduction in tumour incidence, probably as a consequenceof reduced virus load. However, these viruses do producecell-free virus in the FFE (11, 21). It will be important toconduct quantitative studies to determine if the amount ofvirus in the FFE is directly related to replication of mutantviruses in the lymphoid organs and if there are quantitativedifferences between wild-type and mutant viruses in theamount of virus produced in the FFE.

The future of Marek’s disease protection

Based on past experience it is expected that more virulentpathotypes than vv+ strains of MDV will emerge. Based onthe work by Witter and Kreager (64) it is less certain thatimproved vaccines will be available in the near future.Recombinant fowlpox virus (rFPV)-based vaccinesexpressing MD glycoproteins have shown some promiseunder experimental conditions (27). Based on experienceswith rFPV vaccines for avian influenza (51) it is not clear ifthese vaccines will give sufficient protection if chicks arepositive for FPV maternal antibodies. In addition, in order

to be used by the industry any new vaccine must be cost-effective, reducing MD contamination at a cost comparableto current vaccine prices.

Future strategies for protection against MD may have todepend on a combination of vaccination, increased geneticselection, and perhaps transgenic approaches. All currentcommercial and experimental vaccines are based on thereduction of virus replication rather than prevention ofinfection. It is not known if vaccines preventing MDVinfection can be developed. To be successful these vaccinesneed to block entry of virus into phagocytic cells, whichmay be complicated by the nature of cell-free virusproduced in the FFE. Most, if not all, cell-free virusparticles are encased in keratin, and vaccines designed toblock virus–cellular receptor interactions may thereforenot work. Mechanisms to block virus replication afterentry into susceptible cells (using macrophages, B cells,activated T cells, epithelial cells) may be possible usingRNA interference (RNAi) approaches. Transgenicapproaches, which may not be acceptable to consumers,will be needed to express the RNAi sequences in allpotential target cells.

ConclusionIn a global economy with open markets and frequentexchanges of animals and livestock products, the control ofinfectious diseases has become a major concern for thefarming industry. Vaccination, when available, is probablythe most effective method of protecting animal populationsagainst economically relevant pathogens, and massvaccination strategies have largely contributed to thecontrol of infectious diseases in endemic areas.

Despite reducing the clinical manifestations of the disease,vaccination rarely protects against viral infection, andmany pathogens still persist within vaccinatedpopulations. Epidemiological studies have documented arapid and continuous diversification of different viralpathogens in large populations of animals protected byvaccination, suggesting that the evolution of thesepathogens was probably driven, at least in part, byvaccination. The biological implications of vaccine-drivenevolution of viral pathogens remain largely unknown, andrecent evidence suggests that the development of vaccineresistance may also be associated with modifications inpathogenicity or host tropism, as illustrated by theemergence of MDV pathotypes of enhanced virulence andthe selection of FMDV variants with modified receptor-binding specificities. Recombination between attenuatedmarker vaccines and field strains of BoHV-1, with thepotential emergence of virulent BoHV-1 expressing thephenotypic traits of the marker vaccines, provides another


remarkable example of virus adaptability upon evolutionin vaccinated populations. This has implications forcontrol and eradication strategies based on serologicaldifferentiation between vaccinated and infected animals.

The evolution of viral pathogens circulating in vaccinated-populations may represent a new challenge for the animalhealth sector. There is a need to better understand thedynamics of viral pathogens replicating in the field, inparticular those evolving in animal populations protectedby vaccination.

AcknowledgementsWe wish to express our gratitude to E. Domingo and F. Sobrino for their continuous support. This manuscriptwas written with support from the French Ministry ofResearch (ACI Microbiologie) and the Institut National dela Recherche Agronomique (Trans-Zoonose).


La vaccination des animaux et l’évolution des virus

K.A. Schat & E. Baranowski

RésuméSi la vaccination parvient à réduire l’incidence des maladies, il est rare qu’elleconfère une protection contre le processus infectieux, de sorte que nombred’agents pathogènes continuent à circuler au sein des populations d’animauxvaccinés. Cette circulation virale risque de favoriser l’apparition d’unerésistance aux vaccins, avec des conséquences sur l’évolution de lapathogénicité des virus et l’émergence de virus variants. Les taux élevés demutation accompagnant la multiplication des virus à acide ribonucléique (ARN)favorisent l’apparition de mutants d’échappement. Chez des bovins vaccinés,des mutations inhabituelles ont été observées au niveau du site antigéniquemajeur du virus de la fièvre aphteuse qui est également impliqué dans lareconnaissance de récepteurs. De même, des modifications atypiques ont étédétectées dans la région immunodominante du virus respiratoire syncytial bovin.Les grands virus à acide désoxyribonucléique (ADN) ont la capacité de serecombiner et de créer de nouveaux génotypes, comme c’est le cas des souchesvaccinales de l’herpèsvirus bovin de type 1 porteuses d’une délétion dans legène codant pour la glycoprotéine gE, qui présentent un risque derecombinaison avec les souches sauvages. Le virus de la maladie de Marek estsouvent cité comme exemple de la modification du pouvoir pathogène induitepar la vaccination. Les causes exactes de cette virulence accrue restent àélucider ; les auteurs examinent quelques explications possibles de cephénomène.

Mots-clésÉvolution – Maladie de Marek – Pathogénicité – Pathotype – Récepteur – Tropisme –Vaccin – Virulence – Virus.

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Vacunación de animales y evolución de los patógenos virales

K.A. Schat & E. Baranowski

ResumenPese a que reduce la incidencia de la enfermedad, la vacunación pocas vecesprotege contra la infección y muchos agentes patógenos siguen presentes enpoblaciones animales vacunadas. La circulación de agentes patógenos viralesen esas poblaciones puede favorecer el desarrollo de resistencia a las vacunas,con implicaciones para la evolución de los virus y la emergencia de variantesvirales. La elevada tasa de mutaciones durante la replicación de los virus ácidoribonucleico (ARN) favorece la emergencia de mutantes de escape. En ganadosvacunados se han observado mutaciones inusuales en el sitio antigénicoprincipal del virus de la fiebre aftosa, implicado también en el reconocimiento dereceptores. Del mismo modo, se han detectado cambios atípicos en la regióninmunodominante del virus respiratorio sincitial bovino. Los grandes virus ácidodesoxiribonucleico (ADN) pueden recombinarse, dando lugar a nuevosgenotipos, como lo muestra el potencial de las cepas vacunales del herpesvirusbovino de tipo 1 con deleción en el gen de la glicoproteína E para recombinarsecon cepas salvajes. El virus de la enfermedad de Marek suele citarse como unejemplo de cambio de patogenicidad provocado por la vacunación. Aún no sehan elucidado los motivos por los que aumenta la virulencia y los autorescontemplan las posibles explicaciones.

Palabras claveEvolución – Enfermedad de Marek– Patogenicidad – Patotipo – Receptor – Tropismo –Vacuna – Virulencia – Virus.

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Safe use of vaccines and vaccine compliance with food safety requirements

K. Grein (1), O. Papadopoulos (2) & M. Tollis (3)

(1) European Medicines Agency, 7 Westferry Circus, Canary Wharf, London, E14 4HB, United Kingdom(2) Faculty of Veterinary Medicine, Aristotle University, 54124, Thessaloniki, Greece(3) Department of Food Safety and Veterinary Public Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 0014, Rome, Italy

SummaryAdvanced technologies and regulatory regimes have contributed to theavailability of veterinary vaccines that have high quality and favourable safetyprofiles in terms of potential risks posed to the target animals, the persons whocome into contact with the vaccine, the consumers of food derived fromvaccinated animals and the environment. The authorisation process requiresthat a range of safety studies are provided to evaluate the products. The designand production of vaccines, and their safe use, are primarily assessed by usingdata gathered from extensive pre-marketing studies performed on target animalsand specific quality tests. The current post-marketing safeguards include goodmanufacturing practices, batch safety testing, inspections andpharmacovigilance. In addition to hazard identification, a full benefit/riskevaluation needs to be undertaken. The outcome of that evaluation willdetermine options for risk management and affect regulatory decisions on thesafety of the vaccine; options might, for example, include special warnings onpackage inserts and labels.

KeywordsAnimal – Assessment – Benefit – Consumer – Environment – Health –Pharmacovigilance – Risk – Safety – User – Vaccine.

IntroductionHistorically, vaccination of animals has been a strategiccomponent of policies, designed to prevent and controlinfectious diseases. In this respect, vaccination has hadevident benefits for animal welfare and health. As well asthe quality, safety and efficacy of the vaccine in relation tothe target animal, the impact on public health and theenvironment must also be considered. By improvinganimal health, veterinary vaccines can reduce thecirculation of animal pathogens and waste and may resultin a reduction in the use of disinfectants andantimicrobials.

As a matter of principle, veterinary vaccines must be safenot only for the target animal species but also for thevaccine users, consumers of foodstuffs of animal origin andthe environment. The risks associated with the use ofvaccines are primarily related to the properties of thevaccine, care in handling and administration, and recipienthost factors. Side effects may be local or systemic; they mayoccur at, or shortly after vaccination, or be delayed. Inorder to establish that a vaccine is safe, a risk assessment,followed by a benefit/risk analysis, must be undertaken foreach vaccine before it can be authorised.

Criteria and requirements for risk assessment have beendesigned to ensure that vaccine producers gather a package

of safety data on the product through studies of both targetanimals and non-target animals, as well as quality data.Extensive testing is required as part of the vaccinedevelopment in order to obtain marketing authorisation.After development, testing is also routinely performed as apart of the batch release procedure on every batch ofvaccine. New technologies have improved the safety andthe efficacy of vaccines, thus ensuring satisfactory levels ofimmunity and reducing, or even eliminating, harmfuland/or unexpected side effects in vaccinated animals.

In some cases, a risk assessment may indicate that avaccine poses a potential risk to the target animals, publichealth or the environment; if so, the benefit/risk analysis,weighing the benefits of the vaccine against its risks, willdetermine whether the vaccine can still be used. If thevaccine offers considerable advantages in preventingillness, but presents potential risks to the target animals orhuman beings or the environment, the benefits wouldneed to outweigh the risks. If the vaccine is authorised forrelease despite the risks, its use should be accompanied byadequate risk management measures that would minimiseor eliminate the risk.

Marketing authorisation depends upon the risk assessmentand benefit/risk analysis, which are based on the intendeduse and claimed benefits of a vaccine. The use and claimwill be included in the summary of product characteristics(SPC), the package insert and the labelling, which shouldprovide instructions for use, storage and waste disposal, aswell as any appropriate safety warnings. These documentsmust make clear to the user that ‘off-label’ use (use notspecified by the manufacturers) can be extremelydangerous; such off-label use could include administeringthe vaccine to non-target animal species or by a routedifferent from the recommended ones. Users should alsobe aware that the use of contaminated vaccines can causethe spread of extraneous or exotic microorganisms inspecific agent-free farms or geographical areas (10).

In recent years, and particularly in developed countries,public debate over the benefits of vaccination hasincreasingly been fuelled by fears that some risks havebeen underestimated. The suspected link betweenvaccination of cats and the development of sarcomas at theinjection site of vaccines is an example (2, 12). Some catowners are often so worried that they prefer to take the riskof not vaccinating their animals, instead of having themexposed to the potential risk of sarcoma developmentfollowing vaccination.

Another case for concern is the use of multiplesimultaneous vaccinations for different diseases, thevalidity and benefits of which are being questioned byseveral research groups. There are currently investigationsinto the possibility that such multiple vaccinations couldlead to harmful side reactions such as interference with and

overloading of the immune system of animals, particularlycompanion animals. Similarly, early life immunisationprogrammes are increasingly criticised due to theunpredictable outcome of vaccinating very young animalsand the fear of inducing tolerance or autoimmunitymechanisms (11, 15). Vaccination of animals is sometimesundertaken to mitigate the effects of poor managementsystems; this can result in serious risks of disease andshould be avoided.

In general, there is no need to establish a maximumresidue limit (MRL) for the active principles contained inspecific vaccines, and a withdrawal period is not necessaryafter vaccination in most cases, because in generalvaccination does not result in harmful residues of theactive principles or immunological responsesdistinguishable from those that arise naturally (4).However, with certain live vaccines with zoonotic agents,withdrawal periods may be necessary. Furthermore,excipients and adjuvants as primary components ofvaccines need to be considered when evaluating the safetyof vaccines (16).

The present paper will give an overview of the regulatoryrequirements for vaccines. It will also address the mainoutcomes of the risk/safety assessment of the use ofvaccines in target animal species, and in relation to vaccineusers, consumers of food derived from vaccinated animals,and the environment.

Regulatory requirementsMost countries have a range of legislation to ensure at leastminimum standards for the quality, safety and efficacy ofveterinary medicinal products. As a general rule, before aveterinary medicinal product can be sold or used, it mustbe authorised by the responsible authority of the countrywhere it will be used. This applies for pharmaceuticalveterinary medicines as well as vaccines.

In order to obtain a marketing authorisation (orregistration or licence, as appropriate) the company thatintends to bring the product on the market must submit anapplication to the authority concerned, accompanied by acomprehensive package of data on the quality, safety andefficacy of the vaccine. The application should also addressany precautionary measures to be taken when storing theveterinary medicinal product, administering it to animalsand disposing of waste, together with an indication ofpotential risks that the product might pose to human andanimal health and to the environment. Following the initialassessment of the application, additional questions usuallyarise (‘list of questions’) that the applicant (or sponsor) ofthe veterinary medicinal product will have to answer. Onceall questions have been satisfactorily addressed and it isestablished that there are no risks that would prevent the


licensing of the vaccines, a marketing authorisation will beissued, imposing specific conditions of use, storage andwaste disposal. Standards of manufacturing safety,including the design and production of vaccines, will oftenbe regulated under different legislation and separateregulating authorities (e.g. workplace safety andenvironmental safety at the manufacturing plant are notusually covered by legislation governing veterinarymedicines).

Harmonisation of rules and testing among individualcountries and regions is carried out by internationalorganisations concerned with animal health on aworldwide scale, such as the World Organisation forAnimal Health (OIE) and the World Trade Organization(WTO). There is an ongoing programme to harmonise datarequirements for veterinary medicinal products (includingvaccines) in a number of areas, e.g. quality monitoring andtarget animal safety studies, within the InternationalCooperation on Harmonisation of Technical Requirementsfor Registration of Veterinary Medicinal Products (VICH).

To give an example, in the European Union (EU) and thecountries of the European Economic Area, therequirements for obtaining a marketing authorisation arelaid down in Directive 2001/82/EC, and subsequentamendments (7). Appendix I to this Directive describes indetail the data – about the quality, safety and efficacy of theproduct – that must be provided with an application for amarketing authorisation. Directive 2001/82/EC, asamended, also requires the applicant to provide – inaddition to the data on quality, safety and efficacy –information on the test methods and any precautionarymeasures to be taken when storing the veterinary medicinalproduct, administering it to animals and disposing ofwaste, together with an indication of potential risks that theproduct might pose to human and animal health and to theenvironment. Further guidance is given in specificguidelines issued by the Committee for Medicinal Productsfor Veterinary Use (CVMP) of the European MedicinesAgency (EMEA) (6) and the European Commission (3). Forvaccines which are the subject of a EuropeanPharmacopoeia monograph, specific requirements may beincluded in the relevant monograph (9).

All data are assessed by the responsible authority, and arisk assessment and a benefit/risk analysis are carried outbefore a decision on the marketing authorisation is taken.Different procedures exist in the EU to obtain a marketingauthorisation: in the centralised procedure, which isoptional for new chemical entities and innovativeproducts, and mandatory for products derived bybiotechnological processes, the application is assessed bythe CVMP. This procedure leads to a marketingauthorisation binding in all EU Member States. In themutual recognition procedure and the decentralisedprocedure the Member States, in which the product is

intended to be marketed, carry out the assessment aimingfor consistent marketing authorisations. Nationalmarketing authorisations issued by individual MemberStates exist for veterinary medicinal products, which wereon the market in the EU before 1995, and can be issuedtoday, if a product is intended for one single EU MemberState only. Depending on the process of the marketingauthorisation chosen, the procedure is defined byRegulation (EC) No. 726/2004 (8) or described inDirective 2001/82/EC (7).

Principles of riskassessment/risk analysisIn order to ensure the safety of vaccines a risk assessmentis necessary. The aim of the risk assessment is to identifyhazards, to estimate the likelihood that the hazards willlead to actual harm, and to take decisions aboutappropriate measures for prevention and control. Riskassessment is a science-based process involving thefollowing stages:

– hazard identification

– hazard characterisation

– exposure assessment

– risk characterisation.

In the first steps the potential hazards associated with thevaccine are comprehensively identified and characterised.In parallell, the exposure scenarios for the differentprotection goals for the vaccine under consideration areidentified and described. A risk characterisation thenestimates the probability of the identified hazardsoccurring. If any risks are not as low as reasonablypracticable, the process of risk assessment should berepeated to ascertain whether additional managementtechniques and risk mitigation measures could reduce thelevel of risk.

Although, wherever possible, the risk assessment shouldbe based on quantifiable outcomes, it is recognised thatmany of the judgments must necessarily be qualitativeonly. The risk can often be judged on a rating scale rangingfrom negligible through low and medium to severe orunacceptable.

Once all risks have been assessed – and if possible reduced– the residual risks are weighed against the benefits of thevaccine, in order to decide whether to grant a marketingauthorisation, and to consider possible risk mitigationmeasures, if appropriate. The approved conditions of useof a veterinary medicinal product should be described in aclear and unambiguous manner. The identified risks andrisk mitigation measures must be communicated to theusers of the vaccines.


Safety of the target animals Problem statementErrors in the manufacturing process or incorrect use ofvaccines are the two main causes of potential risks fortarget animal species. Unsafe live or poorly inactivatedvaccines may harm the animal to which they areadministered, and the causative agent may also spread andharm other animals or have serious ecological effects.Apart from the threat of potentially serious consequencesrelated to contamination of vaccines by extraneous agents,which in extreme cases could lead to disease outbreaks anddeath of animals (10, 17), it is the likelihood of localtoxicity and long-lasting side effects that generates thegreatest concern for animal health and welfare (13).Adverse events can vary from carcass damage, as in thecase of particularly aggressive adjuvants, to death ofanimals.

Scope of the assessmentThe purpose of the evaluation during the developmentphase is to determine whether the vaccine is safe if used atthe proposed dose level. The evaluation is limited to thehealth and welfare of the target animals.

Safety testing in target animal species must show thepotential risks that may occur under the proposedconditions of use of vaccines. Laboratory safety studieshave been designed to meet necessary basic requirementsbefore initiating field trials. For the final assessment, safetydata produced under controlled experimental conditionswill be supported by results obtained during field trials.These trials are carried out with a statistically significantnumber of animals and designed to reflect, as accurately aspossible, the practical conditions of use of the productsbeing tested.

Risk assessment

Hazard identification and characterisation

The specific information that needs to be provideddepends upon various factors, including:

– the type of vaccine (inactivated or live, bacterial or viral)

– the nature of the adjuvants that will be used

– the use history of similar products

– dose

– claims

– proposed usage regimen

– animal species, class and breed.

As a general rule, the ‘worst case’ or most severe potentialharm should be assessed, even if it is highly unlikely (e.g.

a once in a lifetime probability), using a dosecorresponding to the quantity of the product to berecommended and of the maximum titre or potency.

One dose, repeated doses and overdose tests are normallyrequired for each of the target species, testing animals ofthe most sensitive class, age and sex identified on the label,and using all recommended routes and methods ofadministration. Essential parameters to be evaluated forthe safety of a vaccine are local and systemic reactions tovaccination, including application site reactions and theirresolution, and clinical observation of the animals. Otherobjective criteria, such as rectal temperature andperformance measurements, are also recorded.Examination of the reproductive performance of breedinganimals as well as of immunological functions must beconsidered when data suggest that the initial material fromwhich the product is derived may be a risk factor.

For live vaccines specific additional tests are required, e.g.testing the potential that different levels of pathogenicitymay be retained in the case of specific animal species, or ofa certain age or class of animal, or specific routes ofadministration (induction of clinical signs or lesions ofdisease, or persistency/latency of the microorganism in thebody of a vaccinated animal). Special requirements for livevaccines include the definition of the biologicalcharacteristics of the vaccine strain (e.g. animal tissuetropism) and the exclusion of any potential for the vaccinestrains to revert to virulence.

The nature and severity of adverse reactions following theadministration of a veterinary vaccine can be dependenteither on the antigen that is used (e.g. crude bacterialantigen compared to well-purified viral antigens) or on thesusceptibility of the different animal species. The depth,length and width of local reaction as well as anyhistological change in the tissue structure have to bemeasured. Local reactions can vary from granulomas oflimited or larger extent, to abscesses; from inflammation tonecrosis and fibrosis of tissues. In recent years, someexcipients (e.g. as part of stabilisers) or adjuvants(particularly oil/emulsion adjuvants) and vaccineadministration (in terms of both route and timing) havefrequently been implicated as the cause of adversereactions, both at injection sites and systemic (includingfever, arthritis, anorexia, soreness and lethargy). Moreover,recent reports have raised concerns among professionals inrelation to vaccination and delayed adverse events,particularly in companion animals and specifically inrelation to vaccine-associated fibrosarcomas in cats andimmune-mediated disease in dogs. Although their role isstill debated, adjuvants have been associated with a localtissue irritation which in very extreme circumstances may result in metaplasia of fibrocytes and tumourformation (14).


Most of the common systemic reactions – such as pain,fever and anorexia, but also vomiting, reduction in milkyield, anaemia, arthritis, epilepsy, thyroid disease, liverfailure, diabetes and allergies – have been associated withthe use of vaccines in animals. Residual endotoxins andpyrogenic effects of antigens and adjuvants (oil, saponin)may be responsible for adverse events which can morecommonly be expected as a consequence of the use ofvaccines. Anaphylactic and delayed allergic reactions canalso occur but are more insidious and in most cases are not controllable. The risk of allergic reactions has beenreported to increase after repeated injection of vaccines(13). Other risks may be posed by the immunosuppressiveeffects of modified live viruses, such as bovine herpesvirus 1 (BHV-1), bovine viral diarrhoea virus(BVDV), and the SG33 strain of myxomatosis virus used inspecific vaccines. Parvovirus and canine distempervaccines have been reported to be responsible for manydiseases of the immune system in dogs (1, 15). Among the most deleterious and suspected effects on theimmune system are tolerance and autoimmunity,overloading of the immune system by multiple and simultaneous administration of vaccines, interactionwith other vaccines or reciprocal interference with theimmune response against antigens.

Exposure assessment

In principle, adverse events may potentially occur at anyexposure level to vaccines, whether administered once in alifetime or repeatedly, and with products containingminimum or larger combinations of antigens. In particular,risks may increase when vaccines are administered topregnant or lactating animals, or are used for early lifeimmunisation of animals, such as in ovo or day-oldvaccination of birds. Concern has been expressed about this; some practitioners argue that the youngest recommended age for vaccinating various speciesshould be increased, because early vaccination may interfere with persistent maternally derivedantibodies, and may therefore affect both the safety andefficacy of vaccination. It is necessary to ensure a widespectrum of protection against major infectious diseasesearly in the life of animals; consequently, in most casesanimals have to be vaccinated repeatedly in a relativelyshort time period, which increases the risks of adversereactions. In order to avoid unnecessary vaccination ofanimals, data generated by studies on the duration ofimmunity should be used when preparing vaccinationschemes.

Risk characterisation

Once hazards have been identified as likely, the risksassociated with those hazards should be characterised in

terms of the harm they might cause. Two broad categorieswith qualitatively different risk profiles are commonlyrecognised. Inactivated and subunit vaccines, as well asconventionally designed and produced live vaccines, aregenerally considered to be low-risk products in respect totarget animal safety. Live genetically modified organisms(GMO) or vectored vaccines are usually considered to havehigh-risk profiles. In order to balance the greater risks ofsuch GMO or vectored vaccines, higher levels of efficacyand benefits are normally required from them than fromconventional vaccines. Nevertheless, even low-riskproducts may entail higher risks for the target animals, e.g.if injected intramuscularly.

Risk management and risk communication

Improved manufacturing processes (e.g. targeted use ofonly protective epitopes from specific proteins, or reduceduse of sensitising agents such as residues of bovine serum,cell debris, egg proteins, preservatives) and new generationadjuvants are key issues for the prevention of side effects intarget animal species. In particular, adjuvants may be tailored for specific needs of the antigen or species andto enhance the type (e.g. humoral, mucosal, cell-mediated), timing and magnitude of protectiveimmunoresponse. The use of routes and methods ofadministration known to cause less adverse reactionsshould be preferred. Vaccination schemes should be developed taking into account which vaccines are moreappropriate for animals of different ages and categories,and provide long-lasting immunity following a single immunisation, thus reducing the risks of potentialimmunosuppression or immunomediated diseases.

Recommendations for the appropriate use of ‘core’ vaccinesin companion animals should be based on the severity ofdisease caused by the agent, the risk of the agent beingtransmitted to susceptible animals, and the potential for aparticular infection to be zoonotic. Antibody titre testingbefore vaccination could be useful to determine if avaccination is really needed. ‘Non-core’ vaccines should beused when a known or likely risk of exposure isanticipated or when an individual animal’s lifestylerepresents a significant risk of infection. Warnings aboutpossible side effects should realistically reflect the dataobtained in safety studies. The outcome of the riskassessment must be summarised within the characteristicsof each product, and the label should include warningsabout potential over-dosage, contra-indications, andundesirable side effects for each target species and categoryof animal (e.g. pregnant or lactating animals). If theproduct is incompatible with other vaccines or medicinesthat might be administered, that must also be reported, asmust any special precautions for use. In the case of anyidentified risk, appropriate warnings must be incorporatedin the package insert and/or label.


User safetyProblem statementVaccines should be safe not only for the target species, butalso for the user, i.e. the person administering the vaccineor any other person assisting or involved in theadministration of the vaccine or likely to come into contactwith it.

The user must be informed of any specific hazard throughthe label and the package insert. This warning mustidentify any risk, and give advice on ways to prevent itoccurring, as well as the measures to be taken in the caseof exposure. The hazard could occur during normal use orthrough an accidental exposure during or following theadministration.

It is evident that user safety is a critical factor for vaccinescontaining well-known live zoonotic agents or certainadjuvants. However, for the majority of vaccines thesituation is not so clear. Risk assessments need to beperformed, considering the specific properties of vaccinesand their intended use on a case-by-case basis.

Scope of the assessmentAn assessment of the user safety of a product addressesonly situations resulting from the normal conditions of useand from foreseeable accidents (including accidental self-injection, oral ingestion or inhalation). It does not considerexposure resulting from deliberate misuse.

For the assessment, the user is regarded as any personwho:

– administers the vaccine

– comes into contact with the vaccine or componentsbefore its application to the animal (e.g. during storage orpreparation of the product to be administered)

– comes into contact during its application

– may be exposed to the vaccine after its application (e.g.through contact with disposed of, unused or wasteproduct, or with treated animals).

This implies that the user can be, for example, aveterinarian, a farmer, a breeder, a pet-owner or any personwho assists in restraining an animal during vaccination orwho lives in the same environment. Consumers ofproducts derived from vaccinated food-producing animals(such as meat and milk) are excluded from this definition(see ‘Consumer safety’). This discussion does not coveroccupational safety during the manufacturing of vaccinesor other risks, for example, due to injury from amechanical vaccination device or from a contaminatedneedle.

Risk assessment


Risk assessment is primarily concerned with examining theeffects of the active ingredients, but also, if necessary, ofexcipients and, especially, adjuvants. For live vaccines thehuman pathogenicity of the vaccine strain is the mainconcern. For certain vaccine strains, pathogenicity hasbeen documented by study of human cases caused by thesame strain (e.g. Brucella melitensis Rev.1). The probablepathogenicity of a strain could also be assessed frompublished information for related modified strains or fieldstrains (e.g. rabies) or from pharmacovigilance data.Agents that are rarely pathogenic for humans may be of special interest in the case of immunocompromisedindividuals or pregnant women (e.g. toxoplasma). For inactivated, but also for some live vaccines, effects ofadjuvants, such as local or systemic reactions as a result of accidental injection, are of most concern (e.g. oiladjuvants).

Exposure assessment

Factors to consider include:

– the method of preparation of a vaccine (e.g. recoveryfrom liquid nitrogen, rehydration, dilution of ingredients,loading in application apparatus or system)

– the route of administration of the vaccine (e.g. injectionby syringe or mechanical device, coarse spray, oral)

– the duration and frequency of exposure to the vaccine

– the number, species and category of animals to bevaccinated (e.g. individual or mass vaccination,companion or food-producing animals)

– the time period of excretion from vaccinated animals.

The risk of exposure to the vaccine is shared equallybetween both the person who administers the vaccine andpeople who assist in restraining the animal(s). In caseswhere the vaccine strain is excreted by the vaccinatedanimal(s), the animal owners or caretakers may in additionbe exposed to the strain after vaccination.


In contrast to pharmaceuticals, where information ondose–response relationships is available, in vaccines noquantitative risk assessment can be made. As an example,if hazards are identified for live vaccines, it must beassumed that the effects will occur at any exposure level.


Recommendations for managing risk includeimplementing appropriate precautionary measures such as


the use of personal protective equipment. When thevaccine strain may be excreted, the period during whichthis is liable to occur should be stated on the packageinsert or label. In some cases, recommendations forappropriate action will be linked with particularcharacteristics of the user, such as immunocompromisedpersons and pregnant women. Guidance on remedialaction to be taken following accidental contact is also givenwhen necessary. If the advice of a physician is considerednecessary, adequate information should be given on thenature of the identified risk, taking into account that it isnot always possible for the physician in an emergencysituation to identify the risk and take the full responsibilityfor risk assessment without proper information.Statements such as ‘seek medical advice immediately andshow the package insert or the label to the physician’should be included only when a specific risk has beenidentified. When the assessment does not identify anyspecific risk, an appropriate statement could be includedon a case-by-case basis (e.g. ‘none’, ‘no specific riskidentified’).

Guidance on standard warnings to be used in the EU hasbeen published (3). A typical example is the followingwarning for vaccines containing oil adjuvants: To the user:‘This product contains mineral oil. Accidental injection/selfinjection may result in severe pain and swelling,particularly if injected into a joint or finger, and in rarecases could result in the loss of the affected finger if promptmedical attention is not given. If you are accidentallyinjected with this product, seek prompt medical adviceeven if only a very small amount is injected and take thepackage insert with you. If pain persists for more than 12hours after medical examination, seek medical adviceagain.’ To the physician: ‘This product contains mineral oil.Even if small amounts have been injected, accidentalinjection with this product can cause intense swelling,which may, for example, result in ischaemic necrosis andeven in a loss of a digit. Expert and prompt surgicalattention is required and may necessitate early incision andirrigation of the injected area, especially when there isinvolvement of finger pulp or tendon.’

Consumer safety Problem statementThe use of a veterinary medicinal product in food-producing animals may result in the presence of residuesof the medicine in the animal body and in animal-derivedfoodstuffs such as meat, milk and eggs. This applies topharmaceutical veterinary medicines as well as toimmunological products. While medicinally inducedimmunological responses are usually indistinguishable

from those which arise naturally, and are considered not toaffect consumers, consideration must be given to othersubstances contained in the vaccine, in particularexcipients and adjuvants.

Scope of the assessmentThe purpose of the assessment is to evaluate the known or potential adverse effects on human health of exposure to food-borne hazards or, more specifically, of exposure toresidues of the chemical components of the immunologicalveterinary medicinal products used in food-producinganimals. In the EU, such a safety-of-residue evaluation isrequired for all pharmacologically active substances whichremain in foodstuffs obtained from animals to which theveterinary medicinal product in question has beenadministered. Active principles of biological origin used inan immunological veterinary medicinal product intendedto produce active or passive immunity or to diagnose astate of immunity are excluded.

In the EU the risk assessment of any chemical componentsof vaccines that may affect consumer safety is considered ina separate procedure prior to the marketing authorisationprocess. Council Regulation (EEC) 2377/90 lays down theprocedure and lists all substances that are allowed to beused in veterinary medicinal products for food-producinganimals. Appendix I lists all substances for which finalMRLs have been established, Appendix II lists allsubstances for which the specification of MRLs was notconsidered necessary to protect consumer health, andAppendix III contains all substances with provisionalMRLs (5).

Adjuvants in vaccines, due to their very nature, are usuallypharmacologically active and require a safety-of-residueevaluation. Depending on the nature of the excipient, thesemay be exempted following a case-by-case considerationbased on appropriate data that has shown the absence ofsuch activity at the dose at which the adjuvant is includedin the veterinary medicinal product.

Substances used in the manufacturing process of the activeingredients, which are not intended to be present in thefinal product but of which traces might be present, are notconsidered to require a safety-of-residue assessment.

As mentioned before, medicinally induced immunologicalresponses are usually indistinguishable from those whicharise naturally, and are considered not to affect consumers.However, on a case-by-case basis, depending on the natureof the vaccine, e.g. in the case of live vaccines containingzoonotic organisms, a precautionary withdrawal periodwill be required to exclude risks to the consumer of foodderived from the vaccinated animal.


Risk assessment


The purpose of hazard identification is to identify residuesof a vaccine that may cause adverse effects on health andthat may be present in any particular food derived fromanimals. In the hazard characterisation stage, the nature ofthe adverse effects associated with these residues isevaluated qualitatively and/or quantitatively on the basis oftoxicological and pharmacological studies in laboratoryanimal species. Where available, observations in humansare taken into account. At this stage, where appropriate,the acceptable daily intake (ADI) for the substance underconsideration is established.

Exposure assessment

The exposure assessment concerns vaccines intended foruse in food-producing animals, and evaluates the likelyintake of residues of a vaccine through food of animalorigin. Data on absorption, pharmacokinetics, metabolismand residue depletion are usually necessary for theexposure assessment.


In a risk characterisation, an estimate is made of the risksto the consumer from any residues from vaccines that maybe present in animal products. Regarding the chemicalcomponents identified as potential hazards for theconsumer, the risk characterisation will decide whetherMRLs would need to be established. Consideration is givento whether a withdrawal period would be necessary beforefood can be derived from the vaccinated animal.


The outcome of the assessment of risks to the consumershould be summarised and, where any risk is identified,appropriate advice should be given on mitigationmeasures. Such measures, e.g. a withdrawal period, shouldbe incorporated in the SPC, package insert and label.

Environmental safetyProblem statementA veterinary medicinal product may have undesirableeffects on the environment and therefore, before anyveterinary medicinal product can be authorised, any risk ofharm it may pose to the environment should be assessed.On the basis of the assessment, specific risk mitigationmeasures may be considered.

Scope of the assessmentIn the EU the environmental assessment is undertaken intwo phases. Phase I is compulsory and should indicate the

potential exposure of the environment to the product, andthe level of risk associated with any such exposure. Whereit is concluded that the risk is low, there will generally beno need to proceed to Phase II and no furtherinvestigations will be required. In the majority of cases, thenature of vaccines is such that they will have a very lowenvironmental risk potential. It can be expected that aPhase II assessment will be necessary only in exceptionalcircumstances, e.g. in vaccines containing live GMOs (3).

The level of detail to be considered in a risk assessment willdepend on the characteristics of the vaccine. Little detailwill be required, for example, where it is immediatelyobvious that the hazards and hence the consequent risksare low, or that the proposed control measures are clearlyadequate to limit contact between the product and theenvironment. For example, for inactivated vaccines to beadministered by injection, the hazards and risks from theactive ingredients are likely to be negligible.

Risk assessment


In the context of the environmental risk assessment forvaccines, hazards are defined as those features of thesubstance which have the potential to cause harm to theenvironment either directly (as in the case of infection of anon-target-species by a vaccine virus) or through someform of possible event (such as infection by organismsexcreted by the vaccinated animal). It is important to beexhaustive in the identification of possible hazards, whichshould aim to identify all possible factors contributing toadverse effects and should include the following:

– the capacity of live organisms to transmit to non-targetspecies

– the shedding of live vaccine organisms from vaccinatedanimals (route, numbers, duration)

– the capacity to survive, establish and disseminate

– pathogenicity to other organisms

– potential for other effects of live product organisms

– the toxic effects of the product components

– the toxic effects of excreted metabolites.

Regarding the two latter effects, in the case of productswhich are administered by injection, no detailedassessment of the potential risk of the excipients is likely tobe required when the substances are of biological origin orform part of the animal’s normal diet.

Exposure assessment

In the first step, the likelihood (probability and frequency)of the hazard(s) is estimated. A key factor in determining


this is the potential receiving environment. This includesthe wider as well as the local environment in which theproduct is intended or likely to be used.

Particular characteristics of the local environment thatcould contribute to the likelihood of the hazard – e.g.climatic, geographical and soil conditions, demographicconsiderations, the types of fauna and flora in the potentialreceiving environment – should be identified and assessed.Consideration should be given to any potential exposure ofthe environment to the product and the magnitude andduration of such exposure. The exposure assessmentshould consider:

– the type of packaging and procedures before and afteradministration

– the route of administration (parenteral vs. oral vs.oculonasal vs. spray)

– shedding of live product organisms (route, numbers,duration).

For the ‘hazard-survival capacity’ of living organisms, it isappropriate to assess the proportion of the organisms thatare likely to survive. If the organism has pathogeniccharacteristics, the proportion of target species in theenvironment likely to be affected should be assessed,taking into consideration the likelihood that the organismwill spread to or reach these species. It is recommendedthat the possibility of exposure and the likelihood ofhazards occurring are expressed as ‘high’, ‘medium’, ‘low’or ‘negligible’, although it is recognised that this requiressubjective judgment.

Subsequently the consequences of possible hazards areassessed. This must be done for each identified hazard ofthe product being assessed. Whenever it is possible orprobable that the components in the product will reach theenvironment, it must be considered whether thatenvironment would cause or allow the hazard to happen.Thus, again, the characteristics of the potential receivingenvironment need to be considered.

For vaccinal organisms or excreted passage organisms, themain consideration will be the likely presence or absenceof susceptible non-target species in the potentially affectedenvironment.


Having identified any hazards and assessed the degree andlikelihood of exposure and the consequences of thatexposure, it is necessary to evaluate the risk associatedwith each hazard. Risk is generally held to be the productof exposure/likelihood and consequence. It is inevitablygoing to be difficult to ‘multiply’ qualitative statementssuch as ‘high’ and ‘low’, but Table I should help thisprocess. The risk matrix is not definitive and there willalways be some scope for flexible, case-by-case evaluation.In many cases, it will be necessary to decide between oneof two outcomes and, as in the earlier parts of the process,some justification for the choice should be provided. Inaddition, a range of risks may be apparent if more than onehazard is being evaluated. There will therefore be a need tomake an overall assessment of the risk, taking all factorsinto consideration. Once an overall assessment of the riskassociated with each hazard has been produced, it will benecessary to evaluate the significance of the risk.


If the environmental risks are not as low as reasonablypracticable, the process of risk assessment in relation to thehazard should be repeated to ascertain whether the use ofadditional management techniques could reduce the levelof risk; consideration might be given, for example, tolimiting the proposed routes of administration to thoselikely to lead to a lower level of risk. If it is considered thatthere is insufficient knowledge to come to a satisfactoryconclusion, other studies and a Phase II assessment shouldbe undertaken, addressing the specific issues that give riseto concern on a case-by-case basis.

The outcome of the environmental risk assessment shouldbe summarised and, where any risk is identified,appropriate warnings and advice on mitigation measures


Table IEnvironmental risk assessment: characterising the nature of a risk (high, medium, low, zero) by evaluating the likelihood of itsoccurrence and the severity of its consequences

High likelihood Moderate likelihood Low likelihood of Negligible likelihoodof hazard occurring of hazard occurring hazard occurring of hazard occurring

Severe consequences High High Medium Effectively zero

Moderate consequences High High Medium/low Effectively zero

Minor consequences Medium/low Low Low Effectively zero

Negligible consequences Effectively zero Effectively zero Effectively zero Effectively Zero

should be incorporated in the SPC, package insert andlabel.

PharmacovigilanceVeterinary pharmacovigilance monitors the safety ofveterinary medicines, including vaccines, used for theprophylaxis, diagnosis or treatment of disease in animalsonce they have reached the market after authorisation. Theaim is to ensure that veterinary medicines are safe for theanimals, for persons who come into contact withveterinary medicines, for the environment and, in the caseof medicines used in food-producing animals, forconsumers of the food derived from these animals.

Under the EU pharmacovigilance scheme, suspectedadverse reactions in animals and in human beings relatingto the use of veterinary medicinal products under normalconditions are recorded. The EU system also takes intoaccount any available information related to:

– lack of expected efficacy

– off-label use

– investigations into the validity of the withdrawal period

– potential environmental problems arising from the useof the product, which may have an impact on thebenefit/risk balance of the product.

The responsibility for pharmacovigilance reporting lieswith the marketing authorisation holders, who arerequired to collect and evaluate all reports of suspectedadverse reactions to their veterinary medicinal products,and report to the responsible authority for the veterinarymedicinal product concerned. The adverse reaction reportsare submitted mainly by veterinarians, but also by animalowners. All suspected serious adverse reactions and humanadverse reactions relating to the use of the veterinarymedicinal product must be reported promptly by thecompany, usually within 15 or 30 days after it receives thereport (e.g. 15 days for the EU), depending on the specificlegislation of the country where the product is authorised.All adverse reports received, serious and non-serious, mustbe compiled in a so-called Periodic Safety Update Report(PSUR) or Periodic Summary Update (PSU), whichincludes a benefit/risk analysis of the product. The PSURor PSU is to be submitted to the responsible authority atspecified intervals. In the light of any adverse reportsreceived, the benefit/risk analysis of the product isreviewed. If necessary, the conditions for the authorisationmay be amended, e.g. by amending the claim or by addingnew or revised warnings to the SPC, package insert andlabel. If the risks identified through pharmacovigilancecannot be overcome by risk management measures and therisk/benefit balance is no longer positive, the marketingauthorisation of the product may even be suspended orwithdrawn.


Utilisation sans risques de la vaccination et conformité desvaccins avec les exigences de la sécurité sanitaire des aliments

K. Grein, O. Papadopoulos & M. Tollis

RésuméGrâce aux évolutions technologiques et réglementaires, les vaccins vétérinairesactuellement disponibles sont de grande qualité et présentent un profil desécurité favorable en termes de risques potentiels pour les espèces cibles, pourles personnes qui manipulent les vaccins, pour les consommateurs de produitsalimentaires issus d’animaux vaccinés et pour l’environnement. Le processusd’autorisation exige qu’une série d’études soient réalisées afin d’évaluerl’innocuité des produits. L’évaluation des vaccins au stade du développement, dela production et de l’utilisation sans risque se fait principalement au moyen


Utilización segura de vacunas y observancia de las normas sobre higiene de los alimentos en el uso de vacunas

K. Grein, O. Papadopoulos & M. Tollis

ResumenLos adelantos tecnológicos y los regímenes reglamentarios han ayudado adisponer de vacunas veterinarias que aúnan gran calidad y características deseguridad favorables desde el punto de vista de los posibles riesgos quepresentan para los animales diana, las personas que entren en contacto con lavacuna, los consumidores de alimentos procedentes de animales vacunados yel medio ambiente. El proceso de autorización requiere que se presentendiversos estudios de seguridad para evaluar cada producto. Al evaluar laconcepción y fabricación de vacunas y determinar el grado de seguridad queofrece su empleo, se utilizan sobre todo datos procedentes de vastos estudioscon animales diana, previos a la comercialización, y de controles de calidadespecíficos. Una vez que un producto ha obtenido licencia de comercializacióntambién existen medidas de salvaguardia, que hoy en día consisten en aplicarbuenas prácticas de fabricación y pruebas de seguridad de los lotes, realizarinspecciones e instaurar un dispositivo de farmacovigilancia. Además dedeterminar los peligros, es necesario proceder a una evaluación completa de larelación entre beneficios y riesgos. Los resultados de tal evaluacióndeterminarán la línea que se adopte en cuanto a la gestión de riesgos e influiránen las decisiones normativas sobre el grado de seguridad que ofrece la vacuna.Cabría obligar al fabricante, por ejemplo, a incorporar un aviso especial en lasetiquetas o encartes al embalar el producto.

Palabras claveAnimal – Beneficio – Consumidor – Evaluación – Farmacovigilancia – Medio ambiente –Riesgo – Salud – Seguridad – Usuario – Vacuna.

d’études approfondies conduites avant la commercialisation chez les espècescibles, ainsi que de tests de qualité spécifiques. Les garanties postérieures à lacommercialisation sont fournies par les bonnes pratiques de fabrication, par lesessais de sécurité par lots, par les inspections et par la pharmacovigilance.Après avoir identifié les dangers, une évaluation exhaustive du rapportbénéfice/risque doit être réalisée. Les résultats de l’évaluation mettent en avantcertaines options de gestion du risque et déterminent les mesuresréglementaires à prendre en matière de sécurité ; par exemple, des mises engarde spéciales pourront être exigées sur les emballages et les étiquettes desproduits.

Mots-clésAnimal – Bénéfice – Consommateur – Environnement – Évaluation – Pharmacovigilance– Risque – Santé – Sécurité – Utilisateur – Vaccin.

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Bennett D. (2004). – Type I immune-mediated polyarthritisin dogs: 39 cases (1997-2002). J. Am. vet. med. Assoc., 224 (8), 1323-1327.

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4. European Commission (2005). – EudraLex: Volume 8 –Notice to Applicants and Note for Guidance. Establishmentof maximum residue limits (MRLs) for residues of veterinarymedicinal products in foodstuffs of animal origin. Availableat: http://ec.europa.eu/enterprise/pharmaceuticals/eudralex/homev8.htm (accessed on 4 July 2007).

5. European Council (1990). – Council Regulation (EEC) No.2377/90 of 26 June 1990 laying down a Communityprocedure for the establishment of maximum residue limitsfor veterinary medicinal products in foodstuffs of animalorigin Off. J. Eur. Communities, L 224, 1-8.

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17. Téllez S., Casimiro R., Vela A.I., Fernández-Garayzábal J.F.,Ezquerra R., Latre M.V., Briones V., Goyache J., Bullido R.,Arboix M. & Domínguez L. (2006). – Unexpectedinefficiency of the European Pharmacopoeia sterility test fordetecting contamination in clostridial vaccines. Vaccine, 24 (18), 1710-1715.



Marker vaccines and the impact of their

use on diagnosis and prophylactic measures

P. Vannier (1), I. Capua (2), M.F. Le Potier (1), D.K.J. Mackay (3)*, B. Muylkens (4)**, S. Parida (5), D.J. Paton (5) & E. Thiry (4)

(1) Agence française de sécurité sanitaire des aliments (AFSSA), BP 53, 22440 Ploufragan, France

(2) Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padua, Italy

(3) European Medicines Agency (EMEA), London, E14 4HB, United Kingdom

(4) Virology, Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of

Liège, B-4000 Liège, Belgium

(5) Institute for Animal Health, Pirbright, GU24 0NF, United Kingdom

After the first author, who coordinated the composition, the authors’ names are listed in alphabetical order.

The different authors wrote on the following topics: I. Capua on avian influenza; S. Parida, D.J. Paton and

D. Mackay on foot and mouth disease; M.F. Le Potier on classical swine fever; B. Muylkens and E. Thiry

on infectious bovine rhinotracheitis and P. Vannier on Aujeszky’s disease

* The views expressed in this article are the personal views of the author and should not be taken

to represent the position of the EMEA, the Committee for Medicinal Products for Veterinary Use or

the European Commission

** Research fellow at the Fonds de la Recherche Scientifique – FNRS in Belgium

Summary

Molecular biology and technical advances in DNA recombination have ushered

in a new era in vaccinology. This article examines the recent development of

specific marker vaccines and examines the impact of their use on the diagnosis

and prevention of major infectious diseases. Gene-deleted vaccines, DIVA

strategies (differentiating infected from vaccinated animals) and similar methods

have been successfully applied in the control and eradication of Aujeszky’s

disease, infectious bovine rhinotracheitis, classical swine fever, foot and mouth

disease and, recently, avian influenza. The efficacy and performance of existing

marker vaccines and their companion diagnostic tools (which should be assesed

by an independent body) are discussed, as are the ways in which these tools are

deployed by competent authorities. The limits and the advantages of the use of

marker vaccines are carefully analysed in the light of practical experiences.

Although these vaccines can limit the speed and the extent of virus

dissemination and thus reduce the number of animals slaughtered, marker

vaccines are no substitute for sanitary measures. Early detection and warning

systems and the quick implementation of sanitary measures, including stamping

out, remain key issues in the control of highly contagious diseases.

Keywords

Aujeszky’s disease – Avian influenza – Classical swine fever – Companion diagnostic tool

– Control – DIVA (Differentiating infected from vaccinated animals) strategy –

Eradication – Foot and mouth disease – Latent infection – Marker vaccine – Sanitary

measure – Vaccination – Viral excretion – Virus carrier state.

IntroductionMolecular biology and technological advances indeoxyribonucleic acid (DNA) recombination have usheredin a new era in vaccinology. In particular, ‘deleted’vaccines, used in conjunction with an appropriatediagnostic kit, have emerged over the past ten years,enabling infection-specific antibodies to be recognisedregardless of an animal’s vaccination status. The first suchvaccines were used to protect pigs against Aujeszky’sdisease (AD). The same principles were subsequentlyapplied to the development of vaccines against infectiousbovine rhinotracheitis (IBR). For classical swine fever(CSF), subunit proteins were obtained from baculovirusrecombinant and the resulting vaccine obtained aEuropean marketing authorisation, re-launching thedebate on whether or not to use sanitary measures ormedical prophylactic treatments. The same principle is alsoat work when the detection of antibodies to non-structuralproteins (NSP) is used to identify animals infected withfoot and mouth disease virus (FMDV), whether or not theyhave also been vaccinated. Furthermore, more recently,recombinant vaccines have been used to protect birdsagainst avian influenza (AI).

An historic example: marker vaccines used againstAujeszky’s diseaseAujeszky’s disease virus (ADV) belongs to the subfamilyAlphaherpesviridae of the family Herpesviridae, which infectthe central nervous system and other organs (such as therespiratory tract) in virtually all mammals, except humansand the tailless apes. It is associated primarily with pigs,the natural host, which remain latently infected followingclinical recovery. After primary infection, most pigsdevelop clinical signs, depending on their age. In naïvepiglets, nervous signs are observed and the mortality canbe very high. In sows, reproductive disorders are inducedafter infection. In fattening pigs, general clinical signs, suchas fever and loss of appetite associated with respiratorydisorders of varying severity, are observed. Silent infectioncan also occur.

Currently available Aujeszky’s disease marker vaccines

Advances in molecular biology have contributed to betterknowledge of the genome of existing vaccine strains. Bystudying conventional vaccine strains, it was found thatcertain coding sequences of the single-sequence shortsection of the Bartha strain of the ADV had been deleted.

These sequences, situated in enzymatic restrictionfragment BamHI no. 7, code for two structuralglycoproteins: gE and gI. Accordingly, the Bartha strain,when isolated under natural conditions, does not expressgE, which makes it possible to distinguish vaccinated pigsfrom infected pigs, provided, of course, that thecorresponding enzyme-linked immunosorbent assay(ELISA) kits are used. ELISA kits make it possible to detectanti-gE antibodies in the serum of pigs, by usingmonoclonal antibodies that are very specific to certainantigenic determinants of gE, as described by van Oirschotet al. (129, 131).

Subsequently, knowledge about the molecular biology ofmutants of the ADV led to a better understanding of thefunctions of the viral glycoproteins. The first factor ofvirulence that was identified in the herpes virus was thethymidine-kinase enzyme, which allows the virus toreplicate itself in the central nervous system. Later, thevirulence of strains of the ADV not expressing theglycoprotein membrane gE was seen to have diminishedconsiderably compared with that of field viruses (9). ThisgE would therefore appear to play a major role in thespread of the virus within the nervous system, with theinfection spreading both through the olfactory tract andtrigeminal cavity (82). This knowledge has made itpossible to develop new vaccines by means of geneticrecombination, which modifies the genome of the vaccinestrains in order to excise, remove or delete certainsequences that code for glycoproteins and prevents theirexpression. These proteins do not induce antibodies invaccinated animals and so are used as serological markersfor infection by wild-type viruses. The functions of thesesame proteins are often partially responsible for thevirulence of field strains (such as gE); their non-expressionhelps to reduce or eliminate the pathogenicity of thesevaccine strains, which always express the majorglycoproteins (gB, gC, gD), thus inducing protectiveimmune responses in vaccinated or infected pigs.

Another generation of vaccines, not yet on the market, hasappeared, which uses live vaccine strains of the geneticallymodified ADV as an expression vector of the gene codingfor the immunogenic proteins of other viruses, such as CSF(135). These ‘hybrid’ viruses protect the vaccinated animalagainst both AD and CSF. Moreover, in-depth knowledgeof the molecular biology of the ADV has led to the creationof recombinants that cannot be shed by the vaccinatedanimal in an infectious form. Such recombinants can,however, spread from one cell to another in the inoculatedorganism, as do conventional live vaccine strains, but inrather limited sites (53).

Finally, one should not overlook the considerable progressthat has been made with immunological adjuvanttechnology, even though this is not directly linked withmolecular biology. We have seen the emergence of vaccines


against AD that are produced by tank-mixing a liveattenuated strain with an adjuvant comprised of mineraloils. At the same time, the nature of the oils used inadjuvant composition has evolved, as has emulsiontechnology, making the vaccines increasinglyimmunogenic and considerably reducing local reactions atthe site of injection.

ELISA kits which are available commercially use indirect orcompetitive techniques for measuring antibody levels.When marker deleted vaccines are used, several types ofkits can be employed to detect specifically the infectedvaccinated animals; the ELISA tests that detect gE antibodies are the most commonly used in the field inEurope, whereas tests that detect gG (NSP) or gC antibodies are used more frequently in the UnitedStates of America (USA) (89, 144). A combination ofseveral kits is often used in the framework of controlprogrammes against AD, such as gE kits associated withkits that detect gB antibodies or antibodies against thewhole viral proteins. The latter two kits are used mainly inunvaccinated herds or regions where vaccination is notcarried out; but they can also be used to interpret the herdstatus in regard to infection (gE+; gB+) or vaccination (gB+;gE–). As well as testing sera, the ELISA can be adapted totest filter paper disks that have been moistened with a small quantity of blood obtained by puncturing asuperficial vein (144). This technique is convenient fortesting large numbers of pigs. The disks are air-dried beforeshipment to the laboratory. Moreover, muscular exudatescan also be used as alternative biological samples as thesekits have been evaluated taking serum samples as thereference; the individual sensitivity of the test was 93.2%and the individual specificity was 98.3% (64).

Requirements for the detection of gE, gB or global viralantigen have been defined by several competentauthorities. When comparing different serological tests thatdetect AD antibodies, the sensitivity of ELISA tests appearsvery good and the blocking ones often appear a little moresensitive than indirect ones, allowing earlier detection ofmore than 95% of infected pigs (88).

Marker vaccines used against bovine herpesvirus-1Bovine herpesvirus-1 (BoHV-1), classified as analphaherpesvirus, is a major pathogen of cattle. Primaryinfection is accompanied by various clinical manifestationssuch as rhinotracheitis, pustular vulvovaginitis, abortion,and systemic infection in neonates. Following clinicalrecovery, a life-long latent infection is established in thenervous sensory ganglia of infected animals.

BoHV-1 is a pathogen that is found throughout the worldand which displays significant differences in regionalincidence and prevalence depending on geographicallocation and breeding management (1). BoHV-1 isresponsible for significant financial losses incurred throughdisease and trading restrictions within the cattle industry,prompting the development of control programmes inNorth American herds. Based on serological surveys,several studies have aimed at identifying the risk factors forBoHV-1 seropositivity. Some of them are well characterised,e.g. age, sex (males are more frequently positive thanfemales) and herd size (11, 107). Direct animal contacts,such as purchase of cattle and participation in cattle showswere also found to be important risk factors for theintroduction of BoHV-1 (132, 133, 134). Other factorssuch as farm density or cattle density may increase the riskof BoHV-1 introduction (139). As reported for otherdiseases caused by herpesviruses in man and animals, thelatency-reactivation cycle has a deep epidemiologicalimpact since it is responsible for the maintenance of BoHV-1 in a cattle population. BoHV-1 infection of newgeneration cattle by latent carriers submitted toreactivation/re-excretion stimulus can occur at severaldifferent times, e.g. at birth (118), at mating, duringtransport (117) or following the introduction of heifersinto a group of dairy cows. Therefore, the detection ofBoHV-1 latent carriers is the main concern in the setting upof BoHV-1 control programmes. Moreover, sanitarymeasures must be taken to prevent the introduction ofseropositive animals or even animals originating from aseropositive herd in order to improve vaccine programmeefficacy.

Depending on the seroprevalence of BoHV-1, eradicationprogrammes are based either on the detection and theculling of seropositive animals, or on the repeatedvaccination of infected herds. The use of vaccines tocontrol BoHV-1 infections has evolved over the last fewdecades: previously they were used simply as an effectivemeans of reducing the clinical impact of the disease,whereas nowadays vaccination programmes areimplemented with the additional intent of preventingtransmission, although this is not as readily achievable as areduction in clinical signs. Indeed, BoHV-1 vaccines arenot efficacious at preventing BoHV-1 infection andestablishment of latency. Moreover, vaccine schemes mustbe accompanied by strict management measures to preventthe reintroduction of BoHV-1 into the cattle herd.Therefore, BoHV-1 control programmes may take a longtime to eliminate this well-adapted virus infection of cattle.

Currently available and future bovineherpesvirus-1 marker vaccines

In Europe, several countries have initiated controlprogrammes aimed at BoHV-1 elimination and some


countries are already BoHV-1-free (Finland, Sweden,Denmark, Switzerland and Austria). In this context, theability to differentiate infected from vaccinated animals(known as the DIVA strategy) was critical for preventingtrading restrictions in Europe. To set up the DIVA strategy,marker vaccines and reliable companion tests were developed.

On the one hand, the marker vaccines must include BoHV-1 antigens able to induce a protective immuneresponse. On the other hand, they consist either of subunitvaccines or of BoHV-1 strains from which a gene encodinga non-essential glycoprotein has been deleted. The deletedglycoprotein must be expressed by all BoHV-1 field strainsand induce a detectable immune response. It should alsobe a virulence factor of BoHV-1 in order to ensure a furtherattenuation of the marker vaccine strain by the deletion ofits gene.

Non-essential BoHV-1 glycoproteins gC, gE, gI, gG and gMmay be deleted to construct BoHV-1 marker vaccines. Fourcandidate deletion mutants (BoHV-1 gC-, gM-, gI- and gG-null mutants) do not correspond to the above-mentionedrequirements. BoHV-1 gC-null mutants retain virulence inthe natural host (56) and BoHV-1 gM-null mutants havenever been tested in vivo (61). BoHV-1 gI-null mutants arenot sufficiently immunogenic (56). BoHV-1 gG-nullmutants are easily reactivated from latency (56) and gG-specific antibody tests are not available.

Evidence of consistent results led to the selection of theBoHV-1 gE-null mutant as a candidate BoHV-1 deletedmutant for use as a marker vaccine. First, it was shown tobe immunogenic (56) and to possess very little residualvirulence (127). Moreover, BoHV-1 gE was shown to beexpressed in a very large subset of BoHV-1 field strains(101) and a gE-specific antibody test has been developedas a companion test for the differentiation of vaccinatedfrom infected animals (66, 130). The development of aBoHV-1 marker vaccine took advantage of the knowledgegained from ADV control and marker vaccines based onADV gE-null mutants have successfully been developed forthe control of ADV (137).

Several studies have been conducted, and others are still inprogress, to produce new generation vaccines againstBoHV-1. Ideal marker vaccines should combine high levelsof safety and efficacy. Several subunit vaccines have beentested. They consist mainly of glycoproteins B, C or Dexpressed in different systems such as transfected cellcultures (126), recombinant baculoviruses (125),recombinant adenoviruses (42, 43, 100, 148), orrecombinant tobacco mosaïc viruses (96). The gD-basedsubunit vaccines are the most efficacious at reducingclinical disease and virus excretion when they areformulated with effective adjuvants. For example,chitosans (42) and CpG oligodeoxynucleotides (54, 86)

are new adjuvants that significantly enhance the protectiveimmune response, as evidenced by increased neutralisingantibody titres and reduced clinical disease and viralshedding following challenge. The latest vaccineapproaches consist of plasmid DNA vaccines containingsequences encoding for the three major immunodominantBoHV-1 glycoproteins gC (50), gB (71) or gD (87, 120,121). These constructs could potentially be administeredby needle-free delivery methods which would help toprevent losses due to the tissue damage that classicalvaccine delivery methods can cause (54, 124).

The biological properties

of glycoprotein E (gE)-deleted bovine

herpesvirus-1 marker vaccines

As for the majority of the BoHV-1 vaccines, markervaccines are very effective at preventing clinical signs afterchallenge with highly virulent strains (55). However, noneare able to fully prevent infection by the challenge strain,which establishes a latent infection, and might be re-excreted following a reactivation stimulus. New vaccineformulations and protocols have therefore been developedin order to improve the viral protection. Equivocal resultswere obtained when the two forms (inactivated and liveattenuated) of the same marker vaccine were tested. Whenit was administered twice to seronegative cattle, theattenuated marker vaccine induced a better viral protectionthan the inactivated marker vaccine after challenge (12).However, the inactivated vaccine was more efficacious atreducing virus excretion after reactivation of latentlyinfected calves than the live attenuated vaccine (13). Aninteresting approach was to combine the use of theattenuated vaccine as the priming dose and the inactivatedvaccine as a booster injection to complete the primarycourse of vaccination. This kind of protocol was shown tobe the most efficacious at reducing virus excretionfollowing challenge (44, 58). The immune status of aBoHV-1 latent carrier is the key factor controlling viral re-excretion following a reactivation stimulus. Therefore,latent carriers must be repeatedly vaccinated at regular 6-month intervals in order to maximally decrease the riskof re-excretion (34).

The efficacy of the DIVA vaccines was demonstrated in twofield trials. In the first trial, a significant decrease in thenumber of gE seroconversions was observed in herdswhere the gE-deleted vaccines were used (77). The secondstudy demonstrated that repeated vaccination using eitherinactivated or live attenuated gE-deleted BoHV-1 vaccinesis efficacious at reducing the incidence of gE seroconversion in dairy cattle and consequently theherd prevalence of gE-positive animals (34). This studyshowed the superior efficacy of a protocol whereby all ofthe herd is vaccinated together at regular 6-month intervals


compared to protocols where all of the herd is vaccinated,but not all at the same time (34).

Three safety concerns about the live attenuated gE-deletedvaccine have to be addressed. First, gE-null BoHV-1 wasdemonstrated to establish a latent infection (67, 128) andto be re-excreted following experimental stimuli (67, 105)and in field conditions (35). However, there is so far noevidence that this deletion mutant can persist in the cattlepopulation (78).

A second concern rose from the production of seronegativeBoHV-1 latent carriers following the use of BoHV-1 markervaccines in passively immunised calves. Indeed, passivelyacquired colostral immunity interferes with an activeantibody response following infection. It has beenexperimentally demonstrated that gE-negative BoHV-1vaccine, when used in passively immunised calves, givesrise to seronegative vaccine virus carriers (67).

The third concern is the potential for BoHV-1recombinants to arise after co-infection of animals with areplicative gE-deleted BoHV-1 strain and a virulent BoHV-1 field strain (115, 116). One field observation and twoexperimental findings underlie this concern:

a) the isolation of a gE-deleted BoHV-1 vaccine strain incows vaccinated eight months before (35)

b) the frequent appearance of BoHV-1 recombinants in co-infected calves (105)

c) the experimental isolation of a virulent gE-deletedBoHV-1 recombinant (84, 85).

Properties of companion diagnostic tools

Even if the DIVA strategy has been demonstrated to beefficacious, it presents some weaknesses (7). Indeed, thestrength of the tool is fully dependent on the capacity ofthe diagnostic test to detect BoHV-1 gE-specific antibody.But the sensitivity of the only available gE-specific ELISA isaround 70% (62, 97). This rather low level of sensitivityhas a 30% false-negative rate in individual tests but itremains sufficiently high for use at infected-herd level. Theproblem of the low sensitivity of this test is compoundedby the weak level of the delayed immune response raisedagainst BoHV-1 gE, which means that it can be as many as42 days after infection before gE antibodies can be detected(7). The specificity of the gE-specific ELISA test is 92%(62). Although it is an acceptable level in the first steps ofa control programme, this lack of specificity will beresponsible for several misleading false positive results inherds where BoHV-1 has been eradicated. In these herds, aserial combination of serological tests should beperformed. The Danish test system (consisting of ablocking and an indirect ELISA), which was used in the

BoHV-1 eradication programme in the Netherlands, has avery high sensitivity (> 99.0%) and a very high specificity(> 99.9%) (29). Finally, a useful approach for dairy cattleherd monitoring is the regular serological testing of milktank samples (140). A positive result is obtained when15% of the dairy cows are seropositive towards BoHV-1.This level of seropositivity is rapidly obtained in cases ofBoHV-1 introduction into a previously negative herd.

Marker vaccines used against classical swine feverClassical swine fever, previously known as hog cholera, isstill a serious threat for the domestic pig population as it isa highly contagious viral disease of worldwide importance.Pigs and wild boars are the only natural reservoir of CSFvirus (CSFV). CSFV, bovine viral diarrhoea virus (BVDV),and border disease belong to the genus Pestivirus of theFlaviviridae family. These are small, enveloped, positivesingle-stranded ribonucleic acid (RNA) viruses. The pigletsdevelop more evident clinical signs than the adults. Theusual clinical sign is hyperthermia, which is usually higherthan 40°C in piglets (which pile together in the corner) butin adults it can be lower (39.5°C). The first usual signs of theacute form are anorexia, lethargy, conjunctivitis, respiratorysigns and constipation followed by diarrhoea. The chronicform of the disease is generally fatal. Often the infected pigspresent jaundice and cyanosis before death (65).

Currently available classical swine fever vaccines

Two live attenuated vaccines have been used successfullyfor many years. The live vaccines include the Chinesestrain also known as C strain vaccine, which wasattenuated by serial passages in rabbits and later adapted tocell cultures (136), and the Thiverval strain derived fromthe virulent Alfort strain through more than 170 serialpassages at 29°C to 30°C (4, 63). These traditional livevaccines induce a high level of protection against thedevelopment of clinical signs and neutralising antibodies attwo weeks post challenge. Dewulf et al. (32) demonstratedthat no virus transmission was detectable even when thepigs were challenged on the same day as the vaccination.The vaccinal protection lasts at least six to ten monthswhatever the immunisation route used: intramuscular ororonasal (57, 114). The main problem of using these livevaccines is that it is impossible to distinguish antibodiesthat are the result of vaccination from those that are due tonatural infection.

To clear up this difficulty, different teams have worked onthe development of marker vaccines. CSFV envelope


glycoprotein E2 is the major protective immunogenicprotein responsible for eliciting neutralising antibodies andconferring protective immunity against the virus and it hasbeen demonstrated to be a highly conformationaldependent immunogenic protein (70, 149). Different typesof subunit or marker vaccines have been developed as non-replicative ADV expressing the E2 of CSFV (94), or livevectors such as porcine adenovirus. DNA vaccines havealso been developed (3) but as yet these do not induce anyreal protection in pigs. Different vaccine schemes orcombinations have been used such as: a prime-booststrategy (DNA-adenovirus) (52) or a co-administrationwith some interleukin (IL) recombinant protein such as IL-3, 12 or 18 or via a DNA vector (2, 141).

At the present time, only two E2 recombinant proteinsubunit vaccines produced in the baculovirus expressionsystem have been licensed for market use. The efficacy ofthese two commercially available E2 marker vaccines hasbeen extensively assessed in different vaccination-challenge and transmission trials. The results of theseexperiments were rather variable. A single vaccination witha vaccine dose of 32 µg of E2 in a water-oil-water adjuvantprevented clinical signs and mortality following a CSFVchallenge three weeks after vaccination (15). At least 14days were needed to obtain clinical protection in growingpigs vaccinated with a single dose (14, 123), but in the caseof earlier challenge, no protection against the disease andno reduction of virus shedding has been demonstrated(123). The ability of the two marker vaccines to preventtransplacental transmission of CSFV has also beenevaluated. The results showed that with a doublevaccination, virus spreading by transplacental infectionunder the conditions of emergency vaccination could notbe prevented in most of the vaccinated animals and couldlead to the carrier sow syndrome and, consequently, to thelate onset form of CSF (30). Based on the results of usingthe double vaccination protocol on pregnant giltschallenged 46 days after the second immunisation, it wasconcluded that double vaccination with an E2 subunitmarker vaccine protects pregnant gilts from the clinicalcourse of the disease but does not prevent horizontal norvertical spread of the CSFV (31). Despite the fact that theseresults indicated that the efficacy of these vaccines was notideal, their use in an emergency vaccination protocol hasnot been banned by the European Commission (EC).

Properties of companion diagnostic tools and their sensitivity and specificity limits

Discriminatory companion ELISA tests are based on thedetection of antibodies to the Erns protein. In 1999, sixteennational swine fever laboratories participated in testing thediscriminatory ELISAs. The two available kits were testedfor sensitivity, specificity, reproducibility and practicability.Reference sera (CSFV and BVDV antibody positive) and

field sera were used as well as sera from the weaner andsow experiments carried out during the marker vaccinetrial. Both discriminatory ELISAs were less sensitive thanconventional CSF antibody ELISAs, although there wasconsiderable variation between them. Neitherdiscriminatory ELISA consistently detected the marker-vaccinated, CSF-challenged weaner pigs correctly as ‘CSFpositive’, although CSF-challenged pregnant sows wereidentified correctly. The limitations of these discriminatoryELISAs would prevent the use of the two licensed markervaccines under emergency field conditions (40).

In 2003, the EC supported another large-scale inter-laboratory trial to assess the performance of a new versionof a companion Erns ELISA test. It was concluded that evenif the specificity and the sensitivity of the test was betterthan the previous kits tested in 1999 (40), there was still aneed for more reliable tests to be sure that a vaccinated pighas not been infected and is not a virus carrier.

Marker vaccines used againstfoot and mouth diseaseFoot and mouth disease is a highly contagious disease ofdomestic and wild cloven-hoofed animals including cattle,sheep, goats and pigs. It is caused by a virus (FMDV) of thegenus Aphthovirus, family Picornaviridae and exists asmultiple serotypes and subtypes; it causes severe economiclosses through decreased livestock productivity and traderestrictions. The virus is widely distributed and the diseaseis completely absent only in the European Union (EU) andin the Australasian and North American continents.

Current vaccines and their biological propertiesin the framework of eradication and control

In areas with endemic FMD, vaccination is commonly usedin conjunction with zoosanitary measures to minimiselosses and reduce virus circulation. In FMD-free countries,such as those of the EU and North America, the policy forcontrolling outbreaks has been primarily based upon‘stamping out’, i.e. slaughtering of infected and contactanimals together with restrictions on the movement ofanimals and animal products. Nevertheless, provision isretained to vaccinate under emergency circumstanceswhere an outbreak is or threatens to become extensive.During and after the 2001 FMD outbreaks in Europe therewas a growing desire to place more emphasis on a‘vaccinate-to-live’ policy to reduce reliance upon large-scale slaughter of herds at risk of becoming infected.According to such a policy, the stamping out of infectedpremises and the imposition of movement restrictionswould be accompanied by a limited period of emergency


vaccination of surrounding herds, followed byserosurveillance to detect and eliminate infected animalsnot identified on the basis of clinical disease orepidemiological tracing. In support of this policy, newregulations have been approved by the World Organisationfor Animal Health (OIE) and the EU so that countries usingthis approach can now regain their FMD-free status sixmonths after the last infection has been reported ratherthan one year later as was previously the case (39, 145).

Current FMD vaccines are produced by infectingsusceptible cell cultures (most frequently baby-hamsterkidney cell lines) with virulent FMDV, followed bychemical inactivation with binary ethyleneimine andpurification by ultra filtration. At formulation, antigen ismixed with either an aluminium hydroxide and saponinadjuvant to make an aqueous vaccine for use in ruminantsor is emulsified in oil to make a vaccine for theimmunisation of pigs and ruminants. These vaccines havebeen used successfully for decades to control FMD andregular mass vaccination, mainly of cattle, has helped inthe eradication of the disease in some regions such asEurope and South America. Emergency vaccine banks havebeen established by national and international agencies,holding reserves of concentrated unformulated antigenfrozen over liquid nitrogen (36). These may be formulatedat higher doses than would be used for prophylacticvaccination so as to induce a rapid onset of immunity afteradministration as a single dose.

Nevertheless, there are a number of concerns andlimitations with the use of conventional vaccines inemergency control programmes. Their production requiresthe growth to high titre and subsequent completeinactivation of virulent strains of FMDV. Although this isconducted within high containment facilities there is stillthe potential for escape of live virus from these facilities orfor inadequate inactivation of virus and these concernshave led some FMD-free countries to prohibit vaccinemanufacture on their territory. Conventional FMD vaccinesare more difficult to standardise than vaccines produced bysynthetic or recombinant techniques and final producttesting for safety and efficacy still requires in vivo testing inanimals. As mentioned earlier, most vaccines are preparedfrom concentrated cell culture supernatants from FMDVinfected cells and therefore contain variable amounts ofviral NSP. Induction of antibody to NSP by vaccines‘contaminated’ with residual amounts of these proteinsmakes it difficult to identify infection in vaccinatedpopulations by the use of NSP antibody tests (see ahead).In addition, a consistent cold chain is required in the fieldfor the vaccine to remain efficacious. Althoughconventional vaccines can prevent clinical signs and spreadof the disease in vaccinated animals, they do not induce asterile immunity and therefore may not prevent virus-exposed animals from becoming acutely infected, and aproportion of such animals will become persistently

infected virus carriers (25, 90, 91) whose presencejeopardises recovery of FMD-free status. Moreover, fullprotection takes time to develop and is short-lived withoutrepeated booster doses (27, 37). Even when emergencyvaccine was administered with a ten times greater antigenpayload than the normal dose it could not fully protectvaccinated cattle from a severe challenge at ten days postvaccination (Cox and Barnett, unpublished results).

Possible future vaccines

Much work has been done on the development ofalternative vaccines, including subunit vaccines based onhighly immunogenic FMDV proteins or peptides and DNAvaccines (10, 26, 33, 41, 59, 60, 69, 99, 109), but theirimmunogenicity has been found to be much lower thanthat of conventional FMD vaccines.

Efforts to produce attenuated FMD vaccines by theadaptation and further passage of FMDV in non-susceptible hosts have been unsuccessful due to thereversion of the attenuated viruses to virulent forms (76).Targeted deletion of the Lpro gene, which is not essential tovirus replication, produced a vaccine that induced a goodFMD-specific neutralising antibody response, but couldnot protect fully (23, 79). Although a recombinant virus inwhich the RGD receptor binding site was deleted inducedprotection in natural hosts (74), with such a virus there ispotential for selection of virus variants that could entercells by utilising other receptors (5, 6).

Another approach has been to produce a vaccine whichexpresses the entire virus capsid, and therefore all of theimmunogenic sites present on intact virus, but lacks theinfectious nucleic acids (8, 48, 49, 68, 102). Using thisstrategy, the Plum Island Animal Disease Center in the USA(47, 80, 83, 147) inserted the complete capsid codingsequences of FMDV into a live replication-defective humanadenovirus vector, along with the FMDV 3C proteaseneeded for capsid assembly. One parenteral inoculationwith this vaccine induced antibody and clinical protectionwithin seven days. The same adenovirus vector expressingthe cytokine porcine interferon-alpha could protectanimals from FMD for three to five days within one day ofvaccination (22, 47).

Properties of companion diagnostic tools and their sensitivity and specificity limits

Conventional FMD vaccines are mainly comprised of viralstructural proteins (SP) plus RNA and contain only traceamounts of viral NSP synthesised during viral replication.Furthermore, the amount of residual NSP present invaccines can be reduced by additional purification stepsduring antigen preparation. Therefore, conventionalvaccines elicit a mainly anti-SP antibody response, whereas


infection with replicating virus elicits antibodies to both SPand NSP. Consequently, serological methods which detectantibodies to FMDV SP such as the liquid phase blockingELISA (51), the solid phase competition ELISA (73) or thevirus neutralisation test (45) cannot distinguish betweeninfection and vaccination with conventional vaccines.However, ELISAs that measure antibodies to different NSP(3ABC, 3AB, 3A, 3B, 2A, 2B and 2C) can be used asmarker tests to detect infection in conventionallyvaccinated animals (17, 26, 28, 75, 98, 103, 106, 108).Incomplete purification of vaccine antigen as well asmultiple vaccination increases the likelihood of inducingNSP antibodies, but the latter will not arise after emergencyvaccination of previously naïve animals.

To date, the most promising NSP tests have been those thatdetect antibody to NSP 3ABC, and the OIE index methodis an indirect 3ABC screening ELISA (first developed inSouth America [NCPanaftosa]) supported by aconfirmatory immunoblotting test against NSP 3A, 3B, 2C,3D and 3ABC (143). A number of commercial 3ABCELISA test kits have recently become available and theirsensitivity and specificity were compared to one anotherand to the index screening method at a workshop inBrescia (Italy) in 2004 (16). The specificity of the testsranged between 97% and 98%, including when used totest cattle that had been given a single dose of Europeanvaccine. All of the tests were highly sensitive for detectionof infection in unvaccinated cattle, whereas the sensitivityof the tests to detect viral carriers in vaccinated andsubsequently infected cattle ranged from 68% to 94%depending on the test used. The workshop concluded thattwo tests performed comparably to the OIE index method(Ceditest® FMDV-NS, Cedi Diagnostics B.V. and 3ABCtrapping-ELISA, IZS-Brescia) of which the Ceditest® is theonly one available as a commercial kit.

Guidance on how to carry out post-outbreakserosurveillance for FMD in vaccinated populations isprovided by the OIE Terrestrial Animal Health Code(Terrestrial Code) (145) and by the European Directive onFMD control (39). The Terrestrial Code requires that herdscontaining seroreactors must be followed up to determinewhether these contain infected animals or not; findingevidence of infection at any stage automatically invalidatesfreedom from infection status. The European Directive onFMD control specifies that serosurveillance should becarried out at least one month after an outbreak hasfinished or one month after the last use of vaccine,whichever is the later. Further, it states that the entirevaccinated population should be sampled and tested orenough should be sampled and tested to give 95%confidence to detect a within-herd prevalence of infectionof 5%.

The problem of some vaccinated animals becomingcarriers without seroconverting to NSP can be overcome by

interpreting NSP test results on a herd basis (104),although this still leaves a lack of certainty over freedomfrom infection in small herds (46, 92), since a test with80% sensitivity at the individual level requires at least twoinfected animals in the herd to be sampled to have 95%confidence of detecting at least one of them (93). Imperfecttest specificity can be partly overcome by retesting positivesamples. For example, with the Ceditest® at the Bresciaworkshop, discounting the positive results that were notconfirmed on Cedi retest increased the specificity to 99.2%and decreased the sensitivity from 86.4% to 85.1% (93). Afurther increase in test specificity could be achieved by asecond retesting of Ceditest-confirmed positive samplesusing another non-covariant, commercially available NSPassay (SVANOVIR™ FMDV 3ABC-Ab ELISA, Svanova,Upsala, Sweden), resulting in an overall specificity andsensitivity of 99.98% and 71.2% respectively (93).

Foot and mouth disease is therefore a good example ofwhere advances in vaccine production technology toreduce contamination of vaccines with NSP antigens,together with advances in diagnostic techniques to detectantibody to these antigens, have resulted in thedevelopment of marker vaccines and companiondiagnostic tests that are sufficiently robust that they haveresulted in amendments to FMD control policy such that apolicy of ‘vaccinate to live’ is now supported in appropriatecircumstances. Improved FMD marker vaccines and testsmay be available in the future. For example, theexperimental adenovirus vectored vaccines describedabove express recombinant viral capsids that are devoid ofNSP 3D, which is a protein that elicits a strong antibodyresponse but cannot be eliminated from conventionalvaccines by purification (81). This would enable use of acompanion marker test for infection based on detection ofanti-3D antibody (47). Testing of saliva for FMDV-specificIgA is also a promising tool for detection of infection in animals given conventional vaccine by the parenteralroute (90).

Marker vaccines used

against avian influenzaAvian influenza viruses all belong to the InfluenzavirusA genus of the Orthomyxoviridae family. They areenveloped, negative-stranded RNA viruses with asegmented genome, consisting of 8 genes (PB1, PB2, PA,HA, NP, NA, MA and NS). AI viruses may be classified onthe basis of the severity of the clinical signs they cause insusceptible birds. Low pathogenicity AI (LPAI), may becaused by viruses belonging to all 15 haemagglutinin types(H1-H15) and produce a mild disease in susceptiblepoultry characterised by respiratory and enteric signs thatare often associated in breeders and laying hens withreproductive disorders. Some LPAI viruses are termed


mildly pathogenic AI viruses. Highly pathogenic AI (HPAI)is, in contrast, a systemic viral disease of poultry withmortality that approaches 100% in many gallinaceousbirds. The clinical disease HPAI is caused only by virusesof the H5 and H7 subtypes that contain multiple basicamino acids at the deduced sequence of the cleavage site ofthe precursor of the haemagglutinin molecule. The mainclinical signs presented by HPAI-infected poultry areanorexia, depression, cessation of egg-laying, followed bycomplete reluctance to move and tremors of the head,paralysis of the wings and incoordination of the legmovements (19).

Marker vaccines and companion

diagnostic tests for notifiable avian influenza

Increased knowledge of AI occurrence and epidemiologyhas driven a revision process of the definition of AI forinternational trade regulations laid down by the OIE. Therevised Chapter on AI now reads ‘For the purposes of thisTerrestrial Code, avian influenza in its notifiable form (NAI)is defined as an infection of poultry caused by anyinfluenza A virus of the H5 or H7 subtypes or by any AIvirus with an intravenous pathogenicity index (IVPI)greater than 1.2 (or as an alternative at least 75% mortality)as described below. NAI viruses can be divided into highlypathogenic notifiable AI (HPNAI) and low pathogenicitynotifiable AI (LPNAI)’ (146). The aim of this section is toreview currently available marker vaccines and companiondiagnostic tests for NAI viruses of the H5 and H7 subtypes.

Research in AI vaccinology has only recently become afield of interest for pharmaceutical companies and forresearch institutions, and for this reason the selection ofproducts and performance of companion diagnostic testsare not adequate to cover fully all the complex fieldsituations this infection may cause.

Antigenic cross-reactivity between strains of the same Hsubtype is believed to occur even between strainsbelonging to different lineages. However, how cross-protection will be influenced by immunological pressuregenerated by the variety of seed strains is currentlyunknown (112). Similarly, the occurrence and extent ofantigenic drift in this situation is impossible to predict, butcould become a significant issue in the future.

Inactivated conventional vaccines

and companion diagnostic tests

or systems to reveal field exposure

These vaccines are based on a preparation containinginactivated virus grown in embryonated eggs. The seedstrains that are currently being used are field isolates

collected from natural outbreaks, selected without definedcriteria. For this reason they may contain seed viruses of either high or low pathogenicity, although the OIE guidelines indicate that LPNAI strains should be used (146).

In order to be efficacious, inactivated conventionalvaccines must contain a seed virus of the same H subtypeas the field strain against which vaccination is directed,while the subtype of the other surface antigen, theneuraminidase protein (N), is virtually irrelevant withregard to protection (111). Thus, vaccines may contain aseed virus of the same subtype as the field strain (H5N1vaccine to combat an H5N1 field challenge) or may be ofthe same H subtype but of a different N (H5N9 vaccine tocombat an H5N1 field challenge). The latter is known asheterologous vaccination.

Currently there are two methods of detecting fieldexposure with this type of vaccine that have been evaluatedin the field with satisfactory results.

The introduction of unvaccinated sentinels into the shedhas been used as a method of identifying field exposurewithin a vaccinated population, regardless of the strainused in the vaccine. This system requires the identificationof unvaccinated birds and regular clinical inspections inconjunction with serological testing to detect LPNAI,HPNAI being clearly visible as clinical pathology in thesentinels. The system is deemed to be valid, but requirespreparatory work and is more time consuming, especiallywhen the number of herds to be vaccinated is very high,and particularly when birds that are not confined to cagesneed to be identified within the flock. Furthermore, therisk that sentinel birds could be substituted with naïvebirds in order to escape restriction policies exists.

In the case of heterologous vaccination, it is possible to usethe diversity between the N antigen contained in thevaccine and the one in the field as a natural marker system.This DIVA system was developed in Italy in 2001, and hasbeen successfully used to combat multiple introductions ofNAI (18). The system is based on the detection ofantibodies to the N protein of the field virus, whichrepresent evidence of field infection. Currently, only anindirect immunofluorescence antibody test has been fullyvalidated (20, 21).

An encouraging system that can be used as a companiontest to vaccines containing homologous or heterologousseed strains, is based on the detection of anti-NS1antibodies (122). This system is based on the fact that theNS1 protein is synthesised only during active viralreplication and is therefore not present in significantamounts when inactivated vaccines, that do not replicatein the bird, are used. Birds that are vaccinated with such


vaccines will develop antibodies to the NS1 only followingfield exposure (38). Full and field validation of this systemunder different circumstances is still in progress (H. Chen,personal communication) and should be made availablebefore this system is recommended. No diagnostic kit hasbeen validated to date.

Engineered vaccines and companion tests

Engineered vaccines include all vaccines that are notnatural isolates or natural reassortants. These include:recombinant live vectored vaccines and vaccines based onreverse genetics and recombinant proteins.

Recombinant live vectored vaccines are based on insertingan H5 or H7 haemagglutinin gene in a suitable, replicatingvector which will, during its replication, induce theproduction of antibodies to the haemagglutinin of theinfluenza gene. Fowlpox-based recombinant viruses haveobtained marketing authorisations and are being usedcurrently in several countries. Newcastle disease virus(NDV)-based recombinants have been developed byseveral groups (H. Chen, personal communication; 113, 138), with a product developed by Chineseresearchers being used currently in the field in the People’sRepublic of China. An infectious laryngotracheitis-basedproduct has also been described (72).

All these preparations, with the exception of the onedeveloped by Swayne (113), offer protection from clinicalsigns and reduce shedding levels. However, for most ofthese products, their efficacy in the presence of pre-existing antibodies due to natural infection with a fieldstrain of the vector virus, e.g. NDV or fowlpox virusremains to be established (111, 113).

The greatest advantage to the use of these products is thatcompanion diagnostic tests directed to detect antibodies toany viral proteins other than the haemagglutinin may beused to identify field-exposed flocks. Thus, the agar gelimmunodiffusion or ELISA tests directed to the detectionof antibodies to the NP or M proteins, can be successfullyused, and enable the detection of field challenge caused byany influenza A virus. Tests directed to the detection ofantibodies to the N protein, identify field exposure only toviruses of known N subtype.

Inactivated vaccines generated by reverse genetics haverecently been developed in the USA and in the People’sRepublic of China (119). The seed strain contained in thevaccine is basically a synthetic virus, completelyengineered in the laboratory. These viruses contain abackbone derived from a virus that has high replicationcapacities (A/Puerto Rico/8/XX) with the two genesencoding for surface antigens (H and N) derived fromcontemporary viruses. This combination of genes allows

on the one hand an excellent replicative efficiency – whichensures high titred, consistent virus yields duringproduction – and on the other, suitable surface antigens.Since these vaccines have the same properties asconventional inactivated vaccines, the same companiontests apply.

Recombinant protein-based vaccines are synthesised in thelaboratory by expressing the haemagglutinin in a suitablesystem, for example baculoviruses, plants and yeasts (110).Several prototypes have been generated and have beentested in the laboratory with encouraging results, however,probably due to the cost of production, they have notattracted any commercial interest to date. The use of any of these ‘engineered’ vaccines in the field would haveseveral advantages, including the possibility of using avariety of companion diagnostic tests, as is the case withrecombinant vectored vaccines – and of course, of updating the haemagglutinin component should this be required.

In summary, to date, only conventional inactivated(containing natural or synthetic strains) and recombinantlive vectored vaccines are available for use and can becoupled with a suitable companion diagnostic test. Bothcategories have some advantages and limitations in theirapplication in the field, and certainly, considering thecomplexities of these vaccines and the need to extend theiruse, more research is needed to optimise products andcompanion tests in order to tackle the current limitationsto their use in the field.

Limitations and advantages of the use of marker vaccinesIn spite of the major progress that has been made as aresult of the development of marker vaccines, it would bea mistake to consider that their use could simply replacesanitary prophylactic measures. Indeed, past experience isvery useful for assessing the limits and the advantages ofthe use of these marker vaccines, which could be apowerful tool in a set of measures to control and eradicatea contagious disease. However, the use of such vaccineshas to be adapted to the epidemiological situation, thecontagiousness of the disease concerned and to thepresence or absence of conditions with the capacity toinfluence the spread of infection. To control a disease, thekey point is to detect clinically inapparent infected animals(healthy carriers) which can infect in-contact susceptibleanimals. When vaccination is used, the critical stage ofalert induced by the appearance of clinical signs isremoved or suppressed. For this reason, such vaccineshave to be as efficient as possible, not only to protectvaccinated animals against clinical signs, but also to


prevent, as far as possible, the excretion of the virus byvaccinated and subsequently infected animals. Moreover,the sensitivity of the diagnostic kits should be as high aspossible to reduce to the greatest possible extent, theprobability of false negative results; indeed, in such astrategy, the epidemiological consequences of false positiveresults are less significant than false negative results, aspositive results are generally confirmed (in a second,complimentary phase) by a reference laboratory usinganother diagnosis tool.

The longest experience of using marker vaccines has beenaccumulated in relation to the control and eradication ofAD. In this case, the use of deleted marker vaccines hasrepresented a considerable advance in programmes tocontrol the disease in several countries.

First, these vaccines have made mass vaccination possible,whilst retaining the means for serological detection ofinfection. This has enabled vaccinated herds whichsubsequently become infected to be pinpointed so that thenecessary measures can be applied to prevent the fieldvirus from spreading further.

Second, it has become possible to implement sanitarymeasures in a gradual manner in vaccinated, infectedherds, by culling the infected sows at varying speeds, asrequired. These infected sows are detected throughserological screening using the ELISA technique, whichenables vaccinated pigs to be distinguished from those thathave been vaccinated and then subsequently infected.

This means that vaccination has a combined effect whichallows a programme of prophylactic treatment to be carriedout in total safety. Mass vaccination, conducted severalyears in succession, limits the quantity of virus shed intothe air by the infected pigs, thereby considerably reducingthe probability and scale of the air-borne spread ofcontagion between herds (95, 137). Furthermore,systematic vaccination avoids economic losses due to apoorly controlled infection. Consequently, after severalyears of vaccination in a country or region, and theintroduction of sanitation measures into the infected herds

and the continual culling of the oldest infected sows, theprevalence of infection gradually diminishes; in addition,the incidence of infection remains very low and is keptunder control. However, the cost of vaccination must betaken into account when calculating the total cost of aprophylactic treatment.

Authors compared the cumulative costs, over ten years, ofvarious measures for controlling AD in northern Germany,following the introduction of prophylactic treatment (Table I). Of the five possible strategies, the mosteconomical is based on systematic vaccination, followed byscreening of infected herds and the slaughter of sowspresenting infection-specific antibodies.

Of course, this is a cumulative cost which takes all costsinto account: those of the State, those of tradeorganisations and those of breeders. The authors note thatthe prevalence of infection diminishes during the first twoyears, but that vaccination alone is not enough to eliminateinfection; during the final years of the programme the ADVpersisted in a small number of herds. After 42 months ofvaccination, few herds still harboured infected breedinganimals. The detection and elimination of these breedinganimals lead to a sharp drop in the prevalence of infectionin breeding herds, whilst the risk of infection in fatteningfarms (or of fattened animals in other farms) becomes zero (142).

As a result of past and present experience, it has becomepossible to develop a strategy for using vaccines to controlAD. In countries that have sufficient economic resources toenvisage eradication of the infection, there are two possibleoptions:

– where the prevalence of infection in a given territory ishigh, or there is a high density of pig herds, massvaccination with effective deleted vaccines is the onlymeans of reducing prevalence; however, although thesemeasures are necessary, they are not in themselvessufficient to eradicate the infection. Identification,screening and culling of the infected breeding animalsappear to be essential to successful eradication whilst


Table I

Total costs of potential control strategies for Aujeszky’s disease in Germany over the ten years following initiation of prophylactic

treatment (147)

Strategy Cumulated cost over ten years (in thousands of euros)

Vaccination of sows twice per year 18,085

Vaccination of sows three times per year 18,143

Vaccination of sows three times per year, and of pigs for consumption once per year 13,534

Vaccination of sows three times per year, and of pigs for consumption once per year. Serological

controls and slaughter of pigs presenting infectious antibodies (where prevalence is < 10%) 9,907

Control and slaughter of pigs possessing infectious antibodies 19,342

continuing to systematically vaccinate the animals at leasttwo years after elimination of the last infected pig. In thelatter case, it is advisable to control the movements ofpiglets, pigs for consumption and breeding animals asmuch as possible;

– by contrast, in regions with a low herd density and lowprevalence of AD, serological screening and the culling ofinfected breeders or total slaughter of certain herds, appearto be the most effective, and in some cases the mosteconomical, measures for achieving eradication. Suchmeasures have been successfully introduced, for example,in Denmark, the United Kingdom, Sweden and severalregions of France.

However, independently of the performances of thevaccines and the companion kits (which are key issues indetermining the use of such tools), other examples showthat the use of marker vaccines would not have had asignificant impact on the control of the situation. When aserious CSF epizootic hit several European countries in1997, many people believed that the use of these newgeneration serological marker vaccines could prevent afurther animal health catastrophe. However, an analysis ofthe situation that existed when the first CSF outbreaksappeared in the Netherlands revealed that more than 22herds were already infected when the primary outbreakwas identified in the region of Venhorst on 4 February1997. The situation rapidly became dramatic for the regionbecause farmers had already sold piglets before theveterinary administration could isolate the infected zone.This led to a rapid spread of the infection in the south ofthe country.

Under such circumstances, the use of a serological markervaccine would not radically alter the basic nature of theproblem, as it does not obviate the need to identifypotentially infected animals and to take a sample of serumbefore any animals are transported, in other words, tostrictly control the movement of pigs. Indeed, at the startof an epizootic, the success of control measures dependson their being rapidly implemented after the appearance ofthe first outbreak and before extensive, undetected spreadhas occurred. Vaccination is no substitute for basicmeasures to control contagious diseases.

So, as a general rule, as long as CSF has not beeneradicated in the world, there is still a great risk ofreintroduction of the virus in free areas. Farmers andveterinarians are in the best position to detect a newintroduction of CSFV, so they should receive training in thedetection of clinical signs and remain extremely vigilant. Anon-vaccination policy is logical in disease-free states butemergency vaccination may be considered in contingencyplans to avoid destroying millions of pigs. When outbreaksoccur, the use of the traditional live C strain vaccine is as

effective at preventing the spread of virus as culling theneighbouring herds. This strategy can be used after thestart of an epizootic when there are too many outbreaksoccurring at the same time, but this means that the pigs areseropositive and leads to their destruction. For this reason,the development of efficacious marker vaccines andreliable discriminatory tests should be encouraged. As ithas been demonstrated that 14 days are necessary toinduce good protection with the available subunit E2vaccines, their use could be envisaged when severaloutbreaks occur at the same time and the use of strictsanitary prophylactic measures alone may not be enoughto control the disease: vaccinating pigs in the zone aroundthe outbreaks would allow the movement of pigs andprevent mass culling. As these E2 subunit vaccines do notprevent vertical transmission, their use must be limited togrowing pigs. Simulation models will also be useful toolsfor choosing the best control measures to apply, dependingon the epidemiological situation.

At the start of an epizootic, in regions with a high densityof pig herds, ring or zonal vaccination can also beenvisaged in order to prevent the virus from replicating toorapidly and to limit the cost of preventive slaughter.However, in this case, transmission of the virus must belimited and control measures must be properly applied andeffective. Such an approach is particularly pertinent forhighly contagious diseases such as FMD in thosecircumstances under which the air-borne transmission isone of the main epidemiological factors in the spread of thevirus. So, if the first outbreaks appear in an area with ahigh density of susceptible herds and underepidemiological conditions that favour air-borne spread,ring vaccination, implemented on the basis of the results ofmodels and assessment to determine the risks anddirections of spreading, could be useful in limiting thespeed and the extent of the virus dissemination (24).However, due to the ability of vaccination to mask theappearance of clinical signs without preventing infection,vaccinated herds, even with a serological monitoringprogramme, represent a greater risk for undetected spreadthan unvaccinated herds, where monitoring can be basedon clinical inspection alone.

In the case of AI, the use of marker vaccines has provedvery effective in controlling LPNAI infection in turkeys andpoultry (18). Nevertheless, the difficulty of implementingsuch a strategy will depend on the species in which thevaccines are intended to be used and, consequently, on theefficiency of one type of vaccine in regard to one particularspecies. The efficiency of a vaccine and the performance ofa companion diagnostic kit cannot be extrapolated fromone avian species to another, so the use of marker vaccineswill depend on the availability of validated data on theperformance of the vaccine and companion diagnostic kitin the avian species that is to be vaccinated.


In regard to the HPNAI strains, some Asian countries haveimplemented a massive vaccination campaign due to thehigh prevalence of infection in the domestic flocks. Insome countries, such as Vietnam, this strategy seems tohave given good results, but the lack of validated dataprevents drawing definitive conclusions on the beststrategies to use in the face of such complex and difficultanimal health crises.

ConclusionThe power of the combination of a marker vaccine and acompanion diagnostic kit for the control of an infectiousdisease depends not only on the performances of thevaccine and the kit themselves but also on the way inwhich these tools are deployed by the competent authorityfor use in the field. Ideally, both the vaccine and thediagnostic kit should be scientifically assessed by anindependent body following submission of a dossier ofdata in support of an official application for a marketingauthorisation. With respect to tests, at least for those usedin the context of official control and eradicationcampaigns, national or international ReferenceLaboratories should control the quality of each batchreleased onto the market. If several diagnosis laboratoriesare involved in the diagnosis and the surveillance of theinfection and the disease, a Reference Laboratory shouldorganise proficiency tests, the results of which should beused to deliver an agreement to the diagnosis laboratoriesto allow them to carry out the diagnostic tests. Regulatory

systems already exist in most regions of the world (e.g. EU,USA, Japan) to control the quality of vaccines released ontothe market. The situation is more varied with respect tocompanion diagnostic tests as not all regions or countrieshave legislation governing their marketing. Adequatevalidation of tests as ‘fit for purpose’ and appropriatequality control, either by the manufacturer themselves orby official Reference Laboratories, are necessary to ensurethat the test performs as claimed and that all batchesreaching the market are of consistent, high quality. Inaddition, where testing is carried out by multiplelaboratories, experience has shown a clear need for qualityassurance of the testing performed in all participatinglaboratories. This can be achieved by a combination oflaboratories working to recognised quality standards,backed up by external accreditation, and participation inregular proficiency tests conducted by an appropriateReference Laboratory. Only those laboratories reaching therequired standards should be certified as competent to beinvolved in national disease eradication campaigns.

A successful programme can be based on vaccination, butshould also include sanitary measures. Furthermore, whenvaccination is part of a control programme, it should beimplemented only for a certain period of time. Most of thetime, when the prevalence of the infection decreasessignificantly and when the epidemiological unit is correctlyprotected from outside introduction of the agent,vaccination should be replaced by sanitary measures.


Les vaccins à marqueurs et les conséquences

de leur utilisation sur le diagnostic et la prophylaxie


Résumé

La biologie moléculaire et les avancées techniques liées à la recombinaison de

l’ADN marquent le début d’une nouvelle ère en vaccinologie. Les auteurs

examinent le développement récent de vaccins à marqueurs spécifiques ainsi

que les conséquences de leur utilisation sur le diagnostic et la prévention des

principales maladies infectieuses. Les vaccins obtenus par délétion de gène, les

stratégies DIVA (visant à différencier les animaux infectés des animaux

vaccinés) et d’autres méthodes similaires ont été appliqués avec succès pour


Resumen

La biología molecular y, en particular, los adelantos registrados en la técnica de

recombinación de ADN, han marcado el comienzo de una nueva era para la

vacunación. En este artículo se examinan las vacunas marcadoras específicas,

de reciente desarrollo, y las repercusiones de su administración en el

diagnóstico y la prevención de importantes enfermedades infecciosas. Se han

obtenido resultados satisfactorios en materia de control y erradicación de la

enfermedad de Aujeszky, la rinotraqueítis infecciosa bovina, la peste porcina

clásica, la fiebre aftosa y, más recientemente, la influenza aviar con vacunas

producidas mediante deleción de genes, estrategias para diferenciar entre

animales vacunados e infectados (estrategias DIVA) y otros métodos similares.

Los autores también analizan la eficacia y los resultados obtenidos con las

vacunas marcadoras existentes y los equipos de diagnóstico asociados (que

deberán ser evaluados por un organismo independiente), así como la forma en

que las autoridades competentes las utilizarán. Asimismo, examinan

detalladamente las limitaciones y las ventajas de la administración de vacunas

marcadoras a la luz de la experiencia adquirida en la práctica. Pese a que

pueden limitar la velocidad y la importancia de la diseminación del virus y, por

consiguiente, reducir el número de animales sacrificados, las vacunas


contrôler et éradiquer la maladie d’Aujeszky, la rhinotrachéite infectieuse

bovine, la peste porcine classique, la fièvre aphteuse et plus récemment

l’influenza aviaire. Les auteurs examinent l’efficacité et les performances des

vaccins à marqueurs existants ainsi que des outils diagnostiques compagnons

(dont l’évaluation devrait être conduite par un organisme indépendant) ; ils

analysent également la manière dont ces outils sont utilisés par les autorités

compétentes. Ils étudient ensuite en détail les avantages et les limites de

l’utilisation des vaccins à marqueurs, à la lumière des expériences pratiques en

la matière. Bien que l’utilisation de ces vaccins ait pour effets de freiner et de

restreindre la dissémination virale, et partant de réduire le nombre d’animaux

abattus, elle n’a pas vocation à remplacer les mesures sanitaires. Les systèmes

de détection et d’alerte précoces et la mise en œuvre rapide de mesures

sanitaires, y compris l’abattage sanitaire, demeurent des mesures

incontournables de la lutte contre les maladies très contagieuses.

Mots-clés

Éradication – Excrétion virale – Fièvre aphteuse – Infection latente – Influenza aviaire –

Maladie d’Aujeszky – Mesure sanitaire – Outil diagnostique compagnon – Peste porcine

classique – Portage viral – Prophylaxie – Stratégie DIVA (différencier les animaux

infectés des animaux vaccinés) – Vaccin à marqueur – Vaccination.

Vacunas marcadoras y sus consecuencias

sobre el diagnóstico y medidas de profilaxis

marcadoras no pueden sustituir a las medidas sanitarias. Los sistemas de

detección y alerta rápidas y la aplicación inmediata de medidas de profilaxis,

incluido el sacrificio sanitario, siguen siendo decisivos para controlar las

enfermedades altamente contagiosas.

Palabras clave

Control – Enfermedad de Aujeszky – Equipo de diagnóstico asociado – Erradicación –

Estado portador de virus – Estrategia DIVA (diferenciación entre animales vacunados e

infectados) – Excreción viral – Fiebre aftosa – Infección latente – Influenza aviar –

Medida sanitaria – Peste porcina clásica – Vacuna marcadora – Vacunación.

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OIE standards for vaccines and future trends

S. Edwards

Veterinary Laboratories Agency, New Haw, Addlestone, Surrey KT15 3NB, United Kingdom

Professor Edwards is currently the President of the OIE Biological Standards Commission

Summary

The World Organisation for Animal Health (OIE), sets out international standards

for vaccines in the Manual of Diagnostic Tests and Vaccines for Terrestrial

Animals (mammals, birds and bees). The texts are drafted by experts then sent

for scientific peer review and for comment by all OIE Member Countries, thus

achieving a consensus at the point of adoption. Introductory chapters in the

Terrestrial Manual provide general principles of laboratory management and

vaccine production, and disease-specific chapters provide detailed standards

for vaccines for the OIE listed diseases. Issues that the OIE Biological Standards

Commission are currently addressing or will address in the near future include

the matching of vaccine strains to currently circulating infectious agents, the use

of companion diagnostic tests to differentiate infected from vaccinated animals,

the development of vaccine banks, and the application of DNA technology to

vaccine design and production.

Keywords

Biotechnology – Differentiating infected from vaccinated animals (DIVA) strategy –

International standard – Quality control – Safety – Vaccine – Vaccine bank.

IntroductionThe World Organisation for Animal Health (OIE) is anintergovernmental organisation of 169 Member Countries.The Organisation is mandated under the Sanitary andPhytosanitary Agreement of the World Trade Organizationto set standards that safeguard international trade inanimals and animal products. It has six primary objectives,which include the promotion of international solidarity inthe control of animal diseases, the publication of animalhealth standards, and provision of a better guarantee ofsafety in food of animal origin.

One of the OIE’s principal standard texts is the Manual ofDiagnostic Tests and Vaccines for Terrestrial Animals(mammals, birds and bees) (hereafter referred to as theTerrestrial Manual) (13), currently in its 5th edition. Thisarticle will explain the process by which the TerrestrialManual chapters are developed and approved, will outlinethe vaccine-related contents of the Terrestrial Manual, andwill seek to put these in the context of other national andsupra-national regulatory frameworks. The Terrestrial

Manual covers all the OIE listed diseases of terrestrialanimals together with a number of other diseases of animalor public health concern. It has become widely adopted asa key reference book for veterinary laboratories around theworld. Much of it is devoted to laboratory diagnostic tests,but this article will focus on the vaccine elements. There isa series of generic introductory chapters which give generalguidelines, including six with specific relevance to vaccines. The rest of the Terrestrial Manual consists of disease-specific chapters that provide generalbackground to:

a) the disease, its diagnosis and control

b) approved diagnostic techniques

c) requirements for vaccines and diagnostic biologicals.

A new updated edition of the Terrestrial Manualis published approximately every four years, but it hasbeen agreed by the International Committee of the OIEthat urgent updates, once approved by the Committee,may be incorporated in the online edition on the OIEwebsite (www.oie.int) without waiting for the next fullprinted edition.

The OIE Terrestrial Animal Health Code (14) also makesreference to use (or non-use) of vaccines, particularly inregard to the certification of animals or animal products forinternational trade, or to the surveillance and declarationof freedom from diseases or infections in specifiedpopulations. In such cases any vaccines should complywith the standards published in the Terrestrial Manual.

Development and approval of vaccine standardsThe OIE Terrestrial Manual is produced under the aegis ofthe Biological Standards Commission, supported by aneditorial team. The Commission appoints authors for eachchapter who are recognised as international scientificexperts on the particular disease or topic, and whoproduce a draft text, or modify and update an existing text.This is then submitted to scientific peer reviewers, and tothe delegates of all OIE Member Countries, for comment.Comments are collated, incorporated into the chapter ifstraightforward, or where necessary referred back to theCommission for a decision. Finally, texts are presented bythe President of the Commission to the OIE InternationalCommittee for approval and adoption. Thus, the OIE canrightly claim that the texts have consensus approval andsupport from its Member Countries, and that theytherefore represent valid international standards.

Chapters often make reference to new technologies underdevelopment, usually at the stage of ongoing research, butit should be clear that these are included for informationand are not yet adopted as formal standards. Conversely, insome cases older vaccine technologies may still have aplace in certain circumstances but may not be acceptablefor use in all Member Countries.

Generic chapters with relevancefor vaccine development

Tests for sterility and freedom from contamination

It is essential to show that all vaccines are free fromadventitious agents that may be accidentally introducedduring various stages of the production process. This is aparticular hazard with vaccines containing live attenuatedorganisms where a number of contaminants are recognisedas high risk, notably mycoplasmas and non-cytopathogenic viruses (particularly pestiviruses) in cellcultures used for viral vaccine production. The chapterprovides methodologies for detection of these and othercontaminants.

Seed lots used for production of the vaccine must beshown to be pure and free from contaminating strains. Inaddition, inactivated vaccines need to be shown to be fullyinactivated. Again, appropriate methodologies areprovided.

Safety in the veterinary microbiology laboratory

Laboratories (including vaccine manufacturing plants) areintrinsically hazardous environments. The chapter sets outthe principles of safe working practices taking into accountphysical and chemical hazards as well as the need toprotect staff from pathogenic micro-organisms. Althoughmany vaccines are derived from attenuated strains, this isnot always the case and comprehensive risk assessmentsare essential before any work is started. The standardscomplement, and do not replace, those established by theWorld Health Organization or national authorities. Inaddition, veterinary laboratories and vaccinemanufacturers need to avoid accidental release of animalpathogens, even where there is minimal risk to humans.An appendix to the chapter sets out the principles of suchbiocontainment specifying four containment levels, withthe highest (level 4) applying to highly contagiousorganisms such as foot and mouth disease (FMD) virus.

Principles of veterinary vaccine production

The regulatory framework for vaccine production iscomplex and varies between countries and regions.Specific reference is made in the chapter to EuropeanUnion Directive 2001/82/EC (as amended) (2), theEuropean Pharmacopoeia (3), and the Code of FederalRegulations in the United States of America (USA) (9). TheOIE is not a regulatory body, but sets out general principlesthat should be applied to any situation to ensure thatauthorised products are pure, safe, potent and effective.This provides a secure basis for the successful operation ofcontrol programmes for many animal diseases.

The chapter deals with questions of nomenclature, types ofvaccine, the requirements for a production plant, qualitymanagement, vaccine ingredients (including master seedsand other components), and the range of tests required todemonstrate safety, efficacy and stability, both duringmanufacture and in field use. Special reference is made tothe use of vaccines derived from recombinant DNAtechnology, where guidelines are still at the stage of activedevelopment, and this is considered in more detail in thechapter on biotechnology (see below).

International standards for vaccine banks

This new guideline, adopted in 2005 and available onlinefrom the OIE website, recognises the importance for


Member Countries of having rapid access to vaccines todeal with outbreaks of epizootic diseases. The manner inwhich such emergency vaccination is applied will varywith the disease, the epidemiological situation, and thedisease control policies of the country concerned. Vaccinebanks are designed to maintain stocks of vaccine or vaccineantigen for emergency use, often in countries wherevaccination for the disease is not normally practised. Thebanks may be national or held on behalf of multi-countryconsortia. In the latter case clear legal agreements arerequired concerning access by individual countries.Arrangements need to take account of regulatory controlsas well as lead time for reconstitution and filling to finalproduct. The vaccine bank and its management should bean integral part of a country’s contingency plan for controlof exotic diseases. Key decisions need to be madeconcerning the number of doses to be stored and thestrains of organism to be included in the bank –particularly for antigenically variable pathogens such asFMD virus, where the constituents of the bank may needto be regularly reviewed and updated to match currentlycirculating field strains. Although there may be specialregulatory provisions for the use of emergency vaccinationin Member Countries, the vaccine bank is not exempt fromthe general principles underlying safety and efficacy, andthe facility must still comply with the quality principles ofGood Manufacturing Practice.

Biotechnology in vaccine development

A number of biotechnological approaches are now wellestablished in vaccinology and authorised products arealready in use for disease control in the field. Goodexamples are the deletion of genes from bacteria or virusesto reduce the virulence (e.g. Aro mutants of Salmonella spp.[4]), in contrast to traditional methods of attenuationthrough multiple passage in culture. The chapter providesseveral examples where such gene-deleted vaccines can beused in conjunction with a companion diagnostic test todifferentiate infected from vaccinated animals (the DIVAstrategy), e.g. Aujeszky’s disease (10) and infectious bovinerhinotracheitis. Other technologies, which also offer theopportunity for DIVA strategies, include subunit viralvaccines, based on individual immunogenic proteinsexpressed in heterologous systems such as baculovirus orpoxvirus (e.g. E2 protein of classical swine fever virus[14]). The DIVA approach allows the eradication of adisease in the presence of a vaccination strategy for diseasecontrol (11).

Vaccines have also been developed in which a live virusvector is used to express an immunologically relevantprotein of the pathogenic organism, giving the advantagesof live virus vaccines (replication in the host leading tobetter immune responses) without the risk of reversion to

virulence. A classic example is the vaccinia-vectored rabiesvaccine that has been used successfully for disease controlin wildlife (7). More recently, a number of vaccines basedon avian pox viruses have been developed (8). When usedin mammalian hosts these express the foreign vectoredgene and stimulate protective immunity withoutreplicating to produce progeny virus.

Finally, the role of DNA vaccines is considered. Althoughnot as yet a fully developed technology it showsconsiderable potential (6) and the current state of scientificdevelopment is described in the chapter.

The role of official bodies in vaccine regulation

This chapter (online version updated in 2005) outlines insome detail the regulatory procedures in the three regionsthat have made most progress in this field, namely Japan,the European Union, and the USA. In addition, the role ofthe appropriate pharmacopoeias is discussed, particularlythe European Pharmacopoeia (3) (which has 35 signatorymember states, as well as a further 17 with observerstatus). The procedural differences are described betweenthe American and European systems, together with effortsbeing made to harmonise these with each other, and withregulations of other countries and regions. TheInternational Cooperation on Harmonisation of TechnicalRequirements for Registration of Veterinary MedicinalProducts (abbreviated to VICH) is a trilateral programme ofthe EU, Japan and the USA which has an ongoingcommitment to develop harmonised technical standardsfor vaccine production. Unfortunately progress to date hasbeen rather slow.

Disease-specific chapters

Vaccination as a disease control method is not applicable inall cases, but where there are useful vaccines available eachdisease-specific chapter provides a basic standard for theirmanufacture and usage. The standards follow a consistentformat of:

– seed management

– method of manufacture

– in-process control

– batch control

– tests on the final product.

Where there is more than one vaccine type available, anintroductory account is given to enable users to makeinformed choices on the preferred approach. It is not


possible in this short article to go into detail for all thelisted diseases, for which reference should be made to theTerrestrial Manual. We shall briefly examine two specificaspects of particular interest, namely, vaccine matchingtests for FMD and DIVA strategies.

Foot and mouth disease: vaccine matching tests

Vaccinal immunity to FMD virus is serotype-specific, buteven within serotypes complete cross-protection betweendifferent isolates may not occur. A new text, adopted inMay 2006 by the OIE International Committee, presentsfor the first time a detailed explanation of how to selectcirculating field viruses, and how to evaluate these usingantisera specific to different vaccine strains for the best fitfor cross-protection. Tests used may be based oncomplement fixation, enzyme-linked immunosorbentassay, or virus neutralisation technologies.

Strategies for differentiating infected from vaccinated animals

There are a number of diseases for which a DIVA approachmay be used, allowing continued vaccination while stillbeing able to detect infected animals through serologicalresponses to proteins that are absent from the vaccine. Sofar this has been limited to certain virus infections, but theprinciple could be applied more widely. The details of theDIVA approach vary with the disease. Thus, for FMD, thevaccines used are conventional inactivated viral vaccines,but highly purified during manufacture so that they lackimmunologically significant levels of non-structuralproteins (NSP) (5). Animals naturally infected with FMDvirus do develop antibodies to NSP, even if alreadyvaccinated, so an NSP-specific antibody test can be used ina DIVA strategy. This has the additional advantage of notbeing serotype-specific.

In the case of avian influenza, use can be made of naturallyoccurring strains for vaccine manufacture where theneuraminidase type is different from the circulating fieldvirus, taking advantage of the fact that the main protectiveimmune response is to the haemagglutinin protein. Thus,neuraminidase inhibition serological tests provide a meansof detecting field infection in birds that have beenvaccinated against a haemagglutinin type homologous tothe field virus (1).

Other examples of DIVA applications, as mentioned aboveinclude the use of gene-deleted vaccines for herpesviruses(Aujeszky’s disease, infectious bovine rhinotracheitis), and

recombinant vaccines expressing a single immunogenicviral protein (classical swine fever E2 glycoprotein).

Future trends/concludingremarksThe need for new and improved vaccines will continue inthe future because the demand for livestock and livestockproducts is expected to grow enormously in the next fiftyyears, particularly in developing countries. This will lead tomore disease problems and emerging diseases. Thedemand for cheap, reliable vaccines will increase andgeneral guidelines are essential, especially for thedeveloping countries.

There is a pressing need to encourage efforts towardsinternational harmonisation, including technicalprocedures related to quality control, the evaluation ofsafety and efficacy of vaccines, and the regulatory protocolsused to authorise products in different countries. In thisrespect the VICH initiative is to be welcomed. Meanwhile,the continual improvement of the chapters in the OIETerrestrial Manual will provide internationally recognisedstandards that are of particular value to those countrieswhich do not as yet have fully formed regulatory processes.

Vaccine banks are expensive to set up and maintain, butthis must be set against the enormous potential costs ofnon-vaccination strategies in the face of increasing globalspread of diseases. Agreed standards for the maintenanceand exploitation of such banks are therefore essential.

Advances in biotechnology, immunology and proteomicswill continue to generate novel approaches to vaccinedesign. It is essential that robust standards are in place andare applied to ensure that new products are adequatelyevaluated both for their safety and efficacy for the animaland the consumer, and for any environmental impacts thatmay ensue.

AcknowledgementsI am grateful to Christianne Bruschke for her insight andadvice in the preparation of this article.



Normes de l’OIE relatives aux vaccins et tendances pour l’avenir

S. Edwards

Résumé

Les normes internationales prescrites par l’Organisation mondiale de la santé

animale (OIE) en matière de vaccins sont décrites dans le Manuel des tests de

diagnostic et des vaccins pour les animaux terrestres (mammifères, oiseaux et

abeilles). Ces normes sont préparées par des experts, soumises à une évaluation

collégiale puis diffusées auprès des Pays Membres de l’OIE afin de recueillir

leurs commentaires ; au moment d’être adoptées, elles sont donc le fruit d’un

large consensus. Les premiers chapitres du Manuel terrestre exposent les

principes généraux régissant la gestion des laboratoires et la production de

vaccins, tandis que les chapitres sur les maladies décrivent en détail les normes

relatives aux vaccins pour chaque maladie figurant sur la liste de l’OIE. Plusieurs

questions d’intérêt immédiat ou futur sont actuellement examinées par la

Commission des normes biologiques de l’OIE : l’adéquation des souches

vaccinales avec les souches pathogènes en circulation ; le recours à des tests

diagnostiques compagnons, permettant de distinguer les animaux infectés des

animaux vaccinés ; la création de banques de vaccins et les technologies de

l’ADN applicables au développement et à la production de vaccins.

Mots-clés

Banque de vaccins – Biotechnologie – Contrôle de qualité – Norme internationale –

Sécurité – Stratégie pour différencier les animaux infectés des animaux vaccinés (DIVA)

– Vaccin.

Normas de la OIE sobre vacunas y tendencias de cara al futuro

S. Edwards

Resumen

La Organización Internacional de Sanidad Animal (OIE) fija normas

internacionales sobre vacunas en su Manual de pruebas de diagnóstico y

vacunas para los animales terrestres (mamíferos, aves y abejas). Tras una

primera fase de redacción, a cargo de especialistas, los textos se someten al

examen de otros expertos de igual nivel y a las observaciones que puedan

formular todos los Países Miembros de la OIE, proceso que culmina con un

consenso en el momento de la aprobación. Los capítulos introductorios del

Manual terrestre sientan principios generales sobre procedimientos de

laboratorio y fabricación de vacunas, mientras que en los capítulos siguientes,

dedicado cada uno a una patología, se fijan normas detalladas sobre las

vacunas contra las enfermedades inscritas en la lista de la OIE. Entre los temas

de los que se ocupa o va a ocuparse la Comisión de Normas Biológicas de la OIE

figuran la adecuación de las cepas vacunales a los agentes infecciosos

actualmente en circulación, el uso de pruebas de diagnóstico complementarias

para distinguir entre animales infectados y vacunados, la creación de bancos de

vacunas o la aplicación de la tecnología del ADN a la concepción y fabricación

de vacunas.

Palabras clave

Banco de vacunas – Biotecnología – Control de calidad – Estrategia de discriminación

entre animales infectados y vacunados (DIVA) – Norma internacional – Seguridad –

Vacuna.

References1. Capua I., Cattoli G., Marangon S., Bortolotti L. & Ortali G.

(2002). – Strategies for the control of avian influenza in Italy.Vet. Rec., 150, 223.

2. Commission of the European Communities (2001). –Directive 2001/82/EC of the European Parliament and of the Council of 6 November 2001 on the Community coderelating to veterinary medicinal products. Off. J. Eur.Communities, L 311, 1-66.

3. Council of Europe (COE) European Directorate for theQuality of Medicines (EDQM) (2005). – Europeanpharmacopoeia, 5th Ed. COE, Strasbourg.

4. Jones P.W., Dougan G., Howard C., Mackenzie N., Collins P.& Chatfield S.N. (1991). – Oral vaccination of calves againstexperimental salmonellosis using a double aro mutant of Salmonella typhimurium. Vaccine, 9, 29-34.

5. Mackay D.K.J., Forsyth M.A., Davies P.R., Berlinzani A.,Belsham G.J., Flint M. & Ryan M.D. (1997). – Differentiatinginfection from vaccination in foot-and-mouth disease using apanel of recombinant, non-structural proteins in ELISA.Vaccine, 16, 446-459.

6. Nobiron I., Thompson I., Brownlie J. & Collins M.E. (2003).– DNA vaccination against bovine viral diarrhoea virusinduces humoral and cellular responses in cattle with evidence for protection against viral challenge. Vaccine,21, 2091-2101.

7. Pastoret P.-P. & Brochier B. (1996). – The development anduse of vaccinia-rabies recombinant oral vaccine for thecontrol of wildlife rabies: a link between Jenner and Pasteur.Epidemiol. Infect., 116, 235-240.

8. Taylor J., Trimarchi C., Weinberg R., Languet B., Guillemin F.,Desmettre P. & Paoletti E. (1991). – Efficacy studies on acanary pox-rabies recombinant virus. Vaccine, 9, 190-193.

9. United States Department of Agriculture (USDA) (2001). –Code of Federal Regulations, Title 9, Animals and animalproducts, Part 113, Standard requirements. US GovernmentPrinting Office, Washington, DC, USA.

10. Van Oirschot J.T., Terpstra C., Moormann R.J.M., Berns A.J.M. & Gielkens A.L.J. (1990). – Safety of anAujeszky’s disease vaccine based on deletion mutant strain783 which does not express thymidine kinase andglycoprotein I. Vet. Rec., 127, 443-446.

11. Van Oirschot J.T., Kaashoek M.J. & Rijsewijk F.A.M. (1996).– Advances in the development and evaluation of bovineherpesvirus 1 vaccines. Vet. Microbiol., 53, 43-54.

12. Van Rijn P.A., Van Gennip H.G. & Moormann R.J. (1999). –An experimental marker vaccine and accompanyingserological diagnostic test both based on envelopeglycoprotein E2 of classical swine fever virus (CSFV). Vaccine,17, 433-440.

13. World Organisation for Animal Health (OIE) (2004). –Manual of Diagnostic Tests and Vaccines for TerrestrialAnimals, 5th Ed. OIE, Paris.

14. World Organisation for Animal Health (OIE) (2006). –Terrestrial Animal Health Code, 15th Ed. OIE, Paris.



Regulatory requirements

for vaccine authorisation

P.G.H. Jones (1), G. Cowan (2), M. Gravendyck (3), T. Nagata (4), S. Robinson (5) & M. Waits (6)

(1) International Federation for Animal Health, rue Defacqz, 1, 1000 Brussels, Belgium

(2) Pfizer Limited, Ramsgate Road, Sandwich, Kent, CT13 9NJ, United Kingdom

(3) Intervet International BV, Wim de Korverstraat 35, PO Box 31, 5830 AA Boxmeer, the Netherlands

(4) Merial Japan Ltd., Sanno Grand Building, 2-14-2 Nagata-cho, Chiyoda-ku, Tokyo 100-0014, Japan

(5) Fort Dodge Animal Health, Asia Pacific Regional Technical Office, 1 Maitland Place, Baulkham Hills, NSW

2153, Australia

(6) Merial Ltd., 115 Transtech Drive, Athens, GA 30601, United States of America

Summary

Vaccines are one of the most important tools available in the prevention and

control of diseases in animals. It is therefore of the utmost importance that when

vaccines are used, such use should meet with the requirements of the World

Organisation for Animal Health Terrestrial Animal Health Code and must be

authorised by the recognised licensing body in the country/region where the

vaccines are to be used, in accordance with the three key criteria of quality,

safety and efficacy.

This article provides a comprehensive and comparative description of

the regulatory requirements in place for veterinary vaccines in major regions

of the world, highlighting the similarities and pointing out also where there are

differences. Recent advances in harmonisation of such testing requirements

achieved through the International Cooperation on Harmonisation of Technical

Requirements for Registration of Veterinary Medicinal Products (VICH) are also

described. The contents will provide a valuable guide to those engaged in the

research and development of vaccines globally, and reassure those involved in

the prevention and control of animal diseases that veterinary vaccines, when

fully authorised and used according to the label instructions, are safe and

efficacious.

Keywords

Efficacy – Harmonisation – International Cooperation on Harmonisation of Technical

Requirements for Registration of Veterinary Medicinal Products (VICH) – Quality –

Regulatory requirements – Safety – Veterinary vaccine.

IntroductionVaccines for animals, like all other veterinary medicines,have to be licensed by the relevant authorities charged withthat responsibility in the country or region where theproducts are to be marketed. The authorisation process hasto ensure that the medicinal product is of adequate qualityand purity, that it is safe and that it works in the targetspecies as claimed, for the indication/treatment for whichit is intended.

Whilst society rightly demands that medicines, includingvaccines, are licensed according to very high standards, theregulatory environment should not be so risk-averse in thedemands made on sponsors of new products thatinnovation and investment in research and developmentare stifled, and the availability of adequate veterinarymedicines compromised.

Veterinary vaccines, like those produced for human use,are therefore authorised according to high standards of

quality, safety and efficacy (taking account of therisk/benefit balance for each product under consideration)and these three major criteria are mostly defined in asimilar way in the major markets around the world.However, there is variation between different countries,such that regulatory dossiers have often to be tailored fordifferent markets. This adds to the already considerableexpense which companies incur when researching anddeveloping a new medicine, which can take over a decadeand cost as much as 50 million euros.

These high costs are often the cause of additional problemsin the veterinary sector, which differs considerably fromthe human medicine sector. Because the investmentneeded to bring new products to the market place is solarge, vaccines for so-called minor species, where thepotential market size is small (e.g. rabbits, goats and somespecies of poultry) rarely get developed, because the returnon investment is not attractive enough for the animalhealth companies involved in marketing them. As a resultmany vaccines needed for use in minor species are just notavailable and licensed vaccines for one species may not besuitable for use in another species, which can result in apotential conflict for practising veterinarians in their dutyof care and welfare to their patients.

During the development of a new vaccine the marketingauthorisation holder must subject the vaccine to varioustests defined in the legislation and guidelines, and these aresometimes revised. If such changes arise when a newproduct is well into its development phase, theconsequences can be grave, with further costs beingincurred to generate additional data to satisfy the newlyimposed changes in requirements.

Such unpredictability certainly drains reserves forinvesting in new products and curbs investment in newtechnology and innovation as well. Fortunately, regulatoryauthorities are now more aware of such constraints, andare prepared to collaborate with the animal health industryto set more realistic requirements that facilitate thedevelopment of new medicines, whilst at the same timeremoving hurdles that can delay the time it takes to bringbadly needed new products to market.

Procedures for licensingveterinary vaccinesThis section describes the procedures which potentialapplicants wishing to license vaccines in the major animalhealth markets around the world need to follow. Theconditions under which the different authorities willconsider applications for licensing, and the requirementswhich have to be satisfied are also covered to a degree that

will provide the reader with a good understanding of therigorous regulatory systems in place to ensure that onlyhigh quality, safe and efficacious vaccines come onto themarket place.

Safety is of course of paramount importance. Thedetermination of safety is fundamentally a determinationthat the benefits of the product outweigh any potentialrisks, not only to the target species being vaccinated, butalso to the user/administrator of the vaccine, theenvironment, and in the case of animals from which foodis derived, the consumer as well.

The major regulatory authorities essentially have similarguidance on how to apply for a licence and a synopsis ofthe actual data required with reference to the differencesbetween the various regions is provided in the next section.

Applications are generally submitted to the authority incharge of licensing medicines and these can be separateveterinary regulatory departments within the Ministry ofAgriculture, stand-alone agencies within governments oreven parts of a joint regulatory department withresponsibility for human medicines as well. The applicant,normally a pharmaceutical company, has to be legallyestablished in the country/region concerned andconstituted under civil or commercial law to ensure thatobligations for compliance with the legal-regulatorypharmaceutical framework are fully adhered to.

What follows is a summary of the systems in place, theauthorities responsible and the type of informationrequired.

Japan

Veterinary drugs are under the control of the Ministry ofAgriculture, Forestry and Fisheries (MAFF), which issuesthe licence/market approval for each vaccine following areview of the application dossier by various committeescharged with assessment of the data. The standardapproval time for a new vaccine is up to one year,excluding any time required for responding to requestsfrom the Ministry for additional data from the applicant.The approval of a conventional vaccine listed as amonograph in the Standards of Veterinary Vaccines forNational Assay does not require renewal, whereas theapproval of a vaccine containing a new class of antigen ornew combination of antigens requires renewal after sixyears following the initial approval.

United States of America

Applications for licensing have to be submitted to theCenter for Veterinary Biologics (CVB) which is part of


Veterinary Services (VS), a division of the Animal Healthand Plant Inspection Service (APHIS) of the United StatesDepartment of Agriculture (USDA). The agency allowsphased filing, which allows for the submission of resultsfrom studies as they become available instead of having toassemble a complete dossier for submission. Documentsneeded for phased filing are described in VeterinaryServices Memorandum No. 800.50 and consist of threemajor packages: Application for Product License,Supporting Data for Product License Application, andRequests to Conduct Field Studies. As stated in thismemorandum, the applicants are encouraged to interactwith CVB personnel as necessary, to facilitate submissions.The licence has no expiration date and does not need to berenewed as long as product is produced on a regular basis.The CVB supports a serial release system; each serialproduced is submitted to the CVB for review, possibletesting and official release.

European Union

Potential applicants have a choice of routes toauthorisation of vaccines in the European Union (EU). Ifthe vaccine is derived from biotechnology then theapplication must be filed with the European MedicinesAgency (EMEA) in London, through the so-called‘centralised procedure’ and the dossier is assessed by theCommittee for Medicinal Products for Veterinary Use(CVMP) within a legislative time frame of 210 days,excluding the time taken for companies to provideadditional data to the Committee if requested to do so. Ifthe Committee is in favour of the application it issues apositive opinion which is then transferred into aCommunity marketing authorisation by the EuropeanCommission in Brussels, giving the company thecommercial advantage of allowing it to market the vaccinein all 27 member states of the EU. This route to licensingis also open to non-biotech vaccines if they are innovativeand/or can be shown to have particular advantages foranimal health. Shortly after the Community Authorisationis published in the Official Journal of the EU, the EMEApublishes on its website a European Public AssessmentReport (EPAR) which provides a detailed summary of theCVMP assessment, excluding proprietary informationabout the product considered to be confidential. EPARs ofall vaccines authorised through this procedure are to befound on the EMEA website (www.emea.europa.eu).

Alternatively, if the vaccine is not derived frombiotechnology or is innovative, but the applicant onlywishes to market the product in a few of the 27 EUmember states, then the submission of the dossier can bemade through a national procedure followed by the mutualrecognition of this approval by other EU member states orthrough the new decentralised procedure, in which theapplicant selects the member states in which they wish to

market the product and these are all included in theassessment procedure from the outset, with one regulatoryagency acting as the reference member state that leads theprocedure. With mutual recognition procedures thedossier is submitted to the regulatory authority of onemember state (the reference member state), whoundertakes the assessment, and once approved, theauthorisation to market is mutually recognised by the othermember states where the company has filed the dossier(the concerned member states). Public Assessment Reportsfor vaccines authorised through this route are also soon tobe made public.

Australia

All vaccines must be registered by the Australian Pesticidesand Veterinary Medicines Authority (APVMA) inaccordance with the Agricultural and Veterinary ChemicalsAct 1994 and the Agricultural and Veterinary ChemicalsCode Act 1994 and other supporting legislation. OnceAPVMA registration is granted, state by state registration isnot required.

Presentation of dossiersDetails of the responsible authorities and the appropriatelegislation for authorisation of vaccines in the variousmajor markets are provided in Table I.

With all these authorities, the dossier is presented andsubmitted according to the local requirements. However,the submission is generally required to be formatted in astructured manner and must include an administrative partwhich will include detailed information on the applicantcompany, the provision of samples if required, informationon the manufacturing site, evidence of conformance toGood Manufacturing Practice (GMP), and details ofmarketing authorisations/licences granted elsewhere.Details on the product itself and its characteristics areincluded in this section, as is information on the proposedpackaging and labelling of the vaccine.

The main part of the dossier is the technical sectionconsisting of manufacture and control, followed by safety,preclinical and clinical documentation, respectively.

Post-authorisation requirementsRegulation of vaccines does not, however, end with theissuing of a marketing authorisation. The post-authorisation phase is just as important in the product’s lifecycle as that prior to its introduction: the requirement tomonitor for any potential adverse reaction to a vaccine


once licensed is an integral part of the regulatory systemfor most authorities.

In most countries, therefore, the licence holder is requiredto have in place an appropriate means of monitoring thevaccine in the field, i.e. they must carry outpharmacovigilance/vaccinovigilance. With marketing anduse of a product in large numbers of animals under normalfield conditions, valuable information about the safetyprofile of the product is gathered. This post-marketingmonitoring assists in the detection of adverse events thatoccur infrequently in large populations and would notordinarily be recognised in pre-authorisation safetystudies. If any potential safety problems are detected, theproduct sponsor and the regulatory authority collaborateon the appropriate measures to address identified issues.For this purpose the regulatory systems in force have veryspecific guidelines enshrined in law as to the obligationsfor reporting adverse drug reactions, the content andtiming of such reports, and the actions incumbent on thelicence holder in following up with the appropriateinvestigations.

Technical data requirementsWhat follows is a detailed presentation of the testingrequirements in the major regions of the world forauthorising vaccines, which enables a comparison to bemade of the differences which may exist, and which areextremely important for companies who may be intendingto register and commercialise products on a global basis.Details of the registration requirements are provided forthe EU, the United States of America (USA), Japan andAustralia, thus providing a global overview of the

framework of the systems for authorising vaccines indifferent parts of the world.

It is important first of all however to draw attention toefforts that have been ongoing for a number of years toharmonise such requirements. The InternationalCooperation on Harmonisation of Technical Requirementsfor Registration of Veterinary Medicinal Products (VICH)was officially launched in April 1996. This is a trilateralprogramme between Japan, the USA and the EU aimed atestablishing harmonised technical requirements whichmeet quality, safety and efficacy standards, minimising theuse of test animals and reducing the costs of productdevelopment. A number of guidelines have beenestablished or are in the process of being established toharmonise the requirements for biologicals, and details ofthese can be found on the VICH website(www.vichsec.org). Australia, Canada and New Zealand areobservers to VICH and also implement the adoptedguidelines in their regulatory systems.

Requirements for the registration of veterinaryvaccines in the European Union

Categories of veterinary vaccines

Vaccines exist against viral, bacterial, fungal or parasiticinfections. These can be based on live, attenuated, or inactivated agents. Within these categories completecausative agents (whole cell vaccines) or parts of an agent(subunit or vector vaccines) may be used to obtainprotection. Because the vast majority of existing vaccines


Table I

Summary details of the responsible bodies and the legislation in place for authorising vaccines

Country Department responsible Pharmaceutical legislation

Japan National Veterinary Assay Laboratory, Ministry Pharmaceutical Affairs Law No. 145 Series of 1960

of Agriculture, Forestry and Fisheries, Tokyo

United States of America Center for Veterinary Biologics, Animal Health and Plant Title 21 of the United States Code (Nos 151-159), with implementing

Inspection Service, United States Department of Agriculture regulations in Title 9 of the Code of Federal Regulations (Nos 101-122)

European Union Innovative and biotechnology vaccines: European Regulation No. 726/2004 of the European Parliament

Medicines Agency, Unit for Veterinary Medicines, London, and of the Council

United Kingdom

Conventional vaccines: European Union Member State Directive 2004/28/EC of the European Parliament and of the Council

Competent Authorities*

Australia Australian Pesticides and Veterinary Medicines Authority Agricultural and Veterinary Chemicals Act 1994 and the Agricultural

and Veterinary Chemicals Code Act 1994

* see http://www.hevra.org/directory.asp

are used against viral or bacterial infections this article willmainly focus on the requirements for live and inactivatedvaccines of these types.

Basic registration requirements

Although regulations may differ, in general, all authoritiesaim at licensing only those products that meet a number ofbasic requirements. Only vaccines whose quality, safetyand efficacy have been proven obtain a marketingauthorisation in the EU. A vaccine licence is initially issuedwith a five-year validity. After re-evaluation of therisk/benefit balance the marketing authorisation isrenewed and is thereafter valid for an unlimited period oftime. Apart from direct EU law, companies should also takeinto account other legislation that is applicable in Europe,e.g. the European Pharmacopoeia (Ph. Eur.). In the Ph.Eur. general requirements as well as specific tests forstarting materials or the final product (vaccinemonographs) are laid down.

The current EU criteria which veterinary vaccines mustmeet are outlined below.

Quality

ManufactureSince licensing of veterinary vaccines was formallyintroduced in the EU in 1981 it has been a requirementthat both the active ingredient (antigen) and the finishedproduct (vaccine) must be manufactured according toGMP. Even before that time, some national regulatoryagencies already insisted on GMP for the manufacture ofveterinary vaccines.

In addition to a marketing authorisation for each countryin which the product is to be marketed, a manufacturinglicence must be obtained for each production facility wherethe vaccine (or part thereof) is being produced. Data mustbe presented to show that the manufacturer is able toproduce the vaccine in a consistent manner.

Regular internal and external audits aim at surveying thequality control procedures in place. Moreover, a vaccineproducer must employ at least one qualified person who is,without prejudice to his relationship with the holder of themanufacturing authorisation, personally responsible forrelease of vaccine onto the market.

The quality of starting materials used for production,whether bought from a commercial supplier or producedin-house, must be evidenced. In the case of ingredientspurchased from external suppliers, the commercialsupplier has his own quality assurance system. In addition,controls on incoming-goods are performed by the vaccinemanufacturer (e.g. growth promotion assays for serumbatches used to cultivate certain vaccine strains) to further

guarantee the quality of the material. The vaccinemanufacturer must declare a specification for each startingmaterial and ensure that each batch purchased meets theacceptance limits of the specification. Many startingmaterials are listed as monographs in the Ph. Eur. Eventhese must be tested to ensure compliance with the currentmonograph. Additionally, requirements exist for startingmaterials of biological origin which are commonly used forvaccine production (e.g. exclusion of extraneous agents).

Seed stocks of the vaccine strain are laid down in a seed lotsystem, making passages from the master seed to establisha bank of working seed from which all production batchesare produced. The history of the isolation and previouspassages of the initial master seed must be known in orderto minimise the risk of transmission of spongiformencephalopathies (TSE).

TestingPurityA veterinary medicinal product must be sterile, i.e. freefrom any contamination with live microbiological agents.In the specific case of live vaccines the product should notcontain live microbiological agents other than the vaccinestrain(s). In order to achieve this, the master seed stockfrom which all subsequent vaccine batches will derivemust be absolutely free from extraneous agents.

For virus vaccines this means freedom from contaminatingbacteria, fungi, Mycoplasma species, and extraneousviruses; for bacterial vaccines it means freedom fromcontaminating bacteria and fungi. The expression used todetermine freedom from contamination for bacterialvaccines is ‘purity’. To confirm the absence of extraneousagents in virus vaccines, validated assays must be used, i.e.spiking of the seed virus with a series of extraneous agentsshould reveal positive test results.

IdentityIn addition to purity, the vaccine strain must be tested toensure it is identified as the correct strain. Identification ispursued beyond the strain and species to subtypes orserotypes as appropriate.

In-process and finished product testingTo ensure that each batch of a commercial vaccine isequivalent in quality and will therefore be safe andefficacious, the manufacturer must register all relevant in-process tests as well as tests to be performed on thefinished product, giving limits of acceptance that must bemet before the batch can be released for sale. Once thesetest methods and limits have been approved by theregulatory agencies, they become mandatory tests forplacing the vaccine on the market. The type of testsperformed may include:

– sterility/purity tests for absence of contamination


– antigen quantification tests (e.g. titre, cell count, opticaldensity, enzyme-linked immunosorbent assay [ELISA],etc.)

– tests for complete inactivation (inactivated vaccinesonly)

– physico-chemical tests, e.g. pH, viscosity of emulsion,quantity of residual inactivant, etc. (mainly valid forinactivated vaccines)

– adjuvant content tests, if an adjuvant is included in theformulation

– tests to determine the titre (live vaccines) or potency(inactivated vaccines) of finished product (see the sectionon ‘Potency’ below)

– tests to verify the safety of the product in the targetspecies.

Each batch of vaccine must be tested for absence of localand systemic effects in animals of the target species usingan overdose (2 3 for inactivated vaccines and 10 3 for livevaccines) administered by a route recommended on thelabel. The marketing authorisation holder may apply for avariation to the licence to withdraw this test followingsatisfactory results from at least ten batches and satisfactorypharmacovigilance reporting.

In addition, the manufacturer must prove that the qualityof the vaccine is guaranteed until the end of its shelf life.To demonstrate this, stability testing must be performed onat least three batches of vaccine in the final container. Thevaccine must be tested at regular intervals throughout theproposed shelf life. If a preservative is included in thevaccine (multidose containers only), its effectivenessduring the shelf life must be tested using a methoddescribed in the Ph. Eur.

Safety

Clearly, the product must be safe for the target animal, butit must also be documented that the product does not posea danger to humans or to other animals that may come intocontact with the product, or to the environment.Experimental data obtained with batches with the highestpotency or titre (see below) must be generated in speciallydesigned experiments, i.e. in accordance with EuropeanGood Laboratory Practice (GLP) standards.

In addition to the safety of a single dose, the safety of anoverdose and repeated doses of the vaccine must beshown. The rationale for demonstrating the safety of arepeated dose is because some vaccines, especiallyinactivated ones, have a primary vaccination courseconsisting of two doses, followed by a booster dose six ortwelve months later. For a vaccine with thisrecommendation, demonstration of the safety of repeated

administration of the product will consist of monitoringthe safety (e.g. injection site reaction, clinical symptoms)following three administrations of the vaccine withappropriate intervals between each administration.

There are additional special requirements for live vaccines.A live vaccine strain must be stable, i.e. should not revertto virulence during consecutive passages. Depending onthe agent, recombination or genomic reassortment needsto be evaluated. In general, vaccine is produced within alimited number of passages from the master seed stock.Usually this is limited to five passages for virus vaccines,however, there is no limit for bacterial vaccines. The safetyof the vaccine strain at the lowest passage number is shownin animal studies using the most sensitive targetanimal/species. Issues such as the spread of the vaccinestrain and dissemination in the vaccinated animal need tobe taken into account where appropriate. In addition,studies on the immunological functions may have to becarried out where the vaccine might adversely affect theimmune response.

If the vaccine is intended for administration to pregnantanimals, safety during pregnancy must be shown using abatch of vaccine at its highest potency or titre. It must bedemonstrated that vaccination has no adverse effect on thereproductive performance of the target animal.

Depending on the starting materials used formanufacturing the vaccines, studies may need to be carriedout on possible residues if they are considered to bepresent at levels having pharmacological activity. Negativeeffects on the environment must also be assessed.

Additional requirements have to be met for vaccinescontaining genetically modified organisms.

Efficacy

Data must be provided that support the efficacy claims. Inother words: a product must be able to do what is claimedon the label (e.g. reduce virus shedding, control clinicalsigns, etc.). Preferably, these data are obtained from fieldtrials performed under Good Clinical Practice-veterinary(GCPv) conditions and from laboratory studies in which, ifpossible, validated experimental challenge models areused. Data showing efficacy from laboratory studies mustbe provided using batches with the lowest potency or titre(see below).

Potency

The manufacturer must provide data that guarantees theimmunising capability and thereby protective effect of aproduct over the entire shelf life. This is a major hurdle inthe development of inactivated vaccines. Confirmation ofthe protective effect of a specific immunogen is usuallyestablished by vaccination-challenge experiments.


Such experiments are preferably not used as routine batchpotency tests as these involve animal experimentation andare normally of several weeks duration. An alternative testshould ideally be developed which is carried out on eachbatch of finished vaccine and has predictive value as to theefficacy of that particular batch. As the efficacy of thevaccine batch has to be guaranteed over its entire shelf lifethe batch potency test must provide assurance that thevaccine will remain potent throughout its shelf life. Thisassurance is provided by testing the vaccine’s stability overthe period of the shelf life plus an additional three monthsbeyond for a minimum of three batches. The pass level forbatch release is set at the minimum level that was shown tobe efficacious in the target animal. If the protectivemechanism of immunity against a specific pathogen is notknown, it may take years before an accurate potency testcan be developed.

Special requirements

Registration of the label claim

In the EU, each marketing authorisation is granted with anapproved Summary of Product Characteristics (SPC). Thisdocument reflects the results of the supportive dataprovided in the registration dossier. It includes adescription of the composition of the vaccine, the targetspecies, the route of administration, the supportedvaccination schedule, the claims, any contra-indications oradverse effects that might be seen, the shelf life and adescription of the vaccine containers and storageconditions. If the marketing authorisation holder wishes tochange any of the statements made on the SPC, this can beachieved by varying the licence with the appropriatesupporting data.

Target animalThe animal species for which the product is intended mustbe specified and it should be clearly stated if the vaccine isdesigned for use in a specific category of animal, e.g.broiler chickens not breeder chickens. The suitability ofthe product for use in pregnant animals should also bestated. An important factor may be the presence ofmaternal immunity in young animals. If this may affect theinduction and onset of vaccine-induced immunity then itmust be studied. Results may prompt the manufacturer torecommend not vaccinating animals below a certain age.

Route of administrationSome products can be administered through differentroutes, e.g. oral application or injection. For each of theseroutes of administration safety and efficacy experimentsmust be performed to support the claims made. Theseclaims may differ depending on the route ofadministration, and this must be clearly stated in thedossier and on the label and leaflet (known as the ‘circular’in US regulations).

Onset and duration of immunityApart from the information requirements imposed byregulatory authorities, most of the label informationrelating to the onset and duration of immunity is includedon the label because of market demand. All claims must bedocumented and supported, either by existing literature orby experimental data. This may take years of research,particularly if, for instance, one claims that a product has ashelf life of three years. Specific efficacy claims must alsobe supported by data. If, for example, the label claims thatthe duration of immunity is one year and that a yearlyvaccination will sustain this level of immunity, data mustbe provided that show that one year after the primaryvaccination course, animals are significantly protected (insome cases by experimental challenge infection) and alsothat animals that receive a single booster vaccination oneyear after initial vaccination are still protected one yearlater. This involves more than two years ofexperimentation.

CompatibilityIf the label claims that the vaccination may be carried outwithin two weeks of vaccination with another product(concurrent use) then this must also be documented withsupportive data. This can become a complicated taskdepending on the target animal. For example, the life spanof the average broiler chicken is 6 to 7 weeks and theseanimals very often need to be vaccinated against a series ofpathogens (amongst others, Marek’s disease virus,Newcastle disease virus, infectious bronchitis virus,Gumboro disease virus) very early in life, i.e. before the ageof 14 days. Compatibility of the new product with all ofthese vaccines must be shown if this use is claimed. Thiswill involve safety studies as well as efficacy studies.Obviously, if it is claimed that a vaccine can be physicallymixed with another product and subsequentlyadministered, data from safety and efficacy studies must bepresented to support such a claim.

RecommendationsSpecific recommendations have to be provided that aid inthe most efficient use of the product. Suchrecommendations vary with the particular product.Obvious recommendations are to only vaccinate healthyanimals in the case of vaccines for prophylactic use. Apartfrom vaccines against cattle ringworm, no therapeuticvaccines are currently licensed, but they are envisaged forthe future (e.g. for the treatment of leishmaniosis). In thecase of live vaccines against pathogens that can becontrolled by chemotherapeutics, it may be important torecommend a withdrawal period after chemotherapeutictreatment before administering the live vaccine. Likewise,it may be sensible to advise minimisation of the risk ofconcurrent infections during the vaccination period, asthese could interfere with the induction of the properimmune response.


Post-marketing requirements

Following the granting of a marketing authorisation in theEU, each batch of vaccine that has satisfactorily undergoneall the finished product testing can be placed on the marketin all European member states. In some countries,however, a batch may only be placed on the market afterofficial release by the competent authority in the EUmember state concerned. For a few vaccines, e.g. rabiesvaccines, release onto the market is not authorised until anofficially appointed laboratory has re-tested the batch anddeclared that it is in compliance with the registeredspecification.

As with other regions of the world, pharmacovigilance isstrictly applied in the EU and has become the acceptablereplacement for the previous requirement to apply torenew a marketing authorisation every five years.

Requirements for theregistration of veterinaryvaccines in the United States of America

Who regulates veterinary vaccines?

The Center for Veterinary Biologics (CVB), under theumbrella of the USDA, is tasked with implementing theprovisions of the Virus-Serum-Toxin Act passed in 1913.The CVB is divided into two sections: Policy, Evaluation,and Licensing (CVB-PEL) and Inspection and Compliance(CVB-IC). The CVB regulates vaccines, bacterins andbacterial extracts, antibody products, diagnostic products,antitoxins, toxoids, and other products of biological origin.As stated in the section on EU requirements, this articlewill focus mainly on the requirements for viral andbacterial live and inactivated vaccines.

Basic registration requirements

Veterinary biologics manufactured in the USA must have aUS Veterinary Biologics Establishment License and a USVeterinary Biological Product License for each separateproduct. The requirements for labelling, for manufacturingprocesses, and for obtaining an establishment licence anda product licence, can all be found in Title 9 of the Code ofFederal Regulations. Additional guidance can be found inpublished memorandums and notices. Veterinary biologicsmust be proven to be pure, safe, potent, and effective priorto licensure and upon release of each serial. Applicants areencouraged to interact with CVB-PEL personnel asnecessary to facilitate submissions.

Contact with the CVB is via a person designated as theofficial (primary) liaison. The CVB sends all official mail tothe official liaison. Alternate liaisons can be designated toassist the liaison in signing certain documents such asofficial correspondence and APHIS Form 2015, which isused for submission of labels, circulars, and ‘Outlines ofProduction’.

Quality

ManufactureEach Veterinary Licensed Establishment in the USA mustsubmit and maintain the qualifications of supervisorypersonnel and facility documents, which includeblueprints, plot plans, and legends. The manufacturer isrequired to review and update these documents annually.

A manufacturer is required to submit and obtain CVBapproval of an Outline of Production detailing key steps inthe manufacturing process for each licensed product. Dataon three consecutive pre-licensing serials must bepresented to show that the manufacturer is able to producethe vaccine in a consistent manner. Consistency ofproduction is monitored by the agency through the use ofthe approved Outline of Production, release tests, andunannounced inspections.

Seed stocks of the vaccine strain are laid down in a seed lotsystem, making passages from the master seed to establishworking seed stocks from which all production batches areproduced.

As stated in the section on the European Union, the historyof the isolation and previous passages of the initial masterseed must be known in order to minimise the risk oftransmitting TSEs. Cell lines used in the productionprocess must also follow the seed lot system. Both masterseed stocks and master cell stocks must be approved by theCVB for use in production of a licensed product.

TestingPurityThe Outline of Production for all veterinary biologicalproducts must include a description of the procedures thatare to be followed in order to keep the product free fromany viable contaminating microbiological agents. In thespecific case of live vaccines, the product should notcontain microbiological agents other than the vaccinestrain(s). Consequently, it must be ensured that the masterseed stock from which all subsequent vaccine serials willbe derived is free from extraneous agents. Regulationsrequire that master seed and final container testing bedescribed in the Outline of Production. Final containers ofeach serial and subserial are tested as follows: for virusvaccines, demonstration of freedom from contaminatingbacteria, fungi, mycoplasma, and, in some cases, specificextraneous viruses; for bacterial vaccines, demonstration of


freedom from contaminating bacteria and fungi. The wordused to describe freedom from extraneous microorganismsor material is ‘purity.’

IdentityIn addition to purity, master seeds for all product types andfinal container samples of vaccines of each serial orsubserial must be tested to ensure it is identified as thecorrect strain. Subtypes and serotypes may also be tested ifthought necessary. Identity of final container samples maybe demonstrated in conjunction with potency testing byfluorescent antibody staining, serological methods,challenge of vaccinates, or other in vitro methods, such asELISA techniques.

Finished product testingTo ensure that each serial (batch) and subserial of acommercial vaccine is equivalent in quality and willtherefore be safe and efficacious, the manufacturer mustfile in the Outline of Production all relevant tests to beperformed on the finished product, giving limits ofacceptance that must be met before the serial or subserialcan be released. Only the CVB can release a product fordistribution and sale. In the US system, a manufacturersubmits a summary of all relevant tests on an official form(APHIS Form 2008) for each serial and subserial. Once aserial or subserial is produced and representative samplesare submitted, the serial or subserial may be randomlypicked for confirmatory testing. After the firm submitsAPHIS Form 2008 at the conclusion of their testing, if theserial or subserial is not chosen for confirmatory testing orif the confirmatory testing has been completedsatisfactorily, the product is released by the CVB fordistribution and sale. The type of tests performed mayinclude:

– sterility/purity tests for absence of contamination

– antigen quantification tests (e.g. ELISA and tests todetermine titre, cell count, optical density, etc.)

– tests for complete inactivation (inactivated vaccinesonly)

– physico-chemical tests, e.g. pH, viscosity of emulsion,quantity of residual inactivant, etc. (mainly valid forinactivated vaccines)

– tests to establish titre/potency (titre mainly for livevaccines) of finished product (see section on ‘Potency’below)

– safety tests in target or laboratory animals.

All tests are described in Title 9 of the Code of FederalRegulations and are based on use of the final product inpoultry or non-poultry, and on product type, i.e. live orinactivated (see the next section on ‘Safety’).

In addition, the manufacturer must prove that the qualityof the vaccine is guaranteed until the end of its shelf life.To demonstrate this, several serials of vaccine must betested at regular intervals throughout the proposed shelf life.

Safety

It must be shown, of course, that the product is safe for thetarget animal, but documentation must also be providedwhich demonstrates that the product is safe for theenvironment, for other animals, and for humans that maycome into contact with the product. Extensive literaturesearches into the background for each master seedcandidate are required prior to CVB approval of thatmaster seed. The manufacture may be required, for certainproducts, to conduct risk analysis to assess the potentialeffects of the product on the safety of animals, publichealth and the environment. An environmental assessmentwill be prepared to address the requirements of theNational Environmental Policy Act of 1969. Themanufacturer, in agreement with the CVB, may conductadditional tests if needed to provide additional proof of thesafety of the strain used.

Prior to licensure, a target animal field safety studyfollowing product label directions must be conducted. Thestudies are generally performed on at least two serials andin at least three geographical locations. Animal numbersshould take into account label recommendations such asage, site of administration, sex, breed, pregnancy,protection claims in neonates, and any otherdistinguishing features. If the vaccine is intended foradministration to pregnant animals, additional data may berequired.

A live vaccine strain must be stable, i.e. should not revertto virulence during consecutive passages. Depending onthe agent, recombination or genomic reassortment needsto be evaluated. Vaccines are produced within a specifiednumber of passages from the master seed stock. Usuallythis is limited to five passages for virus vaccines and higherfor bacterial vaccines. The safety of the vaccine strain at thelowest passage number is shown in animal studies usingthe most sensitive target animal/species. Aspects such asspread of the vaccine strain and dissemination in thevaccinated animal need to be taken into account whereappropriate. Also, studies on the immunological functionsmay have to be carried out where the vaccine mightadversely affect the immune response.

Efficacy

Data must be provided that support the efficacy claims.There are four predefined claims supported by the CVB:prevention of infection, prevention of disease, aid indisease prevention, and aid in disease control.


Manufacturers are encouraged to interact with CVB whenplanning the protocol for these studies, which are requiredto be laboratory controlled studies, not field performancestudies. Experimental product used in the studies must beprepared from the highest passage from the master seedstock, and if cell culture is used in manufacturing it mustbe prepared at the highest passage from the master cellstock allowed in the Outline of Production. The studiesmust be conducted at or below the minimum antigen levelneeded for efficacy, which is also specified in the Outline ofProduction.

Potency

As in the EU, the manufacturer must provide data thatguarantees the immunising capability and therebyprotective effect of a product. In vivo or in vitro testing canbe used for this purpose. Both the CVB and manufacturersare moving away from animal testing toward in vitro tests.

For release of finished product, a pre-calculated titre valueis added to the minimum antigen level demonstrated forefficacy. For live virus vaccines, the titre required throughdating must be at least 0.7 log10 greater than the titre usedin the efficacy study. For live bacterial vaccines, thebacterial counts required through dating must be twicethose used in the efficacy study. Expected loss in stabilityor via steps in production should be added to these values,normally 0.5 log10 to the live viral products.


Registration of the label claimIn the USA, the licence is granted with a CVB approvedOutline of Production, label, and circular. The CVB assignsa ‘true name’ and a product code number that is used todifferentiate the biological product from others. This truename must be listed prominently on all packagingcomponents. The Outline of Production includes thehistory and test methods used to support the master seedstocks. The Outline includes the passage details, source ofmedia used, in-house testing as well as serial releasetesting, expiration dating confirmation, efficacyconfirmation, release titres, and description of finalproduct containers, use of the product, and storageconditions. Changes to the Outline of Production must bepre-approved by the CVB.

Target animalAs with the EU regulations, clearly, it must be specified forwhich animal species the product is intended. In addition,the category must be stated, e.g. whether the product canbe used safely in pregnant animals or is intended forspecific use, such as for broiler chickens as opposed tobreeder chickens or layer flocks. The CVB also grants anautogenous licence for inactivated viral or bacterialproducts. This type of product has a very special use in theflock or herd of origin.

Route of administrationJust as in the EU, studies must be performed to support thesafety and efficacy claims of each route of administration(e.g. oral application, injection) and the claims must beclearly stated in the Outline of Production and on the labeland circular.

Onset and duration of immunitySpecial efficacy trials are designed around claims for onsetand duration of immunity. Trials to test duration ofimmunity claims take the form of efficacy studies in whichthe animals are vaccinated according to the directions foruse, and then challenged at a specified time, i.e. one yearor three years post vaccination. Data from non-challengestudies (publications, studies not used to supportlicensure, etc.) must be pre-approved through the CVBbefore a manufacturer is allowed to make such claims.

CompatibilityFor those vaccines used in combination, additionalsupporting data must be submitted. Combination productshave two or more antigens in one vial or are prepared bymixing two or more separately licensed products in thefield. Of course, the efficacy of each fraction must beproven, but a lack of interference must also be establishedbetween fractions. Challenge or serology models may beused. These studies may be used to recalculate theminimum potency level at which the product will bereleased.

Requirements for theregistration of veterinaryvaccines in Japan

Quality

Manufacture

Both the antigen and the vaccine must be manufacturedaccording to GMP. A manufacturing licence must beobtained for each production facility where the antigen orvaccine is being produced or stocked for sale. An overseasproduction facility which intends to export vaccines toJapan must be accredited by MAFF in Japan in advance.This accreditation is renewed every five years. A marketingauthorisation must be obtained by a marketing licenceholder prior to sale of the vaccine in Japan.

As a precaution against the risk of contamination withbovine spongiform encephalopathy strict regulation isapplied to the use of any raw materials of ruminant originfor production of veterinary vaccines regardless of theintended target animal species. For example, milk and


dairy products from the United Kingdom and Portugalcannot be used, and bovine serum and bovine serumproducts from the USA have to be certified as notoriginating from a TSE-affected bovine herd in the USA.

National assay

In Japan, each batch of a veterinary vaccine is tested by theNational Veterinary Assay Laboratory (NVAL) forconformance to the respective monographs published inthe Standards of Veterinary Vaccines for National Assayprior to release of the batch on the market. This ‘nationalassay’ process requires the sponsor of a veterinary vaccineapplication to propose those testing methods which areeasily practicable by the NVAL in the registration dossier.The Standards also stipulate general test methods that areused in the national assay.

While some of these test methods have been globallyharmonised thanks to the VICH initiative, some other testmethods remain unique to Japan and the sponsor oftencarries out the test according to the method used in Europeor the USA and then repeats the same test according to theJapanese method (sterility test for example) whenexporting a vaccine to Japan from the USA or Europe.

MAFF is currently planning to introduce a full seed lotsystem in the near future and the national assay processwill be simplified or eliminated depending on the type ofvaccine to be tested.

Potency test

In Japan, traditionally an in vivo potency test has beenrequired as part of the batch release control procedure ofpractically all veterinary vaccines, including live vaccines.This is usually performed by a serological technique suchas neutralisation, haemagglutination inhibition or ELISA,but sometimes a challenge test is also performed. Thepotency test has to be correlated with the efficacy of thevaccine. Since this is not a requirement for a live vaccine inthe USA or Europe, a sponsor usually has to develop avalidated in vivo potency test for registration of a livevaccine in Japan.

Abnormal toxicity test

The abnormal toxicity test in mice and guinea pigs, or atoxicity limit test in either of these species, which is amodified version of the abnormal toxicity test, is requiredas part of the batch release control of all mammalianvaccines. The abnormal toxicity test is not routinelyconducted in the USA or Europe.

Safety test

Safety testing in the target animal species is required in thebatch release control of all veterinary vaccines except for

large animal vaccines (swine, cattle and horses). In the caseof poultry vaccines, reporting of non-specific mortality inthe safety tests is not accepted unless the cause of death isshown to be irrelevant to the vaccine, whereas a certainnumber of non-specific deaths are accepted in the safetytest in chickens in the USA and Europe.

Physico-chemical and biological properties

Physico-chemical properties such as morphology of thevaccine strain and biological properties such as virulenceof the vaccine strain in various cell lines or laboratoryanimal species, and comparison with a standard referencestrain should be included in the registration dossier. Inaddition, data on immunogenicity, growth characteristicsand, where applicable, interference between antigensshould be submitted. For a live vaccine, data onidentification of the marker of attenuation and the strain aswell as the marker stability, shed and spread, and reversionto virulence should be submitted. An outline of productionis also required. Three pilot batches should bemanufactured and tested according to the proposedspecification and test methods.

Stability

In the stability test, three pilot batches are stored under theproposed storage conditions for the proposed shelf lifeperiod. Each individual vaccine sample should be withinthe proposed specification at all time points throughoutthe storage time, whereas a statistical approach is oftenused in the interpretation of the stability test in the USAand Europe. Stability after reconstitution of the vaccine,where applicable, and changes at room temperature shouldalso be investigated.

Safety

In Japan, a target animal safety study requires that a groupbe given a recommended dose and another group be givenan overdose equivalent to 100 times the recommendeddose for live vaccines or 10 times the recommended dosefor inactivated vaccines, administered in divided doses toavoid causing physical harm to the test animals. The studyshould normally use the final vaccine, i.e. the vaccine thatis to be registered. Use of target animal safety data obtainedwith a maximum combination vaccine for the registrationof a combination vaccine containing fewer antigens isgenerally not accepted, unlike in the USA or Europe. For avaccine for food-producing animals containing adjuvant,depletion of adjuvant must be investigated in addition tonormal histopathology. An appropriate withdrawal periodis established based on depletion of the adjuvant andresolution of the lesions at the injection site. All the targetanimal safety studies must be conducted in accordancewith the GLP guidelines.


Efficacy

Efficacy studies consist of basic studies supporting efficacyand field trials. Basic studies supporting efficacy shouldnormally include:

– establishment of minimum effective antigen dose

– establishment of minimum protective antibody titreagainst the target disease

– determination of duration of immunity

– establishment of the relationship between the antigendose and the antibody titre

– analysis of the relationship between local immunity andthe protection induced

– comparison of response between different ages, breedsand routes of administration

– analysis of protective mechanism

– determination of the relationship between thematernally derived antibody and the protection induced.

In addition, data must be presented on onset of immunity,the effect of booster vaccination and the effect of othervaccines that are likely to be administered concurrently.Field trials, usually at two or more locations in Japan, arerequired to provide safety and efficacy data from aminimum of 60 animals for a mammalian vaccine or 200birds for a poultry vaccine. Usually, all animals, or justcertain individual animals, have to be monitoredperiodically for serological responses to each antigencontained in the vaccine. Field trial data collected inforeign countries are accepted if the epidemiology and thetrial protocol are similar, but even in this case, at least onelocal field trial is required. Field trials must be conductedin accordance with the GCP guidelines.


Generic vaccine

In the case of a vaccine that is considered equivalent tothose vaccines that are already registered in Japan (e.g. avaccine containing a different strain but having similarbiological properties, similar composition, similar dosageand administration instructions and the same indication) asample of the vaccine has to be submitted to the NVAL forconfirmation of equivalence. Once such confirmation isobtained from the NVAL, the registration processsubsequently becomes much simpler compared with thatof a new vaccine.

Food animal vaccine

The dossier on a new food animal vaccine is reviewed notonly by MAFF but also by the Food Safety Commission

(FSC), which reports to the Prime Minister’s Office on thepossible impact on human health. The review by the FSCconsists of several steps, including an invitation for publiccomment, and it usually lengthens the regulatory approvalprocess by 6 to 12 months.

Recombinant vaccine

Detailed requirements for registration of a recombinantvaccine in Japan remain somewhat vague and theguidelines for application of the Cartagena Protocol toveterinary vaccines are still awaited. To date, norecombinant vaccine has been approved in Japan.

Requirements for theregistration of veterinaryvaccines in AustraliaAustralia is considered an advanced country from the pointof view of registration of vaccines. Vaccine products areregistered and their accompanying labels are approved bythe government regulator prior to marketing. The basis ofapproval of vaccines is essentially similar to that in the EUor USA, but the process of registering differs in somerespects.

Pre-marketing requirements

Australia maintains a national registration scheme forveterinary products which is administered by the federalgovernment on behalf of the Australian States andTerritories. All vaccines must be registered by theAustralian Pesticides and Veterinary Medicines Authority(APVMA) in accordance with the Agricultural andVeterinary Chemicals Act 1994 and the Agricultural andVeterinary Chemicals Code Act 1994 and other supportinglegislation. Once APVMA registration is granted, state bystate registration is not required.

All registered vaccines must be manufactured in a facilityapproved by the APVMA under the Manufacturer’sLicensing Scheme. Mutual Recognition Agreements existbetween the APVMA and some other countries and othersare recognised under the Overseas GMP Scheme.

Although the APVMA has its own format for thepresentation of data for the registration of vaccines, thecontent is essentially the same as that for other advancedcountries (it is particularly similar to the data required inthe EU). Data presented in the format of another countryis generally acceptable so long as effective cross-referencingis provided in an Australian format dossier. The APVMAdoes not accept phased filing in the same way as the USDA.Australia has so far adopted all VICH guidelines without


any modification in the case of vaccines. It is a defaultrequirement that local efficacy data is presented forvaccines, but this is negotiable with the APVMA on thebasis of scientific argument; this requirement is morestrongly enforced for economic animals than forcompanion animals.

A summary of each application for registration is publishedon the APVMA website at the start of the review processtogether with, for some applications, a list of supportingtrial data for the purposes of establishing data protection.All new active ingredients (including new antigens) aresubject to public comment before registration is finalised.At the time of registration, a summary is published ofadvice on the application received from other authoritiesor external assessors.

Imported vaccines or locally produced vaccines containinganimal-origin materials of overseas origin require priorclearance by the Australian Quarantine and InspectionService (AQIS) (see the section on ‘Biosecurity’ below).

Vaccines derived from biotechnology require priorclearance or exemption by the Office of the GeneTechnology Regulator.

The APVMA publishes guidelines for the time frame forregistration review to which it aims to adhere. The final actin the registration process is the submission and approvalof the final product label, which must conform to localguidelines.

Post-marketing requirements

Finished-product testing and release is carried out by thelicensed manufacturer. The maintenance of appropriaterecords is a requirement of GMP compliance and is subjectto periodic inspection. There is no requirement for batchrelease by the regulatory authority (but see ‘Biosecurity’below).

All registrants are required to maintain apharmacovigilance programme and lodge annual or, insome cases, real-time reports.

An annual renewal fee for each registered vaccine ispayable to the APVMA, together with a levy on sales.Periodic re-submission of data is not a requirement unlessrequested by the APVMA under its Existing ChemicalReview Program.

Biosecurity

Australia enjoys a fortunate freedom from a number ofinfectious animal diseases and guards this status jealously.Its strict quarantine regulations and policies are establishedby Biosecurity Australia and policed by AQIS. An in vivopermit must be obtained from AQIS for each vaccine, oranimal-derived raw material intended for use in a vaccine,imported to Australia. All imports are checked at theborder for correct documentation. Application for such apermit requires submission of a substantial body ofbiosecurity data and a potentially prolonged review period(no published time frame). Permits issued for the import ofvaccines are generally for a finite period and usuallyrequire a compliance audit to be conducted by AQIS oneach serial imported. The stringency of these requirementsshould not be under-estimated.

AcknowledgementsThe authors would like to thank Dr Kent MacClure,Animal Health Institute, Washington DC, who kindlyundertook the proof-reading of the text of this paper.



Exigences réglementaires liées à l’agrément des vaccins

P.G.H. Jones, G. Cowan, M. Gravendyck, T. Nagata, S. Robinson & M. Waits

Résumé

Les vaccins sont l’un des principaux outils pour prévenir et maîtriser les

maladies animales. Dès lors, il est d’une importance capitale que les vaccins

soient utilisés conformément aux prescriptions du Code sanitaire pour les

animaux terrestres (Code terrestre) de l’Organisation mondiale de la santé

animale (OIE) après avoir été avalisés par l’organisme chargé de délivrer les

autorisations de mise sur le marché dans le pays/la région où les vaccins doivent

être utilisés, en respectant les critères fondamentaux de qualité, de sécurité et

d’efficacité.

Les auteurs examinent et comparent les exigences réglementaires en vigueur

pour les vaccins vétérinaires dans les principales régions du monde, en

soulignant les similitudes ainsi que les différences constatées. Ils décrivent

également les derniers progrès accomplis dans le domaine de l’harmonisation

des exigences relatives aux tests, grâce à la Coopération internationale sur

l’harmonisation des exigences techniques applicables à l’enregistrement des

médicaments vétérinaires (VICH). Cet article fournit des orientations utiles pour

tous ceux qui s’occupent de recherche et de développement de vaccins dans le

monde, tout en apportant aux personnes chargées de la prévention et de la lutte

contre les maladies animales la garantie que les vaccins vétérinaires, dès lors

qu’ils sont dûment autorisés et utilisés suivant le mode d’emploi prescrit, sont

sûrs et efficaces.

Mots-clés

Coopération internationale sur l’harmonisation des exigences techniques applicables à

l’enregistrement des médicaments vétérinaires (VICH) – Dispositions réglementaires –

Efficacité – Harmonisation – Qualité – Sécurité – Vaccin vétérinaire.


Requisitos de las reglamentaciones relativas

a la autorización de comercialización de vacunas

P.G.H. Jones, G. Cowan, M. Gravendyck, T. Nagata, S. Robinson & M. Waits

Resumen

La vacunación es uno de los instrumentos existentes más eficaces para prevenir

y controlar las enfermedades animales. Por consiguiente, es indispensable que

su administración se conforme a las disposiciones del Código Sanitario para los

Animales Terrestres (denominado también “Código Terrestre”) de la

Organización Mundial de Sanidad Animal (OIE) y haya sido autorizada por el

organismo habilitado para la concesión de licencias de comercialización del

país o región interesados, de conformidad con los criterios clave relativos a la

calidad, inocuidad y eficacia.

Los autores exponen las exigencias sobre las vacunas veterinarias de las

reglamentaciones en vigor en las principales regiones del mundo de manera

pormenorizada y comparada, destacando sus similitudes y diferencias. También

reseñan los últimos avances realizados por la Cooperación Internacional para la

Armonización de los Requisitos Técnicos relativos al Registro de Medicamentos

de Uso Veterinario (VICH) en la armonización de los requisitos que han de

atenderse durante las pruebas. Este artículo, que constituye una valiosa guía

para quienes trabajan en la investigación y el desarrollo de vacunas en todas

partes del mundo, demostrará a quienes participan en la prevención y el control

de las enfermedades animales que las vacunas de uso veterinario, una vez

aprobadas y administradas conforme a las instrucciones del fabricante, son

inocuas y eficaces.

Palabras clave

Armonización – Calidad – Cooperación Internacional para la Armonización de los

Requisitos Técnicos relativos al Registro de Medicamentos de Uso Veterinario (VICH) –

Eficacia – Inocuidad – Requisito reglamentario – Vacuna veterinaria.


Regulatory issues surrounding the temporary

authorisation of animal vaccination in emergency

situations: the example of bluetongue in Europe

C. Saegerman (1), M. Hubaux (2), B. Urbain (3), L. Lengelé (2) & D. Berkvens (4)

(1) Department of Infectious and Parasitic Diseases, Epidemiology and Risk Analysis Applied to Veterinary

Sciences, Faculty of Veterinary Medicine, University of Liège, Boulevard de Colonster, 20, B42, B-4000 Liège,

Belgium

(2) Directorate-General for Animals, Plants and Foodstuffs, Federal Public Service of Public Health, Food

Chain Safety and Environment, Eurostation II – 7th floor, Place Victor Horta 40 box 10, B-1060 Brussels,

Belgium

(3) Marketing Authorisation Veterinary Unit, Federal Agency for Medicinal and Health Products, Eurostation II

– 8th floor, Place Victor Horta 40 box 40, B-1060 Brussels, Belgium

(4) Department of Animal Health, Unit of Epidemiology and Applied Statistics, Prince Leopold Institute of

Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium

Summary

A marketing authorisation for a veterinary vaccine is granted after the quality,

safety and efficacy of the product have been assessed in accordance with legal

standards. The assessment includes complete characterisation and

identification of seed material and ingredients, laboratory and host animal safety

and efficacy studies, stability studies, and post-licensing monitoring of field

performance. This assessment may not be possible during the emergence of a

new animal disease, but several mechanisms exist to allow for the availability of

products in an emergency animal health situation, e.g. autogenous biologics,

conditional licences, experimental and emergency use authorisations, the

importation of products in use elsewhere in the world and pre-approved vaccine

banks. Using the emergence of bluetongue in northern Europe as an example,

the regulatory issues regarding the temporary authorisation of animal

vaccination are described. Several conditions must be fulfilled before a

temporary authorisation can be granted, e.g. inactivated vaccines should be

used in order to exclude reversion to virulence and reassortment between

vaccine viruses and/or field strains of the bluetongue virus; decision-making

must be supported by scientific evidence and risk analysis; there must be a

complete census of the susceptible animals that were vaccinated; vaccination

protocols must be adhered to and there must be a scheme allowing for

registration, delivery and follow-up of vaccination, and monitoring, analysis and,

possibly, adjustment of field use of the vaccination. This temporary authorisation

must be replaced by a full authorisation as quickly as possible.

Keywords

Animal health – Emerging disease – Regulatory issues – Temporary authorisation –

Vaccination – Vaccine.

IntroductionEach and every animal disease control and/or eradicationprogramme is based on two general principles:

a) the control of infected herds through the application ofcorrective control measures

b) the protection of infection-free herds throughpreventive measures.

The identification of individual animals and herd registersare two essential prerequisites before these principles canbe applied. The herd is the epidemiological unit of interestin disease control programmes.

The above indicates that different strategic options can beadopted, separately or conjointly, firstly to decrease theprevalence to an acceptable level (disease control) andsecondly to eliminate the remaining clinical or sub-clinicalinfection foci (disease eradication). The overall strategyconsists of one or more of the following steps:

a) generalised compulsory vaccination of the entiresusceptible population (medical prophylaxis);

b) slaughter of known infected animals (test and slaughter)combined with a selective vaccination programme,including either only the subclass of animals at risk (e.g.young naive animals) or all animals in a limited areadepending on the prevalence (medico-sanitary prophylaxis)

c) stamping out of animals known to be infected orexposed (sanitary prophylaxis). Adequate compensation forthe animals slaughtered is an unavoidable requirement forsuccess of the programme (86).

The choice of the different steps to be undertaken dependson a certain number of considerations, amongst them:

– infection prevalence in the different susceptible animalspecies (and human clinical incidence in the case of azoonosis)

– the structure and management of the livestock sector

– the availability of a national reference laboratory andregional laboratories

– the capacity of the Veterinary Services to follow up theprogramme and to control livestock movements and thecooperation between the Veterinary Services and theprivate sector in the implementation of such a programme

– the involvement of political decision-makers and theirwillingness to support an uninterrupted effort over manyyears, sometimes several decades

– the availability of financial resources and the capacity tomobilise extra funds

– the coordination and collaboration between the Healthand Agriculture Ministries when planning the programme

– the level of involvement of farmers organisations, whichideally should be convinced of the benefits of the exercisebefore the start of the programme (5, 86).

Each party concerned must participate in developing andimplementing disease control programmes, in financingthese programmes and in taking responsibility for theirimplementation, and each party must be rewarded for theirachievements. This is the principle of joint decision-making, joint financing and joint accountability (44).

A prerequisite for any programme is the implementation ofan efficient animal disease surveillance network, capable ofmonitoring the progress made, and being able to adjust thestrategy when required (55). Every programme musttherefore be evaluated regularly and performanceindicators must be set beforehand (87). Moreover, thestrategy must be adjusted not only according to theepidemiological situation, but also in the light of newscientific knowledge (86).

In the case of countries that are free of a disease vaccinationis usually not practised, but the option to use vaccinationin an emerging disease situation is still available (101).Moreover, policies involving mass slaughtering being lessand less popular, there is a tendency to use so-calledmarker vaccines together with a companion diagnostic test(33, 76).

A marketing authorisation for a veterinary vaccine isgranted after the quality, safety and efficacy of the producthave been assessed in accordance with legal standards (18,22, 48). Even when using an accelerated assessmentprocedure it can still take a long time before authorisationis granted. However, Member States are authorised to usevaccines without a marketing authorisation in anemergency situation. Using the example of the emergenceof bluetongue (BT) in Europe, the advantages anddisadvantages of this temporary authorisation permit arediscussed and solutions to improve this unusual situationare proposed.

Emergency situationsSeveral definitions of an emerging disease coexist (9, 13,69, 77) but they all have a common denominator. Anemerging disease is a disease of which the true incidenceincreases in a significant way in a given population, in agiven area and during a given period, in comparison withthe usual epidemiological situation of this disease (103).This increase in true incidence is due to several factors,such as the evolution or the modification of a pathogenicagent or an existing parasite, which results in a change ofhost, of vector, of pathogenicity or strain (68, 116).Specific social, ecological, climatic, environmental and


demographic factors precipitate the emergence of a disease(69, 97, 113, 114), but it is difficult to establish a rankingof causes or of mechanisms (81).

There are several models for understanding emerging risks,they include:

a) the convergence model for zoonotic diseases (53)

b) the pan European pro-active identification of emergingrisks in the field of food production model (PERIAPT)concerning emerging risk in the food chain (108)

c) the generalised model for rare events (85, 87).

The example of the recent BT epidemic in northern Europeis treated more in detail hereafter (24, 43, 102, 104).

Bluetongue virus (BTV) is the prototype species of thegenus Orbivirus in the family Reoviridae. The viral genomeconsists of 10 double-stranded RNA segments that encodefor four non-structural (NS1, NS2, NS3 and NS3A) andseven structural (VP1-VP7) proteins (82, 111). Currently,there are 24 known serotypes of BTV worldwide (63).However, a genetic diversity of BTV exists and it is aconsequence of both drift (i.e. point mutations) and shift(i.e. reassortment of individual BTV gene segments).Serotypes 1, 2, 3, 4, 6 and 10 are known to have a highpathogenic index and high epidemic potential (18).Bluetongue is a notifiable disease of the WorldOrganisation for Animal Health (OIE), and is thus ofserious socio-economic concern and of major importancein the international trade of animals and animal products(18). The BTV is transmitted between its ruminant hostsexclusively by bites of Culicoides midges (60, 61).Transmission is limited to seasons during which adultinsects are active. Bluetongue is thought to infect allknown ruminant species. However, severe disease usuallyoccurs only in certain breeds of sheep and in some speciesof deer (57, 74, 100). Both cattle and goats suffer fromunapparent infection, but probably serve as importantreservoirs of the virus for sheep and wild ruminants (57,109). Common clinical signs include fever, salivation,abundant nasal discharge, oedema (particularly in the headregion), congestion, ulcerations of the oral mucosa,lameness, depression and, sometimes, cyanosis of thetongue (45, 57). The mortality rate and the severity of theclinical signs seem to be dependant on factors such as thebreed and age of the animal infected (older age groupsbeing more susceptible) and the type and strain of the virus(62). Because BTV infection is not contagious, meat anddairy products pose no hazard for the spread of thepathogen in ruminants. However, blood and otherbiologicals for cell culture or in vivo use are a potential riskfor spread (20, 118).

The genus Culicoides comprises 1,260 species, of which 30,to a greater or lesser extent, are involved in the

transmission of orbiviral diseases injurious to livestockalmost worldwide. Until recently, Culicoides imicola(Kieffer) was believed to be the only vector of BTV in bothAfrica and southern Europe (43), but it is now known thatother newly identified (and as yet unidentified) vectors areinvolved. Other possible factors that have contributed tothe spread of BTV include animal migration andimportation, extension in the distribution of its majorvector, Culicoides spp., the apparent ability of the virus tooverwinter in the absence of adult vectors, and itsoccurrence in healthy reservoir hosts, such as cattle andsome wild ruminants (18, 79, 99).

In 2004, bluetongue was reported in nine countries in theworld (115) (Fig. 1). Between 1998 and 2004, when therewere incursions of BTV into the Mediterranean Basin, theBalkans and beyond (Table I), the disease penetrated intoareas where C. imicola does not occur, thus incriminatingnovel vectors (3, 8, 12, 42, 62, 64, 119). This wasconfirmed subsequently when the causative virus wasisolated from mixed pools of the two species Culicoidesobsoletus (Meigen) and Culicoides scoticus (Downes andKettle) collected in central Italy (92, 93) and fromCulicoides pulicaris (Linnaeus) in Sicily (11).

Bluetongue appeared for the first time in the north ofEurope (Fig. 2) following a heat wave and strong rains, andcan be defined as being an emergent disease in this zone(116). After the first notification on 17 August 2006 (19),more than 1,200 cases of BT were entered in the EuropeanCommission’s Animal Disease Notification System(http://ec.europa.eu/food/animal/diseases/adns/index_en.htm). In this area, BTV was isolated from Culicoides dewulfi(Goetghebuer) (58), an indigenous European Culicoidesspecies (Fig. 3) – thereby increasing the risk oftransmission over larger geographical regions (42, 79).


Fig. 1

Bluetongue throughout the world in 2004

Source: Handistatus II (http://www.oie.int/hs2/report.asp?lang=en)

(115)


Table I

Outbreaks of bluetongue in Europe in the period 1998-2004

(7, 62, 75, 115)

Country Year of first outbreak Serotype(s) of bluetongue virus Main vector(s) identified

Albania 2002 9 Culicoides obsoletus, C. pulicaris

Bosnia-Herzegovina 2002 9 ND

Bulgaria 1999 9 C. obsoletus, C. pulicaris

Croatia 2001 9, 16 C. obsoletus, C. scoticus

Cyprus 2003 16 C. obsoletus, C. pulicaris

Former Yugoslav Republic of Macedonia 2001 9 ND

France (Corsica) 2000 2 C. imicola, C. pulicaris, C. obsoletus

Greece 1998 1, 4, 9, 16 C. imicola, C. obsoletus

Italy 2, 9, 16 C. imicola, C. obsoletus, C. pulicaris

Kosovo 2001 9 ND

Portugal 2004 ND (a) C. imicola, C. obsoletus, C. pulicaris

Serbia and Montenegro 2001 9 ND

Spain 2000 2 C. imicola, C. obsoletus, C. pulicaris

Turkey 1999 9, 16 C. imicola

ND: no data recorded

a) Probably serotype 4

Black circle (Belgium; n = 460)

Red circle (Germany; n = 457)

Yellow circle (Netherlands; n = 306)

Blue circle (France; n = 5)

Fig. 2

Bluetongue outbreaks (serotype 8) in northern Europe between 17 August and 25 October 2006

Source: European Commission’s Animal Disease Notification System, 2006

This recent finding is an important new epidemiologicalevent, because previously most BT outbreaks were linkedto C. imicola. Culicoides dewulfi has been reportedthroughout the Palaearctic area (52, 105). This indicatesthat the disease could now remain in the rest of Europewhere cattle and horses are kept (C. dewulfi is known tobreed in cattle dung and horse dung), with the risk of morecases of orbiviral diseases such as BT occurring during thefollowing spring when the vector activity is high (58).

The global distribution of the BTV endemic areas hastraditionally been accepted to be between the latitudes ofapproximately 50°N and 35°S (17, 54, 61, 80). There isnow enough scientific evidence to show that it has spreadfurther north, to 53°N (58, 117).

Vaccination as a strategic optionStrategies for controlling BT range from control measuresin areas free from the disease to systematic vaccination inBT endemic areas. In areas free from BT but whereCulicoides spp. are present, any introduction of live animalsfrom infected countries should be controlled bearing inmind the maximum duration of viraemia (e.g. quarantinefor at least 60 days is recommended by the OIE). Whenimporting ruminant semen or embryos/ova from suspectedinfected areas, donors are kept in quarantine and protectedfrom potential vectors for at least 60 days prior tocollection, or donors are tested according to the protocoloutlined in the OIE Terrestrial Animal Health Code (118). Inrecently infected areas, eradication of BTV is theoreticallypossible by adopting a range of methods, including someor all of the following:

– animal movement restrictions

– serological/virological surveys and slaughtering ofinfected and potentially infected animals

– vaccination and/or vector control (e.g. use of insecticideor keeping animals indoor during periods of high vectoractivity) (Table II).

In areas where BTV is enzootic, controlling the vectors isusually considered to be impossible and any reduction intheir numbers is transient (56). Nevertheless, attempts tocontrol vector populations have been implemented usingchemical repellents and/or insecticide treatment (6, 91, 98,112).

With regard to prophylaxis, possibly the best way tocontrol clinical BT outbreaks in endemic areas is to


Fig. 3

Gravid female of Culicoides dewulfi isolated near outbreaks

in Belgium in 2006

(Reginald De Deken and Maxime Madder, Institute of Tropical

Medicine, Antwerpen, Belgium)

Table II

Control, safeguard and preventive measures against bluetongue applied in Eastern Europe, 1998-2004

(adapted from 62, 75)

Control measures Safeguard measures Preventive measures

Modified stamping out policy, i.e. killing and destroying clinically Protection zone Vaccination

affected animals (viraemic animals) to prevent them acting as a Surveillance zone

source of virus for vector insects Restricting the movement of animals and germinal

Vector control measures by means of insecticides and/or insect products to prevent new foci or infection

repellents

Intensive clinical surveillance

Serological surveillance

Virological surveillance

Entomological surveillance


Table III

Available bluetongue vaccines

(according to 15, 18, 34, 94, 119)

Type (form) Species Valences Strains Producer

Inactivated (suspension) Sheep (a) Monovalent 2 & 4 Mérial SAS, Lyons, France

Polyvalent 16 & 9 in development

Sheep (b) Monovalent 2 Istituto Zooprofilattico Sperimentale

dell’Abruzzo e del Molise, G. Caporale,

Teramo, Italy

Attenuated (freeze-dried) Sheep (c) Monovalent Series of three separate injections Onderstepoort Biological Products,

with different serotypes Onderstepoort, South Africa

in each bottle (d)

Polyvalent (Can be produced on request (e))

Sheep Monovalent 4 Central Veterinary Control & Research

Institute, Ankara, Turkey

Sheep Monovalent 4 Biopharma, Rabat, Morocco

Sheep and goats Monovalent 10 Colorado Serum Co., Denver, Colorado,

Unites States of America

a) Indications for efficacy in cattle (94)

b) Immunogenicity was assessed by subcutaneously inoculating sheep, goats and bovines but only vaccinated sheep were challenged (15)

c) Indications for efficacy in cattle (65)

d) The vaccine is presented as: A (1, 4, 6, 12 & 14 serotypes); B (3, 8, 9, 10 &11 serotypes) and C (2, 5, 7, 13, & 19 serotypes)

e) Production of these vaccines requires two months for production and quality control (45)

Table IV

Advantages and disadvantages of a bluetongue vaccination strategy using attenuated vaccines

Advantages Reference Disadvantages Reference

Provision of an alternative to slaughter policies, which are 76 Risk of disease 110

becoming less and less popular Risk of reversion to virulence 18

Reduction of the intensity and duration of viraemia following 39, 41 Risk of reassortment of genome segments between 90, 95, 96

contact between vaccinated animals and wild-type strains vaccine and field viruses

of the bluetongue virus (progressive reduction of BTV Risk of foetal abnormalities (a) 32

transmission) Risk of introducing exotic serotypes into an ecosystem 59

Decrease in direct losses (number of outbreaks and 39, 41, 45 if using polyvalent vaccines (b)

diseased animals, mortality) Risk of inappropriate coverage in susceptible species 39

Decrease in indirect losses (exportation of live animals) 39 (at least 80% of the population) (c)

Risk of inappropriate coverage of all susceptible domestic 40, 59

ruminant species (not only sheep)

Costs of the implementation and monitoring of the 119

vaccination programme (serological, virological and

entomological surveillance)

a) This disadvantage is easily resolved because the manufacturer does not recommend this vaccine for use in pregnant animals (18)b) The most commonly used vaccines are those produced by Onderstepoort Biological Products Ltd, South Africa. A monovalent bluetongue vaccine is only produced on special request and its

production and quality control take two months (45)

c) This disadvantage is easily resolved by proper implementation and monitoring of the vaccination programme

BTV: bluetongue virus

vaccinate susceptible animals and limit contact betweensusceptible hosts and insect vectors (18).

Live attenuated vaccines have been available for manyyears (18, 94, 110). Inactivated vaccines have beendeveloped, but currently are less used (16) andrecombinant vaccines (83) are still under development(56) (Table III).

Attenuated vaccines

In South Africa, around eight million doses of attenuatedvaccines are used annually (18, 20). These vaccines arecheap, easy to produce and effective in controlling clinicaloutbreaks of BT in areas of endemic disease (18, 20). Theyreplicate in sheep without causing significant clinicaleffects and provide protection (humoral and cellularresponses) against challenge with virulent virus of the sameserotype (70). The vaccines most commonly used are thoseproduced by Onderstepoort Biological Products Ltd, SouthAfrica (45). Sheep are vaccinated three times every year atthree-week intervals with vaccines containing fiveserotypes each. As one of the side effects of these vaccinesis abortion, the last vaccination round has to be carried outthree weeks before the mating period (18). Very few soliddata have been published on the safety and efficacy of thesevaccines (18, 45, 50, 65, 66, 67). Potential safety issuesassociated with attenuated vaccines, although probably notlikely to occur often (no quantitative studies), are thefollowing:

– risk of foetal abnormalities

– risk of reassortment

– risk of reversion to virulence

– risk of transmission of vaccine strains by vector midges(Table IV).

Some attenuated BT vaccine strains were shown to beteratogenic in sheep when administered during the firsthalf of pregnancy (32). Attenuated BTV vaccine strainsmay be responsible for spontaneous cases of BTV-inducedmalformation in both sheep and cattle, but it is noted thatdifferent serotypes of BTV differ in their pathogenesis,transmissibility and growth characteristics (18). This riskmust be avoided by clear indication on the product labelthat pregnant ewes must not be vaccinated in the first halfof pregnancy.

The reassortment of genome segments between vaccineand field viruses has been demonstrated in the laboratory,but only rarely has it been reported to occur in the field(14, 46, 71, 89, 90, 95, 96). The reassortment ofteninvolves segments of different serotypes of the vaccine(110). The effect of such reasortmens in dually infectedvectors and/or hosts could result in altered viruscharacteristics and virulence (110). However, the risk of

reassortment in the vertebrate and/or invertebrate hostswill be minimised if the interval between therecommended vaccination period (late winter, earlyspring) and the BT season (especially summer) isrespected; this would make the incidence of co-circulatingvaccine and virulent wild-type viruses unlikely. Thenumber of possible reassortments in the case of BTV, whichhas ten segments, increases with the number of co-circulating serotypes (e.g. 1,024 for two serotypes [210] and59,049 for three serotypes [310]) (18). Reassortmentoccurred during the recent 1998-2005 BTV outbreaks inEurope (56).

The release and transmission of attenuated virus into theenvironment may also result in a reversion to virulencethrough reassortment with a wild-type strain (18).

The possibility that insects could acquire vaccine virus byfeeding on vaccinated animals and transmit it to sheep orcattle cannot be eliminated (18, 70). The minimumviraemia in infected animals necessary for successfulvaccine virus dissemination by biting midges remains to bedetermined, although Fu et al. (37) have shown that only12% of competent vector Culicoides sonorensis that were fedon blood containing 106-7 TCID50/ml were able to becomepersistently infected and to transmit the virus throughsaliva (42). However, the bite of only one infectedcompetent midge vector is sufficient to inducetransmission to susceptible ruminants (72, 73). Moreover,the vaccine virus serotype-2 was also detected recently inareas not included in the vaccination campaign (30). Thepossible circulation of this vaccine virus poses problemsthat have to be considered if vaccination with attenuatedstrains is the strategy of choice, particulary if the zonewhere vaccination is carried out is bordered by territoriesfree from disease/infection (30).

Lastly, attenuated vaccines were traditionally producedusing eggs, so allergy cases could not be excluded (2, 88).Currently they are produced in cell culture (18, 20) andthis risk decreases.

Inactivated virus vaccines

To avoid the problems listed above, inactivated vaccineshave been developed (16). Recently, two new inactivatedvaccines against BTV2 and BTV4 were developed andsimilar vaccines against other BTV serotypes are in the finalstages of development (94). However, limited reports arecurrently available on the effectiveness of these newvaccines in the field (15, 119).

Recombinant vaccines

Recombinant DNA technology has provided novelapproaches to developing intrinsically safe vaccines. This


technology involves the synthesis of immunogenic proteinsand particles that elicit highly protective immuneresponses. Protein engineering systems have been utilisedto synthesise individual bluetongue virus proteins andcore- (single coat) and viral-like (double coat) multiproteinstructures (CLPs, VLPs). These engineered particles mimicthe virus particles, but do not contain any genetic materials(35, 36, 78). These recombinant vaccines have been testedsuccessfully in vitro and under experimental conditions(83, 84, 107). Together with a suitable diagnostic test todetect antibodies against viral proteins not present in thevaccine a new BTV vaccine would allow the distinctionbetween vaccinated and infected animals (markervaccines) (20). In addition, deliberate release of anyorganism containing recombinant DNA into theenvironment should be subject to review and approval bycompetent authorities (33).

It is necessary to develop an inactivated vaccine or a vaccinebased on more advanced technology that would not onlyhave the potential to effectively control the disease but thatwould also facilitate trade, because the virus circulating inlive animals can be detected (117). Because of the smallcommercial market, vaccine manufacturers may need somepublic funding to achieve this objective (20).

Creating and developing an early warning system foremerging animal diseases One objective of the vaccination strategy in endemic BTareas is to reduce the intensity and duration of viraemia insusceptible animal populations (39).

To resort to vaccination requires a fast, argued andconcerted decision. Any delay in the detection of thedisease reduces the anticipated vaccine protection. Indeed,without early detection, emergence can pass unperceivedunless amplification of viral multiplication andtransmission reveals it. Detection is often too late from thepoint of view of risk control, particularly if the disease,before expressing itself clinically, passes through anincubation period allowing transmission to the sensitivepopulation by means of vectors (known or unknown)present in the environment (4) and via the sale of animalsoutside contaminated areas. The improvement ofidentification tools and an increase in the speed ofdetection are essential (25). The clinical approach to thedetection of emergence must be favoured because for anew disease no laboratory test is available to ensure itsdetection at the moment of emergence (87). In addition,for exotic diseases, the cost of specific analyses can beprohibitive in view of the need for immediate detection of

an emergence (e.g. the considerable cost of the quantitativereal-time reverse transcription polymerase chain reaction[Rt-RT-PCR] for the detection of the BTV).

Regulatory issues surroundingthe temporary authorisation ofanimal vaccination A marketing authorisation for a veterinary vaccine isgranted after an assessment of the quality, safety andefficacy of the product has been carried out in accordancewith legal standards (18, 27, 29, 48). In order to fulfil thenecessary criteria, data from all phases of the productdevelopment are evaluated against these key elements.Under the standard licensing process, the evaluationincludes:

– complete characterisation and identification of seedmaterial and ingredients

– laboratory and host animal safety and efficacy studies

– stability studies

– post-licensing monitoring of field performance (48).

This comprehensive evaluation may not be possible duringthe emergence of a new animal disease, but severalmechanisms exist to allow for the availability of productsin an emergency animal health situation, including:

– autogenous biologics

– conditional licenses

– experimental and emergency use authorisations

– the importation of products in use elsewhere in theworld

– pre-approved vaccine banks (Table V) (27, 29, 31, 47,48, 49).

Even when using the accelerated assessment procedureand conditional marketing authorisation procedure for anew medical product it can take up to five months toobtain an opinion concerning the granting of a Europeanauthorisation (26). Even in an emergency situation it canstill take a long time.

However, Member States are still authorised to usevaccines without a marketing authorisation in anemergency situation and, in this case, the EuropeanCommission must be informed (27, 29). This procedurehas been used successfully for bluetongue in theMediterranean endemic area (8, 21, 39, 119). Thevaccination strategy was mainly based on the use of themonovalent or polyvalent attenuated vaccines produced by


Onderstepoort Biological Products Ltd (South Africa) andto a lesser extent on the inactivated vaccine produced byMérial SAS in Lyons, France (8, 39, 119).

Epidemiological surveillance of BT in this vaccinationcontext requires the following tasks:

a) clear communication all along the process

b) a description of the prevalent epidemiological situation

c) the choice of an appropriate national response strategy

d) the choice of an appropriate vaccine

e) verification of the quality of the vaccine used

f) strict adherence to the vaccination protocol andinitiation and maintenance of a system allowingregistration, delivery and follow-up of vaccination

g) evaluation of the necessary level of vaccination coverage

h) monitoring, analysis and possible adjustment of fieldimplementation of the vaccination.

Each of these points is described in more detail below. Thisinformation is also useful for replacing the temporaryauthorisation by a complete authorisation as quickly aspossible.

Clear communication throughout the process

Communication is the rational process of conveying arepresentative picture of objects or situations when havingto perform a concerted action with several partners (51).Several levels of communication should be maintained (i.e.inside and outside of the epidemiological network).Concerning international trade, clear and immediatecommunication in the framework of animal diseasenotification is essential to limit the spread of the disease(e.g. the OIE World Animal Health Information System)and to ensure mutual trust between countries. Clearcommunication about uncertainties in all phases of thedecision process is also important.


Table V

Legislation governing the mechanisms which allow for the use of vaccines without marketing authorisation in the United States of

America and in the European Union in the case of an emerging disease

(adapted from 48)

Mechanism United States of America European Union

Approval of experimental products (a) Title 9 of the Code of Federal Regulations (b) Part 103.3 No specific legislation

(porcine reproductive and respiratory syndrome)

Use of autogenous biologics

Attenuated No specific legislation Directive 2001/82/EC, article 4 (27)

Inactivated Title 9 of the Code of Federal Regulations Part 113.113 (c) No specific legislation

(infectious salmon anaemia virus)

Conditional Product Licences (d) Title 9 of the Code of Federal Regulations Part 102.6 (West Nile virus) Regulation 2004/726/EC, article 39

(centralised procedure) (29)

Directive 2001/82/EC, article 26

(other procedure) (27)

Importation of products in use Title 9 of the Code of Federal Regulations Part 104 (rabbit calicivirus) Directive 2004/28/EC, article 8 (28)

elsewhere in the world (e)

Vaccine bank (f) No specific regulation (foot and mouth disease) Decision 2001/433/EC, article 3 (g) (bluetongue) (21)

Other (h) Title 9 of the Code of Federal Regulations Part 106.1 Directive 2004/28/EC, article 8 (28)

a) Experimental production, distribution and evaluation of biological products may be authorised prior to licensing under very specific circumstances

b) Title 9 of the Code of Federal Regulations (http://www.aphis.usda.gov/vs/cvb/html/cfr.html) (106)

c) According to this act, they are prepared from cultures of micro-organisms which have been inactivated and are non-toxic under certain circumstances

d) Conditional licences are authorised under very specialised circumstances to meet an emergency condition, limited market, local situation, or other special circumstance. Licences are issued

under an accelerated procedure which assures purity, safety and efficacy of the products involved

e) Permits for biological products imported into the considered country may be authorised for a variety of purposes. In each case, a separate veterinary biological product permit is required for

each shipment of biological product to be imported

f) No specific regulations exist for the creation and maintenance of a vaccine or seed bank

g) Under very specific circumstances, biological products may be exempted from one or more of the requirements. These circumstances are warranted if products will be used by or under the

supervision or control of the competent authority in the prevention, control or eradication of animal diseases in connection with an official programme or an emergency animal disease

situation, or an experimental use of the product by the Authority

h) In general, European legislation concerning the disease must specify the use of vaccination. In this case, the European Commission can propose the constitution of a vaccine bank with a

proposal for a European decision

Describing the prevalent epidemiological situation

A description of the true epidemiological situation is aprerequisite before any action can be undertaken, becausethis knowledge is needed to choose the appropriatestrategic option(s), including vaccination. This descriptionrequires the incorporation of detailed informationconcerning the following:

– suspected and confirmed clinical cases of BT (e.g.reason for the visit, date of suspicion, date of first infection,animal species involved, clinical signs, laboratorydiagnosis)

– outbreaks (e.g. species concerned, number and size of herds, location of herds, mortality rate, morbidity rate)

– vector (e.g. date and location of trapping, number of Culicoides identified)

– virus activity (e.g. date and location of sampling,number of animals sampled, number of animals at risk andnumber of animals seroconverted)

– boundaries and subdivision boundaries

– geography and climate (e.g. vegetative index,temperature, rainfall) (10, 41, 119).

Choosing an appropriate national response strategy

Risk assessment is a tool advocated by the World TradeOrganization in the context of trade policy (Agreement onthe Application of Sanitary and Phytosanitary Measures).The methodology can also be used to assist in the choice ofan appropriate national response strategy following anincursion of bluetongue (40). The choice of strategyshould be made after an independent, scientific andcollective assessment in which the range and magnitude ofconsequences of implementing or not implementing avaccination programme of all susceptible domesticlivestock in the affected regions is considered (scenarioanalysis). This methodology was used in Italy beforeinitiating vaccination of all susceptible domestic ruminantspecies in infected areas and areas surrounding them(protection zone). Under the relevant Italian conditions,the model predicted that at least 80% of susceptiblelivestock should be immunised for vaccination to beeffective (39). Such risk assessment should be conductedtaking into account current scientific knowledge, theparticular local situation and uncertainties about theparameters used in the model.

In addition, decision trees are often used to clarify the pathto appropriate vaccine usage. Analysis includes evaluationof several parameters, such as the probability of exposureto the infectious agent, the efficacy and safety of the

product, its availability and cost, and consequences ofvaccination. If a vaccinated animal cannot be differentiatedfrom an infected animal, further animal movementcontrols may need to be considered (33).

Choosing an appropriate vaccine

The choice of vaccine should be made taking into accountthe epidemiological situation of BT in the country orterritory concerned (e.g. BTV serotype(s)) and inaccordance with current knowledge about the advantagesand disadvantages of the bluetongue vaccination strategy(Table IV) and the availability on the world market of thevaccines being considered (94) (Table III). Informationconcerning the quantity of BT vaccines deemed necessaryin the case of emergency vaccination should be available inthe contingency plan of each Member State (23).

Verifying the quality of the vaccine used

The quality of the vaccine used must be verified. Results ofexperimental infection with the chosen vaccine andsubsequent challenge with the field strain BTV should becollected. Information concerning the safety and efficacy ofthe vaccine is required and help in the interpretation ofserology and virology results after vaccination may benecessary (45, 67).

Adhering to the vaccination protocol andmaintaining a system allowing registration,delivery and follow-up of vaccination

It is vital to strictly follow the manufacturer’s instructionsand to quickly administer the doses after reconstitution ofthe freeze-dried vaccine. The storage conditions of vaccineare very important (isotherm box): a rapid decrease ofinfectious virus titre is observed after a few hours atambient temperature (45). This observation could explainsome apparent vaccine failure in the field.

As with every veterinary medical product the traceability ofvaccine doses must be assured at local, regional andnational level. The following details must be entered into avaccine management information system, as without them itis not possible to correctly estimate vaccine coverage (39):

– vaccine serotype(s)

– vaccine batch numbers

– farm codes

– total numbers of animals on the farm

– numbers of target animals

– numbers of vaccinated animals by species

– vaccination date.


Evaluating the necessary level of vaccination coverage

It is important to evaluate the level of vaccination coveragethat should be attained to eradicate the disease. Anempirical evaluation gives a herd immunity threshold(HIT) value of 75% (Charles Nicolle’s law) but it has beenshown that HIT calculation should be based on theevaluation of the rate of spread of the disease measured bythe basic reproductive number R0, i.e. the average numberof secondary infections produced by one infectedindividual introduced into a fully susceptible population(1). Basically, if R0 <1, the disease cannot persist in apopulation. It can be shown that the proportion of animalsto be vaccinated in a naïve population must exceed 1–1/ R0

in order to reduce R0 to a value below 1. It is noted that forvector-borne diseases, several factors attributable to thevector will change the classical approach (e.g. biting rate,trophic preferences, survival rate, incubation period andvectorial competency, i.e. capacity for the virus to developin the vector). Consequently, even with high vaccinationcoverage, it is still possible that the virus will persist insmall areas or in reservoir animals. There is then a risk ofre-emergence when coverage declines (38).

The relationship between vaccination coverage of the targetpopulations and animal losses due to disease and viruscirculation must be analysed.

Monitoring, analysis and possible adjustment of field vaccination

In order to monitor the progress of the vaccinationcampaign in the infected zone and verify the immunestatus of vaccinated herds (coverage), a random sample ofvaccinated animals in each grid cell should be tested forantibodies (39).

All clinical suspicion must be investigated to confirmwhether or not BTV is present. In the case of viral detectionand isolation, serotyping of BTV is performed (e.g. byseroneutralisation test) to verify possible new strainintroductions into the territory. In this case, the vaccinationprogramme must be promptly adapted (119). If possible,an RT-PCR test should be carried out to differentiatebetween the wild type and vaccine viruses (8). In addition,strain genotyping permits the study of the molecularepidemiology of BT and the monitoring of possiblereassortment of genome segments between vaccine andfield viruses (7).

The vaccination programme must be maintained untilthere is proof that the virus is no longer circulating. Oncethe clinical signs disappear the absence of BTV circulationin the vaccinated populations must be verified. In order todo this, a longitudinal study of representative sentinel

herds in the risk area is performed. Because vaccinatedanimals are seropositive, subpopulations that are includedin the study must be unvaccinated animals (e.g. younganimals sampled when prophylactic treatment isadministered or in slaughterhouses). Blood samples fromsentinel herds should be collected using a statisticallybased sampling frame, with the frequency of collectiondepending upon the season and infection occurrence inthe area.

Entomological surveillance is performed by trappingmidges in areas of ecological importance in order tomonitor the spread and seasonal dynamics of Culicoidesspp. (39, 119). The presence of field BTV and vaccine virus(when using attenuated vaccine) must be investigated. Thepossibility that midges could acquire vaccine virus byfeeding on vaccinated animals and transmit it tounvaccinated animals should also be investigated, inparticular, with regards to territories that are free fromdisease/infection but border zones where vaccination iscarried out (30).

Conclusions andrecommendationsIn the case of an emerging disease (e.g. bluetongue), thedecision by national authorities to include temporaryauthorisation of a non-registered animal vaccine in diseasecontrol strategies requires scientific, economic, technical,social and risk analysis support. Advantages anddisadvantages of the vaccination option strategy (Table IV)should be taken into account, as well the regulatoryaspects (Table V), the biology and the epidemiology of thedisease, the structure and efficacy of the epidemiologicalnetwork and the economic and social impacts. Moreover,in the case of a zoonotic disease, factors affecting humansbecome a priority. Use of decision trees should also beencouraged.

For safety reasons inactivated or other moretechnologically advanced vaccines should be preferredbecause they have the potential not only to effectivelycontrol the disease but also to allow trade due to detectionof virus circulation in live animals. The development ofmarker vaccines is the correct choice for manufacturers,but national authorities and supra-national organisationsshould stimulate early development of these new vaccines(including bank vaccines) with the aim of delivering themquickly to reduce pathogen circulation in an emergingsituation. Listing and prioritisation of diseases of majorconcern (i.e. diseases which can have a severe impact onhuman/animal health or on the economy) should be thefirst step, for which an understanding of the accuracy ofthe estimation of the true prevalence of disease is essential.


The latter depends on the presence and quality of theepidemiologic network and on clearly and swiftly notifyingthe disease to the appropriate authorities (e.g. informationpromptly entered into the OIE World Animal HealthInformation System and into the Centralized InformationSystem for Infectious Diseases of the World HealthOrganization). The second step should be to find out aboutexisting patents and to develop a map showing thelocations of research laboratories, technology facilities andmanufacturers to be used by competent authorities in caseof emerging diseases. The third step should be to identifygaps and important weaknesses in available tools andsources. The fourth step should be to develop aproposition to focus research on priority animal disease soas to increase the knowledge base and product availabilityfor these diseases (94).

When applying this vaccination strategy several factorsshould be evaluated collectively, including:

– communication

– prevalent epidemiological situation

– response strategy to the disease

– appropriateness of the vaccine used

– adherence to vaccination protocol and maintenance of asystem allowing registration, delivery and follow-up ofvaccine

– level of vaccination coverage

– analysis and possible adjustment of field vaccination.

This information is useful for replacing the temporaryauthorisation with a complete authorisation.

It is also necessary to continuously adapt the vaccinationprogramme to the epidemiological situation. Thisadaptation requires the collaboration of all stakeholdersand needs to include independent and collective scientificadvice.

Finally, the concept of temporary authorisation can easilybe transposed for use with emerging zoonotic diseases andmay assist in improving relationships between differentVeterinary Services worldwide and it is an excellent way tobuild the necessary capacity to respond to emergingdiseases.

AcknowledgementsThe authors wish to thank P. Houdart (Federal Agency forthe Safety of the Food Chain) for help in accessing dataoriginating from the European Commission’s AnimalDisease Notification System and R. De Deken and M. Madder (Institute for Tropical Medicine) for use of thephoto of C. dewulfi.


Questions réglementaires liées à l’autorisation temporaire

de vacciner les animaux en situation d’urgence : l’exemple

de la fièvre catarrhale du mouton en Europe

C. Saegerman, M. Hubaux, B. Urbain, L. Lengelé & D. Berkvens

Résumé

L’autorisation de mise sur le marché des vaccins vétérinaires est accordée dès

lors que la qualité, l’innocuité et l’efficacité du produit ont été évaluées

conformément aux normes réglementaires. Cette évaluation comprend

la caractérisation exhaustive suivie de l’identification des semences et des

ingrédients utilisés, l’évaluation de la sécurité pour le laboratoire et pour

l’espèce hôte, ainsi que des études d’efficacité, un suivi après la mise sur le

marché et un contrôle des performances sur le terrain. Cette évaluation n’est

pas toujours réalisable en cas d’émergence d’une nouvelle maladie animale,

mais il existe plusieurs mécanismes permettant de disposer de produits dans des


Cuestiones de reglamentación en torno a la autorización

temporal de vacunación de animales en situaciones

de emergencia: el ejemplo de la lengua azul en Europa

C. Saegerman, M. Hubaux, B. Urbain, L. Lengelé & D. Berkvens

Resumen

Para autorizar la comercialización de una vacuna veterinaria es preciso que

previamente se hayan evaluado su calidad, inocuidad y eficacia conforme a la

normativa vigente. Ello comprende la descripción y caracterización completa del

material y los ingredientes de partida, los estudios de inocuidad para los

animales hospedadores y de laboratorio y los estudios de eficacia y estabilidad,

así como el control del rendimiento del producto sobre el terreno una vez

obtenida la licencia. Aunque todo este proceso puede resultar impracticable en

el momento en que se manifiesta una nueva enfermedad animal, existen varios

mecanismos para asegurar el suministro de productos en el curso de una

emergencia zoosanitaria, por ejemplo productos biológicos autógenos, licencias

condicionales, autorizaciones de uso experimental y de emergencia,

importación de productos utilizados en otras partes del mundo y bancos de

vacunas preaprobadas. Utilizando el ejemplo de la aparición de la lengua azul en

el Norte de Europa, los autores exponen las cuestiones de reglamentación que

se plantean respecto a la autorización temporal de vacunación de animales.

situations d’urgence zoosanitaire : autovaccins, autorisations de mise sur

le marché sous condition, autorisations limitées aux expérimentations ou aux

situations d’urgence, importation de produits utilisés en d’autres endroits du

monde, banques de vaccins pré-enregistrés. Les auteurs décrivent

les questions réglementaires liées à l’autorisation temporaire de vacciner les

animaux, en prenant l’exemple de l’émergence de la fièvre catarrhale du mouton

en Europe. Plusieurs conditions doivent être réunies avant de délivrer une

autorisation temporaire : le vaccin doit être à virus inactivé afin d’empêcher tout

risque de réversion vers la virulence ou de réassortiment entre les souches

vaccinales et/ou les souches sauvages du virus de la fièvre catarrhale du

mouton ; les décisions en la matière doivent être justifiées scientifiquement et se

fonder sur une analyse du risque ; les animaux susceptibles ayant été vaccinés

doivent être rigoureusement recensés ; les protocoles de vaccination doivent

être connus et respectés ; un dispositif doit être en place pour l’enregistrement,

l’administration et le suivi de la vaccination, ainsi que pour le suivi, l’analyse et

d’éventuelles corrections dans l’utilisation de la vaccination sur le terrain. Cette

autorisation temporaire doit être remplacée aussi rapidement que possible par

une autorisation régulière.

Mots-clés

Autorisation temporaire – Maladie émergente – Question réglementaire – Santé animale

– Vaccin – Vaccination.

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Palabras clave

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International harmonisation

of regulatory requirements

M. Holmes (1) & R.E. Hill (2)

(1) Australian Pesticides and Veterinary Medicines Authority, PO Box E240, Kingston ACT 2604, Australia

(2) Center For Veterinary Biologics, Animal and Plant Health Inspection Service, United States Department of

Agriculture, 510 S. 17th Street, Suite 104, Ames, IA 50010, United States of America

Summary

The International Cooperation on Harmonisation of Technical Requirements for

Registration of Veterinary Medicinal Products (VICH) was formed in April 1996

and is a programme of collaboration between regulatory authorities and the

animal health industries of three world regions: the European Union, Japan and

the United States of America. Two other regions, Canada and Australia/New

Zealand, have observer status.

The principal goal of VICH is to harmonise technical data requirements of

participating regulatory authorities before granting marketing authorisation or

registration.

VICH has finalised six guidelines on the technical requirements for marketing

authorisation/registration of biological products. These guidelines have been

fully implemented in the regions. Three more technical guidelines are under

development by two expert working groups.

VICH has also finalised a guideline which specifically deals with

pharmacovigilance and veterinary medicinal products, including biological

products. A further four guidelines relating to pharmacovigilance are under

development by an expert working group.

Keywords

Harmonisation – Mycoplasma contamination – Pharmacovigilance – Regulatory

requirements – Residual formaldehyde – Residual moisture – Reversion to virulence –

Specification – Stability testing – Vaccine – VICH.

IntroductionUnder the auspices of the World Organisation for AnimalHealth (OIE), three main regions (the European Union[EU], the United States of America [USA], Japan) and twoobserver regions (Canada and Australia/New Zealand) seekto harmonise regulatory data requirements for marketingauthorisation for pharmaceutical and biological veterinarymedicinal products (VMPs). This article gives an update onthe present situation for biologicals and outlines futureperspectives.

Many of the world’s veterinary authorities require VMPs(biologicals and pharmaceuticals) to be granted marketingauthorisation before the products can be distributed intheir countries. In some countries the alternate term‘registration’ is used. This degree of regulatory control isconsistent with one of the missions of the OIE: ‘To improve

the legal framework and resources of national VeterinaryServices’. International harmonisation objectives areconsistent with improving this framework.

The role of the InternationalCooperation on Harmonisationof Technical Requirements forRegistration of VeterinaryMedicinal Products

The International Cooperation on Harmonisation ofTechnical Requirements for Registration of VeterinaryMedicinal Products (VICH) was formed in April 1996 and

is a programme of collaboration between the regulatoryauthorities and the animal health industry of the EU, Japanand the USA. Canada and Australia/New Zealand haveobserver status at VICH, and participate at both theSteering Committee and Expert Working Group levels. TheOIE participates as an associate member in the VICHprocess, and assists by supporting and disseminating theoutcomes worldwide.

VICH provides a forum for a constructive dialoguebetween regulatory authorities and the animal healthindustry on harmonising the regulatory technicalrequirements for VMPs within the VICH regions.

The objectives of VICH are to:

– establish and implement harmonised regulatoryrequirements for VMPs in the VICH regions which meethigh quality, safety and efficacy standards and minimise theuse of test animals and the costs of product development

– provide a basis for wider international harmonisation ofregistration requirements

– monitor and maintain existing VICH guidelines, takingparticular note of the International Conference onHarmonisation of Technical Requirements for theRegistration of Pharmaceuticals for Human Use (ICH)work programme, and where necessary, update these VICH guidelines

– ensure efficient processes for maintaining andmonitoring consistent interpretation of data requirementsfollowing the implementation of VICH guidelines

– provide technical guidance (by means of a constructivedialogue between regulatory authorities and industry) thatenables an effective response to be made to significantemerging global issues and scientific developments that impact on regulatory requirements within the VICH regions.

VICH also provides guidance to members on the technicalrequirements for authorisation/registration of VMPs inorder to protect public health, animal health, animalwelfare and the environment.

VICH achieves its objectives through the development ofguidelines by expert working groups. These groups arecomposed of recognised experts on the topic and are task-oriented, with their primary objective being thedevelopment of a draft guideline that will be released forconsultation by the Steering Committee, and subsequentlyimplemented by the regulatory authorities in each of the regions.

Members of expert working groups and the VICH SteeringCommittee work towards the harmonisation of technicalrequirements by way of consensus in accordance with

established procedures. All guidelines are published on theVICH website (http://www.vichsec.org).

To finalise guidelines, VICH uses a nine-step process whichincludes:

– formation of an expert working group to prepare draftsof the guideline

– approval by the VICH Steering Committee for publicrelease of draft guidelines for comment

– release of the final guideline to regulatory authorities forimplementation

– revision of guidelines.

To date, VICH has finalised 36 guidelines. Eight guidelinesare at advanced stages of development and consultation,six guidelines are at an early stage of development and afurther five topics are potential future guidelines.

VICH currently categorises its working groups into fivebroad areas:

– quality

– pharmacovigilance

– target animal safety

– biologicals quality monitoring

– metabolism and residue kinetics.

Each working group may work on one or several VICHguidelines.

Guidelines for veterinarybiological productsFive VICH guidelines (GL), all of which are available fromthe VICH website, are relevant to the technicalrequirements for marketing authorisation/registration ofVMPs that have been developed and implemented in eachof the member and observer regions. One more technicalguideline is under development by an expert workinggroup.

One guideline relevant to pharmacovigilance has beenfinalised and an additional four pharmacovigilanceguidelines are under development by an expert workinggroup.

Stability testing: GL3 and GL17

The stability of vaccines and biologicals must be determined to ensure that the storage conditions underwhich they are designed to be held are appropriate.


The aim is to determine the optimum storage conditions(such as ideal temperature and protection from light)which will maintain the efficacy of the product up to theend of its shelf life.

GL3: Stability testing of new veterinary

drug substances and medicinal products

GL3 is a generic guideline for all VMPs. This guidelinedescribes the core stability data package required for newdrug substances and products. The guideline provides ageneral indication of the requirements for stability testing,but leaves sufficient flexibility to encompass the variety ofdifferent practical requirements necessary for specificscientific situations and for the particular characteristics ofthe materials being evaluated.

GL17: Stability testing of new

biotechnological/biological

veterinary medicinal products

While GL3 applies in general to new biotechnological/biological products, GL17 recognises that specificbiotechnological/biological products may havedistinguishing characteristics, the stability of which shouldbe evaluated using a well-defined testing programme thatcan confirm that the product’s efficacy would bemaintained during the intended storage period. Thus,GL17 covers the generation and submission of stabilitydata for products such as cytokines, growth hormones andgrowth factors, insulins, monoclonal antibodies, and thosevaccines which consist of well-characterised proteins orpolypeptides even when chemically synthesised.

GL17 provides guidance on:

– selection of batches for the generation of stability datafor submission to the regulatory authority

– selection of the assay or parameter that profiles thestability characteristics of the product

– storage conditions for stability studies, such astemperature and humidity

– studies on stability under conditions of heat stress, suchas may occur during transport

– stability after reconstitution and in-use stability ofmultiple-use vials.

Good clinical practice: GL9

This VICH guideline is intended to be an internationalethical and scientific quality standard for designing,conducting, monitoring, recording, auditing, analysingand reporting clinical studies that evaluate veterinaryproducts, including biological products. Adherence to this

guideline provides public assurance that the clinical studydata are reliable and that due regard has been given toanimal welfare and to the protection of the personnelinvolved in the study, the environment and the human andanimal food chains.

Testing for residual formaldehyde: GL25

Many inactivated veterinary vaccines, particularlybacterins, contain residual levels of formaldehyde. It is important to determine the residual level offormaldehyde to:

– help assure product safety

– ensure that the product will not inactivate otherproducts used in combination

– help assure that the product remains active throughoutits shelf life

– ensure that any clostridial toxoids will be antigenic and safe.

GL25 is a guideline for the general requirements forresidual formaldehyde testing. The guideline allows for flexibility for other testing methods based on specificscientific situations or the characteristics of the targetmaterial.

Testing for residual moisture: GL26

Freeze-dried veterinary vaccines always contain somewater, commonly known as residual moisture (RM). It isimportant to determine the level of RM in final productsbecause a satisfactory test gives assurance of an adequateshelf life and that the manufacturer’s freeze-dry cycle wasproperly controlled.

The RM test should confirm that moisture level isconsistently within the manufacturer’s specification.

GL26 is a guideline on the general requirements for RMtesting. The guideline allows for flexibility for other testmethods based on specific scientific situations or thecharacteristics of the target material.

Guidelines relevant to

pharmacovigilance: GL24, 29, 30, 35, 42

Pharmacovigilance is the process of monitoring theongoing safety and efficacy of marketed products after theyhave received marketing authorisation/registration.Pharmacovigilance provides essential feedback to productmanufacturers and also to regulatory authorities.

Manufacturers need pharmacovigilance data for purposesof product warranty, product improvement and future


product development. Regulatory authorities needpharmacovigilance data to provide feedback on theintegrity of the regulatory process, and more importantly,to provide ongoing assurance that the products are safe foranimals and humans.

Four of these guidelines are currently in the advancedstages of final drafting and consultation before beingreleased for adoption by regulatory authorities. Together,the five guidelines form a suite which provides acomprehensive framework for submitting, receiving andanalysing adverse event reports (AERs), using uniformterminology.

Testing for Mycoplasmaspp. contamination: GL34

It is important that biological products for veterinary useare free of contamination with Mycoplasma spp. to helpassure consistency of production and final product safety.Mycoplasma contaminants may be introduced into cellculture and in ovo-origin biological products through themaster seeds, the master cell seed (stock) or startingmaterials of animal origin, and in processing of biologicalmaterials during passage and product assembly. Therefore,it is necessary to demonstrate through testing thatMycoplasma are not present in the final product, workingseeds and cells and harvests, or starting materials such asthe master seed, master cell seed, or ingredients of animal origin.

GL34 gives guidance on the stages of manufacture to betested and test procedures to detect the presence ofMycoplasma contamination. GL34 is currently in anadvanced stage of final drafting and consultation beforebeing released for adoption by regulatory authorities.

Specifications – test procedures and acceptance criteria for newbiotechnological/biological veterinary medicinal products: GL40

A specification is defined as a list of tests, references toanalytical procedures, and appropriate acceptance criteriasuch as numerical limits, ranges, or other criteria for thetests described. A specification establishes the set of criteriato which a veterinary product should conform to beconsidered acceptable for its intended use. Conformanceto specification means that the product, when testedaccording to the listed analytical procedures, will meet theacceptance criteria. Specifications are critical qualitystandards that are proposed and justified by themanufacturer and approved by regulatory authorities asconditions of approval.

Specifications are one part of a total control strategydesigned to ensure product quality and consistency. Otherparts of this strategy include thorough productcharacterisation during development (upon which many ofthe specifications are based), adherence to goodmanufacturing practices, a validated manufacturingprocess, raw materials testing, in-process testing, stabilitytesting, etc.

Specifications are chosen to confirm the quality of the drugsubstance and medicinal product rather than to establishfull characterisation and should focus on those molecularand biological characteristics found to be useful inensuring the safety and efficacy of the product.

Examination of live veterinary vaccines in target animals for absence of reversion to virulence: GL41

The absence of reversion to, or increase in, virulence is afundamental requirement for all live vaccines. Livevaccines replicate in the animal and stimulate a usefulimmune response. Live vaccines generally cannot becompletely characterised by chemical and physical testsalone. For these reasons, a test for absence of reversion tovirulence is of critical importance.

GL41 is a draft guideline which gives guidance for studiesto be conducted on the master seed, by passaging insuitable animals, to check for reversion to virulence. Ifavailable data or assessment indicate a substantial risk thatthe test organism may revert to or increase in virulence,additional studies may be required to provide furtherinformation on the organism.

Target animal safety testing for live and inactivated vaccines: GL44

This important guideline is currently under developmentby an expert working group. It is a contribution towardsinternational harmonisation and standardisation ofmethods used to evaluate the target animal safety of newveterinary vaccines. The guideline is designed to aidsponsors in preparing protocols for target animal safetystudies conducted under laboratory conditions and inrelated field studies.

ConclusionThe regulation by national veterinary authorities of thequality and safety of veterinary vaccines and biologicalsmakes a significant contribution to the ongoing usefulnessof vaccines and biologicals in the prevention and treatment


of animal disease. However, regulation by itself has limitedeffect unless the manufacturing companies manufactureproduct to the highest quality standards, and providecomprehensive data dossiers for evaluation by theregulatory authorities.

The value of the VICH guidelines lies in their jointdevelopment by technical experts from industry, academiaand regulatory authorities. This collaboration providesguidance documents consistent with current scientific

methods, and methods recognised worldwide as thestandard for testing and evaluating VMPs. The VICHguidelines have made a significant contribution towardsinternationally harmonised technical standards forveterinary vaccines and biologicals.


Harmonisation internationale des dispositions réglementaires

M. Holmes & R.E. Hill

Résumé

La Coopération internationale sur l’harmonisation des exigences techniques

applicables à l’enregistrement des médicaments vétérinaires (VICH) a été créée

en avril 1996 afin d’organiser la collaboration entre les autorités réglementaires

et l’industrie pharmaceutique en santé animale dans trois régions du monde :

l’Union européenne, le Japon et les États-Unis d’Amérique. Deux autres régions

ont un statut d’observateur : le Canada et l’Australie/Nouvelle-Zélande.

La VICH a pour principal objectif d’harmoniser les cahiers des charges

techniques imposés par les autorités réglementaires en vue de l’autorisation de

mise sur le marché ou de l’enregistrement d’un médicament vétérinaire.

La VICH a préparé six lignes directrices sur les exigences techniques relatives à

l’autorisation de mise sur le marché/enregistrement des produits biologiques.

Ces lignes directrices sont intégralement appliquées dans les trois régions. Trois

autres lignes directrices sont en préparation, sous la responsabilité de deux

groupes de travail spécialisés.

La VICH a également produit une ligne directrice sur la pharmacovigilance et les

médicaments vétérinaires, y compris les produits biologiques. Quatre nouvelles

lignes directrices liées au thème de la pharmacovigilance sont en préparation

sous la conduite d’un groupe d’experts.

Mots-clés

Contamination par Mycoplasma – Dispositions réglementaires – Épreuve de stabilité –

Harmonisation – Humidité résiduelle – Pharmacovigilance – Résidu de formaldéhyde –

Réversion vers la virulence – Spécification – Vaccin – VICH.


Armonización internacional de los requisitos reglamentarios

M. Holmes & R.E. Hill

Resumen

La Cooperación Internacional para la Armonización de los Requisitos Técnicos

para el Registro de Medicamentos Veterinarios (VICH), que echó a andar en abril

de 1996, es un programa de colaboración entre las instancias reglamentarias

y la industria zoosanitaria de tres regiones del mundo: la Unión Europea, Japón

y los Estados Unidos de América, más otras dos regiones, Canadá y

Australia/Nueva Zelanda, que participan en calidad de observadoras.

La VICH tiene por objetivo primordial armonizar los requisitos de datos técnicos

que imponen las instancias normativas participantes para registrar un producto

u otorgar licencia de comercialización.

La VICH ha elaborado seis directrices sobre requisitos técnicos para autorizar la

comercialización o registrar productos biológicos, y todas ellas se han aplicado

integralmente en las tres regiones citadas. Ahora mismo hay dos grupos de

expertos que están elaborando otras tres directrices técnicas.

La VICH también tiene ya ultimada una directriz dedicada específicamente a la

farmacovigilancia y los medicamentos veterinarios incluídos los productos

biológicos. Un grupo de expertos trabaja actualmente para elaborar otras cuatro

directrices sobre farmacovigilancia.

Palabras clave

Armonización – Contaminación por micoplasma – Especificación – Farmacovigilancia –

Formaldehído residual – Humedad residual – Prueba de estabilidad – Requisitos

reglamentarios – Reversión a la virulencia – Vacuna – VICH.


Authorisation within the European Union

of vaccines against antigenically variable viruses

responsible for major epizootic diseases

D.K.J. Mackay

European Medicines Agency (EMEA), 7 Westferry Circus, London E14 4HB. Email:

[email protected]

The views expressed in this article are the personal views of the author and should not be taken to represent

the position of the EMEA, the Committee for Medicinal Products for Veterinary Use, or the European

Commission

Summary

Antigenically variable viruses are responsible for some of the most contagious

and economically important diseases that affect domestic livestock. The serious

consequences of such diseases in terms of economic loss, and human and

animal health, were clearly demonstrated by recent epizootics of foot and mouth

disease, and outbreaks of avian influenza and bluetongue in the European Union

(EU). For such diseases, government authorities need to be able to respond, if

appropriate, by making use of vaccines that are suited to the epidemiological

situation. The current EU regulatory framework is not well adapted for approval

and maintenance of vaccines where the antigens included have to be chosen to

reflect the epidemiological need. An extensive revision of the technical

requirements for authorisation of veterinary medicinal products within the EU is

currently underway. Additionally, a major revision of the regulations that control

how such authorisations are kept up-to-date is about to start. This provides an

ideal opportunity to introduce into EU legislation the concept of the ‘multistrain

dossier’ whereby a potentially large number of approved strains may be included

within a marketing authorisation and the final vaccines may be blended to

include strains according to need. In addition, new strains may be added onto

the marketing authorisation by means of a rapid regulatory procedure should

new antigenic variants actually or potentially threaten the EU.

Keywords

Authorisation – Avian influenza – Bluetongue – European Union – Foot and mouth

disease – Licensing – Vaccine.

IntroductionThe recent experience of Europe with respect to foot andmouth disease (FMD), avian influenza (AI) and bluetongue(BT) has raised the issue of vaccination against theseantigenically variable viruses in the mind of the generalpublic and of those responsible for controlling these highlycontagious animal diseases. This article discusses thereasons why there is a need for such vaccines to be

authorised, the factors that currently act as a disincentiveto authorisation and the proposals currently underdiscussion aimed at promoting their authorisation.

The latter part of the 20th Century saw the introduction ofregulatory systems to ensure the consistent quality ofmedicines in all of the major developed markets of theworld, first for human medicines and subsequently forveterinary medicines. The main driver for developing these

regulatory requirements was the increasing recognition bygovernments and consumers of the need for medicines tobe safe, of high and consistent quality, and efficacious.These requirements inevitably lead to increased costs formanufacturers both to meet the required standards and toput in place suitable systems of quality assurance. Thesecosts can fairly readily be recouped in the case of productswith a substantial and predictable market. In contrast, inthe case of diseases which are exotic to the country orregion concerned, or are subject to successful eradicationprogrammes, there is little incentive for industry to investin meeting the costs of authorising a vaccine for which theuse and financial return are uncertain. On the other hand,in the case of such diseases, the consequences of notvaccinating are frequently not acceptable due to the risk ofuncontrolled spread. Therefore, veterinary authorities willoften seek to obtain and use an appropriate vaccine,whether or not it has met the usual regulatoryrequirements of the country or region concerned.

In addition to the financial disincentives, the highlycomplex antigenic nature of the viruses responsible forFMD, AI and BT presents particular problems in terms ofauthorising vaccines. Each of these viruses exist as multipleserotypes wherein the definition of a serotype is thatvaccination against, or previous infection with, oneserotype does not provide protection against otherserotypes. Furthermore, in the case of FMD and AI, theextent of variation within each serotype is sufficiently greatthat not all strains within a serotype will cross-protectagainst each other. Each virus has its own particularmechanism by which it maintains antigenic diversity. Inthe case of FMD virus, this phenotypic diversity is theresult of the quasispecies nature of small ribonucleic acid(RNA) viruses. The inherent imprecision of the replicationmechanism of the genome results in the constantproduction of progeny viruses that are slightly differentfrom their parent. Added to this, simultaneous infectionwith more than one strain and/or serotype of FMD virus isnot uncommon and can lead to recombination. In the caseof BT virus there are 24 serotypes and the virus has asegmented genome. Again, co-circulation of differentserotypes is normal in endemic areas, thereby creatingideal conditions for reassortment. In the case of AI, as withother influenza viruses, antigenic drift results in theconstant evolution of the antigenic nature of the prevalentstrains in a population and antigen shift, as a result ofreassortment, can result in the production of antigenicallynovel viruses with the consequent potential for pandemicspread.

It is not the intention of this paper to cover in detail themechanisms whereby these three viruses maintainantigenic diversity. What is relevant is to emphasise thefollowing features which these viruses have in commonthat present particular challenges from a regulatoryperspective:

– they are antigenically complex and there is therefore a need to have in place a wide range of authorised vaccinestrains

– there is a constant need to monitor the field situation toensure that vaccine strains remain relevant and to have inplace a mechanism to change strains rapidly whenrequired

– in each case there is the potential for the rapidintroduction, or development, of antigenically novelvariants against which existing vaccine strains are ineffective and which therefore require thedevelopment, validation, authorisation and introductioninto manufacturing of new master seed viruses in as shorta space of time as possible.

Why authorise vaccines?In view of the expense and administrative complexity thatauthorisation of vaccines introduces, it is important tounderstand why it is desirable that vaccines are authorised.As indicated in the introduction, authorisation providesassurance to the customer as to the quality, safety andefficacy of the product. In the case of vaccines used undernational authority control, the customer can be said to bethe national authority that purchases the vaccine from themanufacturer. National authorities see authorisation as ameans of assuring the efficacy of the product withoutthemselves having to conduct the necessary trials. In thecase of all three diseases under consideration, experimentaltrials involving challenge with live viruses can only beconducted under highly contained conditions. The exactcategory of containment depends on the nature of theagent concerned but is the highest level for animals in thecase of FMD virus and the highest level for both man andanimals in the case of H5 highly pathogenic avianinfluenza viruses. Such facilities are extremely expensive tobuild and maintain and access to them is therefore limitedon both logistical and financial grounds. For these reasons,as well as to reduce the need for testing in animals, it ishighly advantageous if vaccines are authorised by anindependent body based on compliance to agreedstandards resulting from accumulated scientific data,thereby reducing or replacing the need for exhaustive andexpensive tests in animals.

In the case of compulsory vaccination campaigns, nationalauthorities have an obligation to provide the best possibleassurance of the quality of the products used, since thestockholders have no choice as to whether or not theiranimals are vaccinated. In this respect, the additionalassurance that is provided by independent assessment ofthe quality and safety of the products is extremely helpfulin terms of reassurance both to the stockholders and to the


consumers of products from vaccinated animals. Recentexperience with both FMD and AI has shown a reluctanceon the part of some wholesalers and retailers to acceptproducts from vaccinated animals, resulting in them optingto source produce from other, unvaccinated animals. Muchof this reluctance results from ignorance of commonagricultural practices and can be countered by educationcampaigns. However, the use of authorised vaccinesprovides an added level of assurance as to the safety of thevaccines themselves, and of products from animals treatedwith them, which is useful when seeking the support ofretail organisations, stakeholder groups and independentfood standards agencies.

The challenges of authorisingvaccines against antigenicallyvariable virusesAuthorisation of ‘conventional’ vaccines provides a highdegree of regulatory certainty by permitting manufacturersto produce a product in approved premises according toGood Manufacturing Practice (GMP) and in line with theterms of a marketing authorisation (the EU term‘marketing authorisation’ is used throughout this paper,but in other regulatory areas such an approval may betermed a ‘product licence’ or ‘permit’). The marketingauthorisation specifies the raw materials that are to beused, the manufacturing method to be followed and the in-process and final tests that must be performed todemonstrate the quality and consistency of the finalproduct. A variation procedure must be approved by thelicensing authority before any changes can be made to theterms of the authorisation. Thus, in the case of a vaccine,the authorisation defines a fixed formulation consisting ofspecified amounts, or limits, of one or more antigensderived from pre-determined master seeds blended withspecified excipients and/or adjuvants.

This definition is not suited to vaccines against highlyantigenically variable viruses for a number of reasons.Manufacturers will generally blend vaccines according tothe epidemiological situation of the region in which theyare to be used. Thus, vaccines may contain antigensderived from one or more of a wide range of master seedviruses. Under normal regulatory requirements,manufacturers would be required to demonstrate the safetyand efficacy of each antigen, both individually and incombination, something which is clearly impractical whenmanufacturers may use any combination of up to 20 ormore master seeds. Testing the safety, efficacy, onset andduration of immunity for each of 20 strains as monovalentvaccines would occupy a high containment unit for severalyears. Add to this trials for bi-, tri- or quadrivalentvaccines, and the myriad combinations of possible

antigens, and it is immediately apparent that a newapproach is required to the authorisation of such vaccines.Under existing legislation, inclusion or substitution of anew strain into an existing vaccine would require a newauthorisation which could take up to 210 days forapproval. Again, a new approach is required as this isclearly unacceptable for diseases such as FMD, BT and AIwhere there is the potential for pandemic spread. TheCommittee for Medicinal Products for Veterinary Use(CVMP) of the European Medicines Agency startedconsidering this issue following the outbreak of FMD inthe United Kingdom (UK) and several other EuropeanUnion (EU) Member States in 2001, ultimately resulting inthe publication of the Position Paper on Requirements forVaccines against Foot-and-Mouth Disease (EMEA/CVMP/775/02 – adopted June 2004) (3) and the Guideline onRequirements for Vaccines for Use in Birds against AvianInfluenza (4).

Exceptional authorisation and use of vaccines without an authorisationTo date, the solution to these problems has been sought ona Member State level by using unauthorised vaccines orvaccines authorised under exceptional circumstances.Article 8 of Directive 2001/82/EC (as amended byDirective 2004/28/EC) (5) permits Member States to useimmunological medicinal products without anauthorisation ‘in the event of serious epizootic disease’.Article 7 of the same Directive permits Member States touse products authorised in another Member State ‘wherethe health situation so requires’, but this is of little usewhere the necessary vaccines are not authorised in anyMember State. Article 26 (3) of Directive 2001/82/EC fornationally authorised products, and Article 39 (7) ofRegulation 726/2004 for centrally authorised products (6),provide for authorisation under exceptional circumstancesfor ‘objective and verifiable reasons’, such as the need tocombat outbreaks of contagious, exotic disease and whereit is not possible to conduct all of the usual tests (seebelow). In such circumstances some of the usualrequirements for authorisation can be made into specificobligations to be carried out by the marketingauthorisation holder as a condition of receiving anauthorisation. These take the form of commitments toconduct studies or provide additional data to an agreedtimetable after the authorisation has been issued, therebyallowing a more rapid authorisation procedure. However,such authorisations do not represent a real solution to theproblem as they are reactive by nature and, due to thenecessity for an annual review, burdensome inadministrative terms, making them expensive both fornational authorities and manufacturers.


Routes to authorisation of medicinal products withinthe European Union

There are two main routes to authorisation of medicinalproducts within the EU. In the centralised procedure,applicants apply to the European Medicines Agency(EMEA) for an application to be considered by the CVMP.Following a positive opinion from the CVMP, the EuropeanCommission issues a decision granting a marketingauthorisation that is valid in all 27 Member States of theEU as well as Norway, Iceland and Liechtenstein. In thenational, mutual recognition or decentralised procedures,national marketing authorisations are issued in eachMember State in which authorisations are sought and theCoordination Group for Mutual Recognition andDecentralised Procedures (veterinary) (CMDv) ensures thatthe authorisations issued are harmonised. Following thereview of EU pharmaceutical legislation in 2001, severalamendments were introduced to promote authorisation ofvaccines against major epizootic diseases through thecentralised procedure. Commission Regulation (EC)726/2004 (6) opens up the scope of the centralisedprocedure to any immunological veterinary medicinalproduct that is used for the treatment of animal diseasesthat are subject to Community prophylactic measures. Thistherefore includes conventional, inactivated vaccinesagainst FMD, BT and AI. In addition, it is obligatory forany vaccine produced using recombinant deoxyribonucleicacid (DNA) technology to be authorised through thecentralised procedures, including recombinant or vectorvaccines against these three diseases. Authorisation ofvaccines to be used as part of Community campaignsthrough the centralised procedure has many advantagesfrom an EU perspective in that a single authorisationpermits an identical product of proven quality to beavailable for use in all Member States.

As mentioned above, vaccines may be authorised underexceptional circumstances through both the centralisedand national procedures. An authorisation underexceptional circumstances permits Member States and theCommission to issue authorisations subject to specificobligations. This provision is necessary, for example, toexempt the manufacturer from having to conduct fieldtrials before authorisation in view of the fact thatcommunity legislation prohibits vaccination against exoticdiseases except as part of an approved vaccinationcampaign. Instead, the marketing authorisation holder willbe required to put in place a system for enhancedpharmacovigilance (i.e. detection of side effects andadverse reactions) in the event that the product is usedwithin the EU. In addition, the revised legislation providesfor an accelerated assessment as part of the centralised

procedure of up to a maximum of 150 days for products ofmajor importance in terms of animal health. Theprovisions for accelerated assessment and exceptionalauthorisation were both used successfully in 2006 to grantcentral authorisations within a total period of four monthsfor two vaccines against AI so that authorised vaccineswere available throughout the Community in time for theperiod of increased risk in the autumn.

The need for a specificapproach to antigenicallyvariable viruses: the concept ofthe ‘multistrain dossier’Whilst all of these measures are certainly helpful inpromoting the authorisation and use of vaccines againstdiseases such as FMD, BT and AI within the EU, they arenot, in themselves, likely to act as a major incentive toauthorisation. The regulatory model of ‘one authorisation= one fixed formulation’ does not adequately take intoaccount the complex and varied requirements for vaccinesagainst these diseases. The technical requirements thatmust be met for a marketing authorisation to be initiallygranted are defined in Annex 1 to Directive 2001/82/EC(5). The requirements for varying a marketingauthorisation once granted are defined in the variationsregulations (Commission Regulations (EC) No. 1084/2003& 1085/2003) (1, 2). Both of these sets of requirements arecurrently being revised by the Commission in consultationwith Member States and this provides an ideal opportunityto introduce a more flexible approach to authorisation ofantigenically variable viruses. This approach has beentermed the ‘Multistrain Dossier’ concept.

The detailed guidance on how such a concept couldoperate in practice has yet to be elaborated. The followingproposals develop the approach outlined in the CVMPPosition Paper on Requirements for Vaccines against Foot-and-Mouth Disease and offer one potential solution. In thisproposal, the authorisation for a multistrain dossier wouldinclude a number of defined, approved master seed virusesand would specify the maximum number of antigensderived from these master seeds that may be incorporatedinto a vaccine blend. Within these parameters, themarketing authorisation holder may then choose the actualnumber and type of antigens to be blended in a particularbatch for a particular epidemiological situation. Theamount of each antigen blended would be constrainedwithin limits agreed with the regulator based on safety andefficacy data submitted at the time of approval of themaster seed for the authorisation. This approach pre-supposes that all of the antigens on the authorisation are


essentially similar in all respects other than their antigenicnature. This assumption is only valid where manufacturersoperate to strict standards of GMP, thereby tightlycontrolling all aspects of the manufacturing process suchthat there is a high reproducibility of production, bothbetween different batches of the same antigen and betweendifferent antigens. This approach is only likely to befeasible for modern generation vaccines in which theantigen is well defined and, preferably, purified beforeblending. Provided this assumption is valid, it is thenpossible to extrapolate certain parameters betweenantigens, reducing or removing the need to repeat studiesfor all antigens, and all combinations of antigens, includedwithin the authorisation. These parameters include safety,in terms of inducing adverse local and systemic reactions,and immunogenicity, in terms of onset, extent andduration of immunity. To demonstrate that extrapolation isvalid, manufacturers need to supply appropriate data onbatch production and testing records. These data shouldshow the expected consistency of production and of resultsfor in-process and final testing of stability, antigen content,batch safety and potency.

Further work is required within the regulatory communityto define more precisely what data is required to accept anew master seed virus, and antigen produced from thatmaster seed, onto the authorisation for a multistraindossier, both at the time of authorisation and subsequently.Different requirements may apply, particularly in relationto testing for the presence of extraneous agents, dependingon the urgency of the situation and therefore whether ornot authorisation is sought under exceptionalcircumstances (see section on ‘Exceptional authorisationand use of vaccines without an authorisation’ above). Intechnical terms, to add a new master seed, theauthorisation holder should demonstrate that antigen fromthe new seed can be produced using the method ofproduction described in the dossier. The results of in-process and final product tests should demonstrateequivalence of the new antigen to already approvedantigens. In order for the multistrain dossier approach towork in practice there needs to be a legislative mechanismthat allows new strains to be added to an authorisationmore quickly than is possible under the current ‘lineextension’ procedure, which can take up to 210 days. Thiscould either take the form of a shortened line extensionprocedure or, preferably, an amendment to the legislationwhich allows the addition of a strain onto a multistrain

dossier through a rapid variation procedure. An analogoussituation already exists for human influenza vaccineswhereby a change of strain to reflect the prevailingepidemiological situation is completed by means of avariation procedure within a maximum of 60 days.Furthermore, there is a legal provision for immediateacceptance of a variation in pandemic situations forinfluenza or other pandemic human viruses (Articles 7 and8 of Commission Regulations (EC) No. 1084/2003 and1085/2003) (1, 2). There is clearly value in adopting asimilar approach on the veterinary side as part of themeasures necessary to make the multistrain dossierapproach a feasible option. In the case of vaccines forhuman influenza, approval of new strains is based largelyon an assessment that the analytical section of the dossierdemonstrates that the new antigen is of appropriate quality,together with some limited serology data. As a condition ofapproval, marketing authorisation holders enter intocommitments to provide confirmatory evidence of efficacyin the form of data from clinical trials conducted post-approval. A similar approach would be helpful on theveterinary side in order to rapidly approve new strains inthe event of epizootic situations.

ConclusionRecent experiences with FMD, BT and AI in the EU haveemphasised the need for national authorities to have accessto authorised vaccines to be used as part of the controlstrategy for these major epizootic diseases. Amendments tothe regulatory requirements would act as a significantincentive to manufacturers to authorise their vaccines. Thecurrent review of the technical requirements for obtainingand maintaining marketing authorisations within the EUpresents an ideal opportunity to introduce the concept ofthe ‘multistrain dossier’. This approach would more closelysuit the particular requirements of these antigenicallyvariable viruses and thereby promote the authorisation ofhigh quality vaccines.

AcknowledgementsThe author is grateful to Dr Nikolaus Kriz, EMEA, forreview of this manuscript.



L’agrément au sein de l’Union européenne

des vaccins dirigés contre des virus épizootiques majeurs

présentant une variabilité antigénique

D.K.J. Mackay

Résumé

Les virus présentant une variabilité antigénique sont à l’origine de maladies

parmi les plus contagieuses et les plus importantes du point de vue économique

qui affectent le bétail domestique. Les récentes épizooties de fièvre aphteuse et

les foyers d’influenza aviaire et de fièvre catarrhale du mouton survenus dans

l’Union européenne (UE) témoignent des pertes économiques que ces maladies

peuvent occasionner ainsi que de leurs conséquences néfastes pour la santé

humaine et animale. Face à ces maladies, les pouvoirs publics doivent être à

même d’apporter une réponse appropriée, notamment en recourant à des

vaccins adaptés à chaque situation épidémiologique. À l’heure actuelle, le cadre

réglementaire de l’UE ne permet pas d’autoriser ni de maintenir des vaccins

lorsque le choix de l’antigène doit se faire ultérieurement, en fonction des

nécessités épidémiologiques. L’ensemble des exigences techniques requises

pour l’autorisation de mise sur le marché des médicaments vétérinaires sont

actuellement en cours de révision au sein de l’UE. En outre, les réglementations

applicables à la mise à jour de ces autorisations sont également sur le point

d’être examinées. La possibilité est ainsi offerte d’introduire dans la législation

communautaire le concept de « demande d’autorisation multisouches »,

permettant aux autorisations de mise sur le marché de couvrir un nombre

potentiellement important de souches approuvées de sorte que le vaccin final

puisse être formulé en utilisant les souches nécessaires en fonction des

besoins. De plus, grâce à une procédure réglementaire simplifiée, de nouvelles

souches pourront être ajoutées aux autorisations de mise sur le marché si de

nouveaux variants antigéniques viennent à menacer l’UE.

Mots-clés

Autorisation – Autorisation de mise sur le marché – Fièvre aphteuse – Fièvre catarrhale

du mouton – Influenza aviaire – Union européenne – Vaccin.


Autorización de vacunas contra los virus con variaciones

antigénicas responsables de las principales enfermedades

epizoóticas en la Unión Europea

D.K.J. Mackay

Resumen

Algunas de las enfermedades más contagiosas y con mayores consecuencias

económicas que afectan a la ganadería de la Unión Europea (UE) pueden

imputarse a virus que presentan variaciones antigénicas. Las graves pérdidas

comerciales que ocasionan esas enfermedades, así como sus importantes

repercusiones en la salud humana y animal, quedaron demostradas tras las

epizootias de fiebre aftosa y los focos de influenza aviar y lengua azul que se

produjeron en los últimos tiempos. De ser preciso, las autoridades nacionales

han de poder enfrentarlas mediante medidas de inmunización adaptadas a la

situación epidemiológica. El marco reglamentario en vigor en la UE no es el más

conveniente para la aprobación y el mantenimiento de vacunas cuyos antígenos

deben poder seleccionarse en función del pronóstico epidemiológico. En la

actualidad se están examinando minuciosamente los requisitos técnicos para la

autorización de medicamentos de uso veterinario en la UE. Además, está por

iniciarse una profunda revisión de la reglamentación sobre la modificación de

los términos de esas autorizaciones. Se trata, pues, de una ocasión que

convendría aprovechar para introducir en la UE el concepto de “expedientes de

multicepas”, en virtud del cual se podría incluir un número potencialmente

elevado de cepas aprobadas en las autorizaciones de comercialización, y las

vacunas finales podrían combinarse de modo que comprendieran las cepas

correspondientes a las necesidades. Además, para prever la amenaza real o

potencial de nuevas variantes antigénicas en la UE, podría autorizarse la

introducción de nuevas cepas en esas autorizaciones mediante un mecanismo

reglamentario rápido.

Palabras clave

Autorización – Fiebre aftosa – Influenza aviar – Lengua azul – Registro – Unión Europea

– Vacuna.


References1. European Commission (2003). – Commission Regulation

(EC) No. 1084/2003 of 3 June 2003 concerning theexamination of variations to the terms of a marketingauthorisation for medicinal products for human use andveterinary medicinal products granted by a competentauthority of a Member State. Off. J. Eur. Union, L 159, 1-23.Available at: http://ec.europa. eu/enterprise/pharmaceuticals/eudralex/vol-1/reg_2003_ 1084/reg_2003_1084_en.pdf(accessed on 14 January 2007).

2. European Commission (2003). – Commission Regulation(EC) No. 1085/2003 of 3 June 2003 concerning theexamination of variations to the terms of a marketingauthorisation for medicinal products for human use andveterinary medicinal products falling within the scope ofCouncil Regulation (EEC) No. 2309/93. Off. J. Eur. Union, L 159, 24-45. Available at: http://ec.europa.eu/enterprise/pharmaceuticals/eudralex/vol-1/reg_2003_1085/reg_2003_1085_en.pdf (accessed on 14 January 2007).

3. European Medicines Agency (EMEA) (2004). – PositionPaper on Requirements for Vaccines against Foot-and-MouthDisease (adopted by the Committee for Medicinal Productsfor Veterinary Use [CVMP] June 2004). EMEA/CVMP/775/02. Available at: http://www.emea.europa.eu/pdfs/vet/press/pp/077502en.pdf (accessed on 14 January 2007).

4. European Medicines Agency (EMEA) (2004). – Guideline onRequirements for Vaccines for Use in Birds against AvianInfluenza. EMEA/CVMP/222624/06. Available at: http://www.emea.europa.eu/pdfs/vet/iwp/22262406en.pdf(accessed on 14 January 2007).

5. European Parliament (2001). – Consolidated Directive2001/82/EC of the European Parliament and of the Council of6 November 2001 on the Community code relating toveterinary medicinal products (Off. J. Eur. Communities, L 311, 1-66) as amended by Directive 2004/28/EC (Off. J. Eur. Union, L 136, 58-84). Available at:http://ec.europa.eu/enterprise/pharmaceuticals/eudralex/vol-5/consol_2004/veterinary_code.pdf (accessed on 14 January2007).

6. European Parliament (2004). – Regulation (EC) No.726/2004 of the European Parliament and of the Council of31 March 2004 laying down Community procedures for theauthorisation and supervision of medicinal products forhuman and veterinary use and establishing a EuropeanMedicines Agency. Off. J. Eur. Union, L 136, 1-33. Available at:http://ec.europa.eu/enterprise/pharmaceuticals/eudralex/ vol-1/reg_2004_726/reg_2004_726_en.pdf (accessed on 14 January 2007).


Regulations for vaccines against emerging

infections and agrobioterrorism

in the United States of America

L.A. Elsken (1), M.Y. Carr (1), T.S. Frana (1), D.A. Brake (2), T. Garland (2), K. Smith (2) & P.L. Foley (1)

(1) United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service, Veterinary

Services, Center for Veterinary Biologics, 510 S. 17th St., Ames, Iowa, 50010, United States of America

(2) United States Department of Homeland Security, Science and Technology Directorate, Washington, DC,

United States of America

Summary

The Virus-Serum-Toxin Act of 1913, as amended in 1985, provides the legal basis

for the regulation of veterinary vaccines and related biological products in the

United States of America (USA). The regulatory authority for the issuance of

licences and permits that allow the shipment or importation of pure, safe, potent,

and effective veterinary biological products lies with the Center for Veterinary

Biologics (CVB), an agency of the United States Department of Agriculture

(USDA). Under the standard licensing or permitting process, a manufacturer

must develop and completely characterise and evaluate a product prior to

licensure, and the CVB must review and evaluate the submitted information,

audit and inspect the manufacturing facilities and methods of production and

testing, and confirm key product test results through independent testing of

product. This complete and comprehensive evaluation may not be possible in

emergency situations, so processes and mechanisms are in place that allow for

the more rapid availability of veterinary vaccines. Next generation vaccine

development against foreign animal diseases such as foot and mouth disease is

actively in progress in the USA and the authorities must ensure that there is an

adequate supply of these vaccines in the National Veterinary Stockpile.

Keywords

Bioterrorism – Disease – Emergency – Emerging – Licensing – Regulatory – Vaccine –

Veterinary.

Introduction

Regulation of veterinary biological products in the UnitedStates of America (USA) began in 1913 with the passage ofthe Virus-Serum-Toxin Act by the United States Congress.The United States Department of Agriculture (USDA) isresponsible for regulating veterinary biological products,

including, but not limited to, vaccines, bacterins, toxoids,antibodies, and antitoxins which are intended for use inthe treatment of animals and which act primarily throughthe stimulation, supplementation, enhancement, ormodulation of the immune system or the immuneresponse. Because the term treatment, by definition,includes the prevention, diagnosis, management, or cure ofdiseases of animals, diagnostic test kits are also under

regulatory control by the USDA. The current USDAregulatory programme consists of:

– review of all data developed by manufacturers insupport of each product and product claim

– inspection of manufacturing processes and practicesincluding equipment, facilities, materials, personnel,production, quality control, and records

– confirmatory testing of manufacturers’ biological seeds,cells, and product

– a post-licensing monitoring system of inspection andrandom testing of product

– post-marketing epidemiological surveillance of productperformance under normal conditions of use.

This combination of regulatory oversight before and afterlicensure assures the availability of pure, safe, potent, andeffective veterinary biologics to veterinarians and animalowners. Under the standard licensing process, thisspectrum of evaluation and review includes the completecharacterisation, identification and purity testing of seedmaterials, product ingredients and the final product;environmental, laboratory, and host animal safety andefficacy studies; stability studies, and post-licensingmonitoring of field performance. All aspects of thiscomprehensive conventional evaluation may not bepossible during the emergence of a new animal diseaseagent or in an animal disease emergency such as in theintentional (agrobioterrorism) or unintentionalintroduction of a significant exotic animal disease agent. Inthese situations, the USDA has various mechanisms forexpedited product approval. In addition, the USDA mayalso provide exemption of products from some or all of theregulatory requirements for conventional productapproval. Implementation of these existing mechanismsand perhaps, the identification of other novel avenues forproduct approval will be critical for the acceleration andtimely development of next generation foreign animaldisease (FAD) vaccines and immune-basedbiotherapeutics.

Recently, to expedite emergency disease responsecapabilities, the Center for Veterinary Biologics (CVB), anagency of the USDA, has partnered with other authoritiesin the USA, such as the USDA’s National VeterinaryStockpile (NVS), and foreign regulatory authorities, suchas the Tripartite Canada-Mexico-USA North American Footand Mouth Disease Vaccine Bank, to purchase vaccineantigen concentrates and/or finished emergency usevaccines. In addition, the NVS is entering into contractualagreements with biologics manufacturers to ensureimmediate access to existing stocks of licensed emergency-use vaccines. These emergency preparedness products maybe licensed and distributed under standard processes or

with exemption from some or all of the normal regulatoryrequirements.

Regulatory frameworkThe Virus-Serum-Toxin Act of 1913 (Title 21 of the UnitedStates Code Parts 151-159) provides the legal basis for theregulation of veterinary biologicals in the USA; the CVBhas the regulatory authority for the issuance of licences andpermits for such products. The law was amended in 1985by the Food Security Act to include the distribution of allveterinary biologics (both interstate and intrastate) in theUSA as well as those intended for export. Administrativeregulations and standards appear in Title 9 of the Code ofFederal Regulations (9 CFR) Parts 101-118, withadditional programme guidance found in CVB Notices,Veterinary Services Memoranda, General LicensingConsiderations and other guidance documents. Veterinarybiologic products are defined in the regulations as ‘allviruses, serums, toxins (excluding substances that areselectively toxic to microorganisms, e.g. antibiotics), oranalogous products at any stage of production, shipment,distribution, or sale, which are intended for use in thetreatment of animals and which act primarily through thedirect stimulation, supplementation, enhancement, ormodulation of the immune system or immune response.’This includes, but is not limited to, vaccines, bacterins, allergens, antibodies, antitoxins, toxoids,immunostimulants, certain cytokines, antigenic orimmunising components of live organisms, and diagnosticcomponents that are of natural or synthetic origin or thatare derived from synthesising or altering various substances or components of substances such as microorganisms, genes or genetic sequences,carbohydrates, proteins, antigens, allergens, or antibodies.

The USDA is authorised to issue licences to veterinarybiologics manufacturers in the USA. In addition to whatare variously referred to as the ‘conventional’, ‘regular’ or‘full’ veterinary biological product licences in the USA,conditional biologics licences and autogenous biologicslicences may be issued for use in specific situations orunder certain conditions. Thus, some consideration shouldbe given to use these identified mechanisms for licenceapproval of next generation vaccines and immune-basedbiotherapeutics in order to reduce their overall time tooperational readiness.

The USDA is further authorised to issue three types ofpermits to allow the importation of veterinary biologics intothe USA. A Permit for Transit Shipment Only is requiredfor a biological product shipped from one non-US countryto another non-US country by way of the USA. A biologicalproduct issued a Permit for Transit Shipment Only may notbe used in the USA. A Permit for Research and Evaluation


may be issued if the manufacturer provides adequateinformation for the USDA to assess the product and theproduct’s impact on the environment and the productinvestigator (user) demonstrates scientific capabilitiesadequate to safeguard domestic animals (all animals, otherthan man, including poultry) and protect public health,interest, or safety from any deleterious effects which mightresult from the use of such product. For this permit type,the user could be the Department of Homeland Security(DHS) Science and Technology (S&T) Directorate ForeignAnimal Disease Biological Countermeasure Program atPlum Island Animal Disease Center (PIADC). Thisgovernment facility, located off the north-eastern tip ofNew York’s Long Island, is specifically designed to conductresearch and development studies on FADs and thus is ina unique position to further evaluate experimentalbiologicals that may be of value for further developmentand licensure. A Permit for Distribution and Sale may onlybe issued if the manufacturer and the permittee can insurethat the product is pure, safe, potent, and effective. APermit for Distribution and Sale is essentially equivalent toa conventional Veterinary Biological Product License in theUSA. For this permit type, DHS S&T could coordinateactivities between the foreign vaccine manufacturer andbiological company in the USA with a veterinaryestablishment licence.

The USDA’s Animal and Plant Health Inspection Service(APHIS) Administrator may also specifically exempt anyveterinary biological product from one or more of thenormal regulatory requirements under certaincircumstances, e.g. if the product is to be usedexperimentally (see section entitled ‘Exemption ofbiological products from licensing requirements’) or if thisproduct will be used by or under the supervision of theUSDA in the prevention, control, or eradication of animaldiseases in conjunction with:

a) an official USDA programme, or

b) an emergency animal disease situation, or

c) a USDA experimental use of the product.

DHS S&T can play an integral role in this exemptionpolicy by leading in the testing and evaluation ofexperimental vaccine product candidates for FADs. Thescientific data generated can be used, for example, to betterinform foot and mouth disease (FMD) modelling studies.In addition, DHS S&T can directly test or facilitate thetesting of FAD vaccines currently licensed andmanufactured in foreign countries. Examples includelicensed veterinary vaccines for FMD, highly pathogenicavian influenza, rinderpest, Rift Valley fever, and classicalswine fever. These current products can be characterised toyield new scientific data (e.g. days to onset of protection,virus shed/spread, vaccine dose sparing, etc.) that are

important in a decision process immediately followingoutbreak diagnosis.

All licences and permits issued by the CVB may includerestrictions on the distribution and use of the product (thisalso applies to products that have been exempted fromcertain other requirements by the APHIS Administrator).In an animal disease emergency such as in the intentional(bioterrorism) or unintentional introduction of asignificant exotic animal disease agent, these restrictionswould include, but not be limited to, the following:

– ‘Domestic distribution and use shall be under thesupervision or control of USDA, APHIS, VeterinaryServices, as part of an official USDA animal disease controlprogram.’

– ‘Distribution in each State shall be limited to authorizedrecipients designated by proper State officials––under suchadditional conditions as these authorities may require.’

DHS S&T can serve a coordinating role in obtainingscientific data that can be used by APHIS-VeterinaryServices to help underpin decisions on the specificrestrictions under which these exempted products wouldbe used. Examples include data on the ability of testmaterial to reduce pathogen shed (including the durationof reduction) and the ability of the product to be used in aDifferentiating Infected from Vaccinated Animals (DIVA)diagnostic recovery phase programme.

The CVB’s Inspection and Compliance (CVB-IC) section isresponsible for determining whether licensed andpermitted companies are being properly inspected andwhether the products they manufacture are beingprepared, tested, and distributed according to allapplicable regulations and requirements. Major CVB-ICactivities include on-site inspections of manufacturing andquarantine facilities, control and release of product batches(serials), and post-licensing product monitoring(pharmacovigilance). Licensed and permittedmanufacturing establishments are subject tocomprehensive in-depth inspections at one to three yearintervals. In-depth inspections include 14 categories ofinspection, each of which includes numerous itemssuggesting records to audit and items for observation. Thecategories of inspection considered in all in-depthinspections include licences, personnel, facilities,equipment, sanitation, research, seeds and cells,production, final production, labels, testing, animals,distribution, and miscellaneous (includingpharmacovigilance). Special inspections of establishmentsare also utilised to address issues such as:

– observation of pivotal pre-licence efficacy or safetystudies

– auditing of production, quality control, or animal test records


– inspection of new facilities or equipment

– review of product distribution or pharmacovigilancerecords.

Each licensee or permittee is required to furnish the CVBwith representative samples of every vaccine master seedorganism and master cell stock proposed for use in thepreparation of veterinary biological products, and samplesof each serial or subserial of finished veterinary biologicalproduct manufactured in or imported into the USA. TheAPHIS Administrator is authorised to cause these samplesto be examined and tested for purity, safety, potency, andefficacy. A master seed organism or master cell stock foundunsatisfactory by any test may not be used to prepareveterinary biological products. A serial or subserial foundto be unsatisfactory by a required test prescribed in anapproved Outline of Production or Standard Requirementis not in compliance with the regulations, and may not bereleased for distribution.

Data and review requirementsfor conventional productlicences or permits for distribution and saleAll regulations pertaining to product licences or permitsfor distribution and sale (data requirements, confirmatorytesting by the CVB, inspection and compliancerequirements – see following sections) are contained in 9CFR Parts 101-118. Pre-licensing data evaluation andreview procedures are designed to assess the purity, safety,potency, and effectiveness of each product and support allproduct label claims. In order to fulfil these criteria, datafrom all phases of product development are evaluatedagainst these key elements. This spectrum of evaluationincludes complete characterisation and identification ofseed material and ingredients, laboratory and host animalsafety and efficacy studies, demonstration of stability, andmonitoring of field performance. Specific purity, safety,potency, and efficacy requirements are described in thefollowing paragraphs.

Purity

All product components and ingredients must meetstandards of purity and quality. Master seed, master cellstock, primary cells, ingredients of animal origin, and finalproducts must be tested and shown to be free ofextraneous microorganisms. This requirement is especiallyimportant in a scenario in which veterinary vaccineslicensed and produced overseas would be considered for

use in an animal disease emergency. DHS S&T PIADC canprovide a proactive, coordinating role in the testing ofmaster seed, cell stocks, and formulated vaccines for thepresence of foreign animal disease agents. Eggs used inproduction of biological products must be acquired fromspecific-pathogen-free flocks. Purity and identification ofmaster seed and master cell are confirmed by testing at theCVB. In addition to the first serials (batches of completedproduct) prepared under licence, a random sample ofserials are subjected to pre-release purity testing at the CVBto verify manufacturer’s quality assurance/quality controlon final product.

Safety

Products must be shown to be safe through a combinationof safety evaluations. Master seeds and master cell stocksmust be fully identified and characterised. Productionpassage levels (limits) are established for both seeds andcells. Master seeds for live products are tested for shed,spread, and reversion to virulence through backpassagestudies in the host animal. Following a minimum of fivepassages in the host, recovered isolates are fullycharacterised using the same procedures used for themaster seed. Demonstration of an acceptable level ofattenuation must be shown. Other safety studies arerequired as appropriate (e.g. safe use in pregnant animals,environmental safety, safety of adjuvants in products forfood-producing animals). Field safety studies designed todetect unexpected reactions that may not have beendetected in product development are required beforelicensure. The CVB and DHS S&T must decide if the nextgeneration FAD vaccines currently under development willbe exempt from this requirement or if field safety vaccinetrials in foreign countries with reported FAD will berequired. Host animal tests are conducted at a variety ofgeographical sites using large numbers of susceptibleanimals representing all ages and husbandry practices forwhich the product is intended. Final product serials are subjected to safety testing primarily through in vivoanimal tests.

Efficacy and potency

All products must be shown to be effective according to theclaims indicated on the label, and each batch (serial) ofeach product must demonstrate potency at least equal tothat of the reference serial(s). As defined by regulations inthe USA, efficacy is a product characteristic, demonstratedat least once prior to licensure, while potency is a batchmeasure, and is intended to confirm that a serial will be atleast as effective as a known immunogenic serial. The twoterms can be distinguished as follows:

– efficacy is the specific ability or capacity of a biologicalproduct to effect the result for which it is produced, when


used under the conditions recommended by themanufacturer

– potency is the relative strength of a biological product asdefined by test methods or procedures established byAPHIS in the 9 CFR Standard Requirements or in theapproved Outline of Production for the product.

Efficacy is generally demonstrated by statistically valid hostanimal vaccination-challenge studies and must becorrelated to the product potency assay. The followinggeneral considerations are applied to efficacy studies:

– immunogenicity studies must be conducted usingminimum levels of antigen at the highest passage levelfrom the master seed that is permitted for production;

– product must be prepared in production facilities on ascale representative of normal production;

– challenge methods and criteria for evaluating protectionwill vary with the immunising agent, but in general, testsare conducted under controlled conditions usingseronegative animals of the youngest age recommended onthe label;

– duration of immunity data is required for some existingproducts (e.g. for rabies) and for all newly licensedantigens;

– field efficacy studies may be considered wherelaboratory animal challenge models are not wellestablished. Similarly, serologic data may be used toestablish efficacy only when serology is indicative ofprotection;

– data is required for each species for which the productis recommended and for each route, dose, and regimen ofadministration;

– for products with two or more fractions (components),data demonstrating no antigenic interference is required;

– stability studies are required to set the expiration dateon the label;

– potency tests correlated to host animal vaccination anddesigned to measure the relative strength of each serialmust be developed prior to full licensure. In addition, eachserial must be formulated and tested prior to marketing toensure effectiveness and reproducibility of activity(potency) according to standards set at the time oflicensing. Generally, this is accomplished through anestablished immune-mediated animal or in vitro assay or byusing microbiological counts or virus titrations for livebacterial or viral products.

Risk analysis

The CVB uses risk analysis procedures to evaluate licenceapplications for all ‘new’ live conventionally-derived

vaccines and biotechnology-derived veterinary biologics,and to assess proposals to import veterinary biologics intothe USA. To facilitate the preparation of scientifically validand credible risk analyses, the CVB has developedSummary Information Formats (SIFs) and Risk Assessment(RA) outlines to provide guidance to interested parties. TheSIFs and RA outlines identify the relevant information thatshould be evaluated in veterinary biologics risk analysis,and may be downloaded from the CVB website.

The SIF for conventionally-derived live vaccines isdesigned to identify the appropriate information thatshould be provided to properly characterise the vaccinemicroorganism, based on its microbiological and biologicalproperties, and those of the parental microorganism fromwhich the vaccine strain was derived.

The SIF for Category I biotechnology-derived veterinarybiologics is designed to identify the appropriateinformation that should be provided to properlycharacterise the recombinant microorganisms forinactivated biotechnology-derived veterinary biologics.Subcategories for inactivated biotechnology-derivedveterinary biologics are as follows:

– I-A-1, bacterins, killed virus vaccines, and subunitvaccines

– I-A-2, recombinant antigens for use in diagnostic testkits

– I-B-1, monoclonal antibodies for therapeutic orprophylactic use

– I-B-2, monoclonal antibodies for use in diagnostic testkits

– I-C-1, synthetic peptides for therapeutic or prophylacticuse

– I-C-2, synthetic peptides for use in diagnostic test kits

– I-D-1, nucleic acid-mediated vaccines

– I-D-2, nucleic acid-mediated diagnostic test kits.

Inactivated biotechnology-derived microorganisms can beused in the manufacture of ‘killed’ vaccines, subunitvaccines, and diagnostic kits. The characterisation of theinactivated microorganism centres on its molecularproperties, as well as on those of the parentalmicroorganism and on any deleted or donor genes.Obviously, it is not anticipated that inactivatedmicroorganisms will pose a threat to the environment.Accordingly, for inactivated biotechnology-derivedproducts, the veterinary biologics risk analysis process isused to ensure that the biotechnology-derivedmicroorganism is properly characterised and inactivated.Risk analyses to evaluate proposed environmental releasesof inactivated products are not conducted.


The SIF for Category II biotechnology-derived veterinarybiologics is designed to identify information needed toproperly characterise microorganisms for biotechnology-derived live vaccines containing gene deletions and\orheterologous marker genes. The characterisation of thegene-deleted microorganism includes the molecular andbiological properties of the vaccine microorganism, and ofthe parental microorganism receiving the geneticmodifications.

The SIF for Category III biotechnology-derived veterinarybiologics is designed to identify information needed toproperly characterise the vaccine microorganisms forbiotechnology-derived live vector vaccines containingheterologous genes encoding immunising antigens and\orother immune stimulants. The characterisation ofbiotechnology-derived vector vaccines includes themolecular and biological properties of the recipient, thedonor, and the recombinant master seed microorganism.The characterisation of the donor microorganism includesthe properties of both the donated structural genes andtheir regulatory elements. It is anticipated that the majorityof next generation molecular vaccines and/or immune-based biotherapeutics for FADs currently underdevelopment by DHS S&T will fall under this riskclassification.

A risk analysis prepared by the licensee or permittee mustbe submitted to the CVB for pre-licence evaluation of everyCategory I, II, or III biotechnology-derived product. Therisk analysis should contain the most current version of theSIF and a risk assessment based on safety characteristics ofthe vaccine. A risk assessment outline for use in thepreparation of risk analyses for biotechnology-derivedproducts is available from the CVB.

Risk analyses for environmental release must be preparedby licensees or permittees for new live conventionallyderived and biotechnology-derived veterinary vaccines.The risk analysis needs to include environmental releaseassessments, which evaluate the safety characteristics ofthe vaccine microorganism within the context of the targetenvironment. A SIF which identifies the information thatshould be included in release assessments for proposedenvironmental releases is available from the CVB. Prior tothe first release of a live biotechnology-derived veterinaryvaccine determined not to have a significant impact on thequality of the human environment, the CVB prepares anenvironmental assessment and advises the public of plansfor field testing the vaccine. The CVB also provides publicnotice of their intent to issue a product licence or permitfor the vaccine, provided the field test data support theconclusions of the environmental assessment and theissuance of a finding of no significant impact and theproduct meets all other requirements for licensing.

The veterinary biologics risk analysis model for importingveterinary biologics centres on the risk of introducing

FADs into the USA through the importation of acontaminated veterinary biological product. This requires athorough evaluation of all potential sources ofcontamination during the development and manufactureof the product. The SIF for importation of veterinarybiological products identifies the information regarding thefacilities, reagents, production procedures, and testingprocedures that should be evaluated when preparing riskanalyses for proposals to import veterinary biologicalproducts into the USA. As previously discussed, DHS S&TPIADC can play an important coordinating role ingenerating additional, scientific data that can be used in therisk analysis model, such as BSL3 Ag (biosafety level 3 foragricultural hazards) safety testing in animals of veterinarybiologics that may be candidates for importation.

Licensing data should be developed and submitted forlicensure in a logical sequence representing successivesteps in product development (e.g. master seed purity andidentity, laboratory safety, immunogenicity, initialproduction serials [usually three], purity, safety, potencytesting, and field safety). All data generated in productdevelopment is required to be reported to the CVB.

Confirmatory testing by theCenter for Veterinary Biologicslaboratory for conventionalproduct licences or permits for distribution and saleThe laboratory staff within the CVB conduct assays onveterinary biological products and key biologicsmanufacturing materials (master seed bacteria, master seedvirus, and master cell stocks) as required in 9 CFR parts101-118. Primary activities include:

– pre-licence testing

– test development and standardisation (including reagentactivities)

– post-licence quality control monitoring.

Pre-licence testing by the CVB laboratory for conventionalproduct licences or Permits for Distribution and Saleincludes assaying both parent materials (master seeds andcells) and final product. Master seeds and master cellstocks are evaluated for purity and identity (includingidentity of construct and expressed antigen for geneticallyengineered products). Prior to licensure or permitting of aproduct, a manufacturer is required to demonstrate theirability to consistently produce pure, safe, and potentproduct. This is usually accomplished through the


satisfactory production of three consecutive, independentpre-licence serials. Before a licence or permit is issued, thepurity, safety, and potency of pre-licence serials will beconfirmed by testing in the CVB laboratory. This testingassures that the product tests are appropriate andtransferable and that the manufacturer is able toconsistently reproduce quality product.

It is important to note that although all tested master seeds,master cells, and pre-licence serials have been tested by themanufacturer and submitted to the CVB as satisfactory, theCVB laboratory regularly finds a small percentage of seeds,cells, and products that are not pure, safe, potent, oreffective.

Inspection and compliance requirements for conventionalproduct licences or permits for distribution and saleAccording to Title 9 of the CFR, parts 101-118, for a USmanufacturer to distribute veterinary biological products,the producer must hold valid licences of two types:

– a United States Veterinary Biologics EstablishmentLicense

– one or more Veterinary Biological Product Licenses.

In order to distribute veterinary biological productsmanufactured outside the USA, a permittee (defined as anyindividual, firm, partnership, corporation, company,association, educational institution, state or localgovernment who resides in the USA or operates a businessestablishment within the USA) must hold a United StatesVeterinary Biologics Establishment License and a UnitedStates Veterinary Biological Product Permit, ForDistribution and Sale. Thus, the distribution of FADimported vaccines that may be of interest to the NationalVeterinary Stockpile will require the identification of acompany, individual or government authority that iswilling to apply for these licences and to serve as thepermittee. Partnerships between DHS S&T and privateindustry will most likely be required to ensure programmesuccess, since the customer target for these importedproducts will be USDA APHIS and the National VeterinaryStockpile, rather than traditional meat, milk and eggproducers.

Prior to the issuance of an establishment licence or permitfor distribution and sale, an applicant for biologicsmanufacturing must address the following items:

a) the regulations require that manufacturingestablishments be operated under the direct supervision ofpersons competent by education and experience to handleall matters pertaining to the preparation and testing ofbiological products. Summaries of the relevantqualifications for each supervisory employee responsiblefor essential steps in production, testing, and initialdistribution of products must be provided to and acceptedby the CVB;

b) facility documents, including plot plans for allbuildings, blueprints for each building used in preparingbiological products, and blueprint legends which provide abrief description of all activities in each room or area of aproduction facility must be submitted to and accepted bythe CVB;

c) for each room, the blueprint legend should include:

– all activities conducted in a room, for example,inoculation, harvest, concentration, filling, etc.

– all microorganisms prepared, tested, or stored in theroom, including an indication of whether themicroorganism is viable or killed

– a listing of stationary or other essential equipment suchas mills, centrifuges, mixing tanks, bottling and sealingequipment, etc.

– for rooms where products are exposed to thesurroundings, a description of decontaminationprocedures and other precautions against cross-contamination;

d) the regulations require buildings to be constructed sothat:

– the floors, walls, ceilings, partitions, posts, doors, andall other parts of all structures, rooms, or facilities used inthe preparation of biologicals can be readily andthoroughly cleaned

– all rooms are located and arranged to prevent cross-contamination of products

– there are adequate air handling systems to ensuresanitary and hygienic conditions for the protection ofproducts and personnel

– there are separate rooms or compartments forpreparing, handling, or storing virulent or dangerousmicroorganisms

– adequate hot and cold water supplies and efficientdraining and plumbing systems are provided for animalsand equipment;

e) equipment cleaning, pasteurisation, sterilisation,temperature recording devices or other records ofsterilisation must be acceptable;

f) all animals used in the preparation or testing ofbiologicals must be healthy. Animals admitted into, usedin, and disposed of from biologics production areas must


meet the standards in the regulations for biologics and theAnimal Welfare Act;

g) records and record-keeping systems must be adequateto give a complete accounting of all activities within eachestablishment, including all procedures used in all steps inthe preparation, testing, and disposition of products;

h) if, at any time, there are indications that raise questionsregarding the purity, safety, potency, or efficacy of aproduct, or if it appears that there may be a problemregarding the preparation, testing, or distribution of aproduct released for marketing, the manufacturer mustagree to immediately notify the CVB concerning thecircumstances and the action taken;

i) written assurance must be filed with the CVB that thelicensed or permitted products will not be advertised so asto mislead or deceive the purchaser and that the packagesor containers used in marketing the product will not bearany statement, design, or device which is false ormisleading in any particular;

j) for biologics manufacturers in the USA, the entirepremises of an establishment are subject to inspection, atany time, without prior notification. The regulationsspecifically authorise inspection of ‘all buildings,compartments, and other places, all biological products,and organisms and vectors in the establishment’, and allmaterials and equipment, such as chemicals, instruments,apparatus, and the like, and the methods used in themanufacture of, and all records maintained relative to,biological products produced at such establishments;

k) for non-US manufacturing facilities, the producer andpermittee must agree to submit to periodic inspections ofthe production facilities, and the permittee must agree tobe responsible for all costs associated with the inspections.

Before a United States Veterinary Biologics EstablishmentLicense or a United States Veterinary Biological ProductPermit, For Distribution and Sale is issued, a pre-licenceinspection by the CVB must confirm whether thecondition, equipment, facilities, methods, etc. used toprepare biological products conform with the above itemsand all other requirements in the US regulations.

Expedited processes forveterinary biologics in theUnited States of AmericaIdeally, a fully licensed or permitted vaccine is available foruse in the USA to aid in the control of a new or emerginganimal disease or when vaccine is immediately required to

aid in a response to an intentional (bioterrorism) orunintentional introduction of a significant animal diseaseagent not normally found in the USA. If not, the processesand mechanisms described in this section have been usedin the USA to allow for the more rapid availability ofveterinary vaccines in an emerging or emergency animalhealth situation.

Conditional product licences

Conditional licences (regulated by 9 CFR Part 102.6) areauthorised under very specialised circumstances to meetan emergency condition, limited market, local situation, orother special circumstance. Licences are issued under anexpedited procedure which assures purity and safety, andprovides a reasonable expectation of efficacy and/or potencyfor the vaccines involved. The data generated by amanufacturer to provide this reasonable expectation varies,and is evaluated on a case-by-case basis, but licences havebeen issued in the following situations:

a) efficacy data was adequate, but correlation to theproposed potency assay was not determined or validated

b) clinical or experimental efficacy studies suggested aprotective effect against disease, but did not providedefinitive data

c) a scientifically accepted correlate of efficacy, such as avirus, toxin or similar neutralising antibody titre or levelwas available.

It is important to note that approvals allowing thepreparation of vaccines under conditional licences aretime-limited, and manufacturers must actively pursue datato support full licensure. It is also important to note thatthe CVB may not issue ‘Conditional Permits.’ Conditionallicences may only be issued to biologics manufacturers inthe USA.

Vaccine prepared under a conditional licence must be incompliance with all other applicable licensing regulationsand standards. This will involve, for example, conductingpre-licence field safety studies, following data and riskanalysis procedures, advising the public prior to release oflive biotechnology-derived vaccines, obtaining satisfactoryresults from confirmatory testing of seeds, cells, and pre-licence serials by the CVB laboratory, and complying withfacility and other CVB inspection requirements.

Use of conditional licences for new FAD vaccines shouldbe contemplated in strategic countermeasure programmesin which funds for full licensing may be limited and/or thespecific advanced price or purchase commitments by theNational Veterinary Stockpile are not well established. Thiswill ultimately translate to biologics manufacturingcapacity incentives.


Autogenous product licences or permits for distribution and sale

Regulations concerning autogenous product licences andpermits are contained in 9 CFR Part 113.113. Autogenousbiologics are prepared from cultures of microorganismswhich have been inactivated and are non-toxic. Suchproducts are to be used only by or under the direction of aveterinarian within a veterinarian-client-patientrelationship. The microorganisms used as seed to prepareautogenous biologics must be isolated from sick or deadanimals in the herd of origin and there must be reason tobelieve they are the causative agent(s) of the currentdisease affecting such animals. Autogenous isolates maynot be modified by biotechnology methods. Normally,microorganisms from one herd are not to be used toprepare an autogenous biologic for another herd. However,under certain circumstances, preparation of an autogenousbiologic for use in herds other than the herd of origin,when those herds are considered to be at risk and have anepidemiologic link, may be authorised. In general, themicroorganism(s) used for the production of autogenousbiologics must be used within 15 months of the date ofisolation, or within 12 months of the date of harvest of thefirst serial of product produced from the microorganism(s),whichever comes first. Testing requirements forautogenous products include testing of final containersamples for purity (sterility) and mouse and/or guinea pigand/or host animal safety tests. Master seed testing by themanufacturer is not required, nor is any CVB laboratoryconfirmatory testing of the seeds or cells conducted.Products must include a label precaution that potency andefficacy have not been established. A licence to produce,distribute or ship autogenous products includes therestriction that the licence does not authorise production,distribution, or shipment of autogenous vaccine/bacterinfor the following:

– foot and mouth disease

– rinderpest

– any H5 or H7 subtype of avian influenza

– any subtype of avian influenza if the vaccine is intendedfor use in chickens

– swine vesicular disease

– Newcastle disease

– African swine fever

– classical swine fever

– Brucella abortus

– vesicular stomatitis

– rabbit haemorrhagic disease

– any other disease that the USDA determines may pose arisk to animal or public health.

Autogenous FAD vaccines are not an attractive option for acountermeasure programme due to the high risk involvedin manufacturing the live pathogen prior to inactivationand the increased investment that would be required to build separate, dedicated manufacturing facilities toproduce these vaccines.

Vaccine prepared under an autogenous licence or permitmust be in compliance with all other applicable licensingregulations and standards, including risk analysisprocedures. Manufacturer’s purity and safety test resultsmay be confirmed by testing in the CVB laboratory. Allmanufacturing establishments are thoroughly inspected(personnel, facilities, production processes, record-keeping) as CVB compliance requirements must be met.

Experimental product approvals

Regulations pertaining to experimental product approvalsare contained in 9 CFR Parts 103.3 and 104.4. Under veryspecific circumstances the experimental production,distribution, and evaluation of biological products bymanufacturers in the USA may be authorised prior to fulllicensing or permitting. For the benefit of licenceapplicants and to permit and encourage research, a personmay be authorised to ship unlicensed biological productsfor the purpose of evaluating such experimental productsby treating limited numbers of animals. Conditions mustexist to ensure the experiment is conducted in a manner toprevent the spread of disease, with special restrictionsimposed in the case of products containing live organisms.Requests for authorisation to ship an unlicensed biologicalproduct for experimental study and evaluation shall be accompanied by certain information including thefollowing:

– a permit or letter of permission from the animal healthauthorities of each US state or foreign country involved;

– a tentative list of the names of the proposed recipientsand quantity of experimental product that is to be shippedto each individual;

– a description of the product, recommendations for use,and results of preliminary research work;

– labels or label sketches which show the name oridentification of the product and bear a statement, ‘Notice!For Experimental Use Only – Not For Sale’, or equivalent.The US Veterinary License legend shall not appear on suchlabels;

– a general plan covering the methods and procedures forevaluating the product and for maintaining records of thequantities of experimental product prepared, shipped andused;

– data demonstrating that use of the experimentalbiological product in meat animals is not likely to result in


the presence of any unwholesome condition in the edibleparts of animals subsequently presented for slaughter;

– a statement from the research investigator or researchsponsor agreeing to furnish, upon the Administrator’srequest, additional information concerning each group ofmeat animals involved prior to their movement from thepremises where the test is to be conducted. Suchinformation must include the owner’s name and address;number, species, class and location of animals involved;date the shipment is anticipated; name and address ofconsignee, buyer, commission firm or abattoir;

– information in order to assess the product’s impact onthe environment.

Permits are not issued for biological products fromcountries known to have exotic diseases – including, butnot limited to, FMD, rinderpest, highly pathogenic avianinfluenza, swine vesicular disease, Newcastle disease, andAfrican swine fever – if such products may endangerlivestock or poultry in the USA.

Recently, DHS S&T has partnered with the CVB andindustry to secure permission for the shipment ofexperimental FMD vaccine candidates to PIADC forefficacy studies in livestock. Continuation of thispartnership will be important to allow for the timelyidentification of lead candidates for further development.

Exemption of biological products from licensing requirements

The APHIS Administrator may exempt any veterinarybiological product from any or all of the licensing orpermitting requirements (9 CFR Part 106.1) if the productswill be used by the USDA, or under the control andsupervision of the USDA, for the prevention, control, oreradication of animal disease in any of the followingcircumstances:

a) as part of an official USDA programme

b) in an emergency animal disease situation

c) as part of a USDA experimental trial.

DHS S&T can provide value-added information fordecisions regarding product exemption by conductingscientific studies designed specifically to characterise theproduct in the context of its effectiveness as an emergency-use countermeasure tool.

Homeland Security Presidential Directive 9 and the National Veterinary Stockpile

The economic and social impacts of an outbreak of ahighly contagious animal disease in the USA, such as FMD,

would be dramatic. In the event of such an outbreak, thelost export markets for live animals and meat products andthe multiplier effect of lost production would be feltthroughout the US economy.

On 30 January 2004, Homeland Security PresidentialDirective 9 (HSPD-9) established a national policy todefend the agriculture and food system in the USA againstterrorist attacks, major disasters, and other emergencies.This directive noted that this would be done by:

– identifying and prioritising sector-critical infrastructureand key resources for establishing protection requirements

– developing awareness and early warning capabilities torecognise threats

– mitigating vulnerabilities at critical production andprocessing nodes

– enhancing screening procedures for domestic andimported products

– enhancing response and recovery procedures.

As a part of response planning and recovery, HSPD-9directed the creation of a National Veterinary Stockpile(NVS) containing sufficient amounts of animal vaccine,antiviral, diagnostic, or therapeutic products toappropriately respond to the most damaging animaldiseases affecting human health and the economy. TheNVS is mandated to be capable of deployment within 24hours of an outbreak. The ability to respond to theintentional, simultaneous introduction of disease agents inmultiple locations (i.e. an act of terrorism) is a particularfocus for the NVS.

The NVS is the national repository of vaccines, personalprotective equipment, and other critical veterinaryproducts. It exists to augment state and local resources inthe fight against dangerous animal diseases that couldpotentially devastate American agriculture, seriously affectthe economy, and threaten public health.

The NVS reflects two significant changes in the way APHISis able to respond to and eradicate animal diseases, asfollows:

a) previously, functional groups of specialists respondingto an outbreak managed their own logistics support. Thisfragmentation has caused several problems:

– groups duplicate the efforts of others

– planning before an event is more complex andpotentially incomplete

– coordination of resources during an event is moredifficult when products come from multiple sourcesmanaged by multiple groups


– costs of responding are higher because each grouppurchases supplies in smaller quantities and at high prices

b) in the past, APHIS eradicated disease outbreaksprimarily by destroying infected and potentially exposedanimals. However, given both changes in agriculturalpractices in the USA (e.g. herd sizes are much larger thanin the past), and the availability of animal disease controlmodels and scenarios involving multifocal diseaseoutbreaks, planning disease control options beyondquarantine and depopulation is prudent. Vaccine in theNVS gives APHIS another option.

Within five years, the NVS intends to acquire vaccine,diagnostic testing capabilities, and therapeuticcountermeasures against a variety of the most significantanimal diseases, including highly pathogenic avianinfluenza, FMD, Rift Valley fever, exotic Newcastle disease,and classical swine fever. Within ten years, NVS plans toacquire countermeasures against all of the most dangerousdiseases of animals. In order to rapidly deliver largequantities of critical veterinary supplies and equipment tothe right place, at the right time, for as long as is necessary,the NVS is:

– directly obtaining, stockpiling and managing finishedvaccines and other ready-to-use supplies for delivery bythe NVS within 24 hours

– contracting, for delivery within 24 hours, for stocks ofvendor-managed vaccines, diagnostic tests and reagents,and other perishable supplies

– developing both government and vendor-managedbiologics precursors suitable for long-term storage andrapid formulation into needed products (e.g. vaccineantigen concentrates for highly pathogenic avian influenzaand FMD).

Veterinary biologics acquired by or contracted to the NVSmay be any licensed, permitted, experimental, orexempted product, as is deemed prudent by risk analysis.

DHS S&T can function as the single point of authority foreither leading or coordinating the development ofveterinary biodefence countermeasures for procurement

by the NVS. DHS S&T can provide a permanent fundingsource through which the federal government can co-develop next generation vaccines or novel immune-basedbiotherapeutics with private industry. Industrydevelopment costs can be off-set and minimised byforming strategic partnerships with DHS S&T. Thisapproach is currently being used to establish a pipeline ofnext generation molecular vaccines for FMD. Expansion ofthis approach for other high priority foreign disease agentsof threat to agriculture will be critical to enable the NVS toreach its five-year and ten-year objectives.

ConclusionThe procedures reviewed above provide a regulatoryframework and outline general purity, safety, potency, andefficacy requirements for licensing of products fortraditional animal diseases, emerging animal diseases, andthe accidental or intentional introduction of animaldiseases. Supplementary procedures may be required forcertain products. These regulatory processes demonstratethe flexibility of the current regulatory system toaccommodate a variety of animal health situations whileproviding the data-driven, performance-based oversightnecessary to assure that only quality biologicals areavailable for use. DHS S&T, USDA-CVB and othergovernment agencies of the USA must work together in acoordinated fashion to ensure the successful developmentand availability of highly efficacious, biological-basedcountermeasures for the US National Veterinary Stockpile.



Réglementation applicable aux vaccins contre

les maladies infectieuses émergentes et à l’agro-bioterrorisme

aux États-Unis d’Amérique

L.A. Elsken, M.Y. Carr, T.S. Frana, D.A. Brake, T. Garland, K. Smith & P.L. Foley

Résumé

Aux États-Unis d’Amérique, la loi de 1913 sur les virus, les sérums et les toxines

(Virus-Serum-Toxin Act) telle qu’amendée en 1985, constitue le fondement

juridique de la réglementation relative aux vaccins vétérinaires et aux produits

biologiques à usage vétérinaire. L’autorité réglementaire chargée de délivrer les

autorisations de mise sur le marché et les autorisations d’expédition ou

d’importation de médicaments vétérinaires purs, sans danger, puissants et

efficaces est une agence sous tutelle du Département américain de

l’Agriculture, le Center for Veterinary Biologics (CVB). Conformément à la

procédure normalisée d’autorisation, les fabricants doivent développer,

caractériser intégralement et évaluer les produits candidats avant de présenter

une demande d’autorisation ; ces informations sont ensuite examinées et

évaluées par le CVB, puis celui-ci procède à un audit et à une inspection des

établissements du fabricant et de ses méthodes de production et de test ; les

principaux résultats des tests relatifs au produit sont ensuite vérifiés lors d’un

examen indépendant. Cette évaluation exhaustive n’étant pas toujours possible

dans les situations d’urgence, des procédures et des mécanismes particuliers

sont prévus afin que des vaccins vétérinaires soient rapidement disponibles

dans ces situations. Des vaccins de nouvelle génération contre des maladies

animales exotiques telles que la fièvre aphteuse sont en cours de

développement aux États-Unis, et il appartient aux autorités compétentes de

s’assurer que la réserve nationale de vaccins vétérinaires en contienne un stock

suffisant.

Mots-clés

Autorisation de mise sur le marché – Bioterrorisme – Maladie – Maladie émergente –

Réglementation – Urgence sanitaire – Vaccin – Vaccin vétérinaire.

References1. Bunn T.O. (1992). – Testing of veterinary biologics in the

United States. Dev. biol. Standard., 79, 187-192.

2. Espeseth D.A. (1995). – Present systems and future needs forrisk assessment of biologicals in the United States of America:the perspective of the regulator. In Risk assessment forveterinary biologicals (E.G.S Osborne & J.W. Glosser, eds).Rev. sci. tech. Off. int. Epiz., 14 (4), 1143-1155.

3. Espeseth D.A. & Myers T.J. (1999). – Authorities andprocedures for licensing veterinary biological products in theUnited States. Adv. vet. Med., 41, 585-593.

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6. Hill R.E., Foley P.L., Carr M.Y., Elsken L.A., Gatewood D.M.,Ludemann L.R. & Wilbur L.A. (2003). – Regulatoryconsiderations for emergency use of non-USDA licensedvaccines in the United States. Dev. Biol. (Basel), 114, 31-52.

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8. United States Code of Federal Regulations (2006). – Title 9 –Animals and Animal Products.


Reglamentación sobre vacunas contra infecciones

emergentes y bioterrorismo en los Estados Unidos de América

L.A. Elsken, M.Y. Carr, T.S. Frana, D.A. Brake, T. Garland, K. Smith & P.L. Foley

Resumen

En los Estados Unidos de América (EE.UU.), la ley relativa a los virus, sueros y

toxinas (Virus-Serum-Toxin Act) de 1913, modificada en 1985, constituye la base

legal de la reglamentación sobre las vacunas de uso veterinario y los productos

biológicos conexos. El Centro de Productos Biológicos de Uso Veterinario (CVB,

Center for Veterinary Biologics), un organismo del Departamento de Agricultura

de ese país, es el ente regulador de la concesión de autorizaciones de

exportación e importación de productos biológicos de uso veterinario puros,

inocuos, potentes y eficaces. De conformidad con el procedimiento normalizado

de otorgamiento de licencias y permisos, es preciso que los fabricantes hayan

desarrollado, caracterizado y evaluado totalmente un producto antes de que se

le otorgue la homologación. A su vez, el CVB ha de revisar y evaluar la

información presentada, examinar los métodos de producción y prueba, realizar

una inspección de las plantas de elaboración, y someter los resultados de los

ensayos de los productos clave a un organismo independiente para su

verificación. En situaciones de emergencia puede carecerse de tiempo

suficiente para efectuar esa evaluación global y exhaustiva; por consiguiente se

han establecido procedimientos y mecanismos para disponer de vacunas de uso

veterinario con mayor rapidez. El desarrollo de la nueva generación de vacunas

contra enfermedades animales foráneas, como la fiebre aftosa, avanza con

rapidez en los EE.UU. Las autoridades deben asegurarse de que se suministren

cantidades suficientes de esas vacunas a la Reserva Nacional Veterinaria.

Palabras clave

Autorización de comercialización – Bioterrorismo – Emergencia – Emergente –

Enfermedad – Regulación – Vacuna – Veterinaria.


L’expérimentation animale dans la découverte

et la production de vaccins à usage vétérinaire

J.-Ch. Audonnet (1), J. Lechenet (2) & B. Verschuere (3)

(1) Département de recherche exploratoire, Mérial, 254, rue Marcel-Mérieux, 69007 Lyon, France

(2) Département des affaires réglementaires Europe, enregistrements biologiques, Mérial,

29, avenue Tony-Garnier, 69007 Lyon, France

(3) Groupe interprofessionnel de réflexion et de communication sur la recherche (GIRCOR), 15 rue Rieux,

92100 Boulogne, France

Résumé

Les établissements de recherche, de développement et de production des

vaccins vétérinaires doivent répondre aux questions du public, aux exigences de

la réglementation et aux objectifs d’amélioration de la bientraitance animale,

tout en assurant leur mission de production de vaccins toujours plus efficaces et

plus inoffensifs. Le recours à l’animal pour la mise au point et le développement

de nouveaux vaccins vétérinaires est inévitable, aucun modèle in vitro ne

permettant de prédire la capacité d’un candidat vaccin à induire une protection

chez l’espèce cible. Face aux contraintes éthiques et réglementaires, les

progrès pour la mise en œuvre des meilleures conditions possibles pour

l’utilisation des animaux d’expérience sont permanents. L’évolution constante

dans le domaine de l’éthique animale impose un effort particulier à l’industrie

pharmaceutique qui doit modifier avec rigueur les documents à l’appui de

l’enregistrement en fonction de chaque nouveau développement.

Mots clés

Développement – Embryon – Expérimentation animale – Modèle in vivo – Recherche –

Vaccin à usage vétérinaire.

IntroductionDepuis plusieurs années, l ’ expérimentation animale est unthème de débat social. Partagée entre les arguments deschercheurs qui expliquent et prouvent régulièrement lanécessité du recours à l ’ animal pour le progrès scientifiqueet médical, et la compassion pour les animaux qui seronttués et qui souffriront peut-être de ces expériences,l ’opinion publique ne peut donner une réponse simple à laquestion : « êtes-vous pour ou contre l ’ expérimentationanimale ? ». Selon le contexte dans lequel la question estposée, la réponse pourra être « je suis pour, mais il faudraitque les animaux ne souffrent pas, ou souffrent le moinspossible » ou « je suis contre, sauf si cela doit sauver desvies humaines ou d’autres vies animales plusnombreuses ».Les sondages d’opinion réalisés régulièrement sur ce thèmerévèlent invariablement que la position du public estconditionnée par le « pourquoi ? » et le « comment ? ».

Selon la raison pour laquelle on a recours àl ’ expérimentation animale (le « pourquoi ? »), cetteexpérimentation sera plus ou moins acceptée. Dans cedomaine, la santé humaine et la santé animale sont lesraisons qui entraînent clairement la plus forte adhésion dupublic. Les conditions dans lesquelles l ’ expérimentationanimale est réalisée (le « comment ? »), sont aussi unélément clé sur lequel s’appuiera la perception (positive ounégative) du public : le respect de la condition animale autravers du respect absolu de la réglementation et desnormes professionnelles, la formation des chercheurs, laqualité des installations d’animaleries, les comitésd’éthique et la présence de vétérinaires, sont des élémentsclés de l’appréciation.

Face à ces interrogations de la société, le législateur alogiquement mis en place un système de textes quiencadrent l ’ expérimentation animale conformément auxvœux des citoyens. On voit dans tous les pays occidentaux

des réglementations de plus en plus convergentes quidemandent que l’expérimentation animale répondeobligatoirement à des nécessités de recherche, de contrôle,de sécurité du consommateur ou d’enseignement, qu’ellesoit réalisée uniquement dans des établissementsréférencés et contrôlés par une autorité désignée, et enfinque des comités d’éthique examinent et apprécient defaçon indépendante le bien-fondé de la recherche et lesconditions de sa réalisation. Des centres nationaux ouinternationaux subventionnés par des fonds publics ou privés ont été créés dans le but de promouvoir oudévelopper des méthodes scientifiques qui permettentd’utiliser moins d’animaux ou en induisant moins dedouleur, de stress ou d’inconfort, le cas échéant. Cescentres (par exemple le European Centre for the Validationof Alternative Methods [ECVAM] : http://ecvam.jrc.it/ enItalie ; le Interagency Coordinating Committee on theValidation of Alternative Methods [ICCVAM] : http://iccvam.niehs.nih.gov/ aux États-Unis d’Amérique ; leEuropean Consensus-Platform for Alternatives [ECOPA] :http://www.ecopa.eu/ en Belgique ; et le National Centrefor the Replacement, Refinement and Reduction ofAnimals in Research [NC3R] : http://www.nc3rs.org.uk/ auRoyaume-Uni) visent à appliquer au plus près duchercheur et de l’animal de laboratoire la règle dite des« trois R » (remplacement, réduction, raffinement) promuedès 1959 par Russell et Burch (7). Très tôt, l ’ industrie duvaccin vétérinaire a pris en compte les exigencesréglementaires et éthiques liées à l ’utilisation des animauxen recherche et développement (R&D).

L’objet de cet article est de présenter comment lesétablissements de recherche, de développement et deproduction des vaccins vétérinaires répondent auxquestions du public, aux exigences de la réglementation etaux objectifs de la règle des trois R tout en assurant leurmission qui est de protéger toujours plus efficacement lesanimaux contre les maladies à l ’ aide de vaccins les plusinoffensifs possibles.

Historique de l’expérimentationanimale pour les vaccins et cadre réglementaireLes animaux domestiques ont été associés audéveloppement des vaccins dès l’origine du concept mêmede vaccin. En effet, c’est la production en grande quantité,par scarification de flancs de génisses, du virus de la« vaccine » de Jenner que la « vaccination » a purapidement diffuser d’abord en Europe puis dans le mondeentier. Mais ce sont ensuite Pasteur et ses disciples (dont denombreux vétérinaires) qui ont réalisé les premièresexpérimentations animales raisonnées à des fins derecherche et de développement de vaccins. Le vaccin de la

rage (à destination de l ’homme) a été ainsi précédé par lamise au point de plusieurs vaccins vétérinaires (charbon,choléra de la poule…) qui ont confirmé la possibilitéd’induire une protection solide contre les maladiesinfectieuses par l ’ immunisation avec des « vaccins ». Si lesprincipes généraux des contrôles de qualité n’étaient biensûr pas encore connus au XIXe siècle, il n’est pas moinsédifiant de savoir que la rigueur scientifique de Pasteurl’avait déjà poussé à contrôler les « lots » de vaccin contrela rage avant de les utiliser chez l ’homme en toute sécurité.

La Directive européenne 2001/82/EC (amendée le 31 mars2004) (4) définit les produits immunologiques commesuit : « un médicament vétérinaire administré aux animauxen vue de provoquer une immunité active ou passive ou dediagnostiquer l ’ état d’immunité ». L’ immunité active(vaccins classiques) induit des états de protection plus oumoins complets qui sont détaillés dans les indicationsreconnues officiellement par les autorités d’enregistrement.

De nos jours, des vaccins vétérinaires existent pour toutesles espèces et permettent de combattre toutes les grandesmaladies. Ce sont des outils essentiels pour le maintien de l ’ état sanitaire de nos élevages et pour le bien-être desanimaux de rente et de compagnie.

Particularités de la recherche et du développement pour les vaccins vétérinairesSi les outils qui aident à la sélection des vaccins vétérinaireset à leur production montrent une convergence inéluctableen technicité et en qualité avec les vaccins humains, ungrand « avantage » pour les vaccins vétérinaires est queleur évaluation se réalise sur l ’ espèce cible (bénéficiairedirecte du vaccin développé). Mais l’« art » de cetteévaluation reste complexe, particulièrement dans ledomaine vétérinaire où les équipes de R&D sontconfrontées à de nombreuses espèces différentes et à desindividus non standardisés quant aux niveaux de réponseimmunitaire et aux spécificités de cette réponse. La plupartdes maladies étant strictement spécifiques d’espèce, il estmalheureusement impossible d’extrapoler facilement à uneautre espèce les résultats obtenus sur une espèce donnée.Les travaux de R&D pour les vaccins vétérinairesrequièrent un très grand savoir-faire dans la maîtrise desmodèles animaux (sur espèces cibles) qui n’est en généralobtenu qu’après de longues années de pratique et unecapacité à déduire des conclusions solides d’un ensemblede données caractérisées par une grande variabilité.

Le corollaire de l’utilisation importante des espèces ciblespour la R&D des vaccins vétérinaires est que ces animaux,


bien que considérés comme des animauxd’expérimentation animale ne sont pas forcément perçuspar le public comme des animaux d’expérience ou desanimaux de laboratoire. Les carnivores (chiens, chats,furets, etc.) exceptés, les animaux de rente (bovins, ovins,caprins, porcs, poulets, dindes, oies, canards, etc.) ou leschevaux sont en effet rarement assimilés spontanément parle public à des « animaux de laboratoire ».

Utilisation des animauxd’expérimentation au cours des étapes du développementdes vaccins vétérinairesLa phase « pré-clinique », classique dans ledéveloppement des vaccins humains, n’existe pas pour lesvaccins vétérinaires.

Ceci est dû à plusieurs raisons :

– des animaux de l ’ espèce cible (dits « d’expérience »)peuvent être utilisés directement, et très en amont, dansdes études d’innocuité et d’efficacité ;

– les résultats obtenus n’en sont que plus pertinents pourle vaccin étudié ;

– c’est une contrainte réglementaire imposant dereproduire la maladie chez les animaux en expérience pourdémontrer visiblement la protection attendue et de réaliserla démonstration de toutes les qualités du nouveau vaccindans un environnement maîtrisé (étude en laboratoire ;partie C des 7e et 8e parties de l’Annexe 1 de la Directiveeuropéenne 2001/82/CE) (4) ;

– enfin, le temps de développement est raccourci.

L’un des bénéfices, inconnus du grand public, du recoursdirect à l’espèce cible est que cette démarche, trèspragmatique et habituelle pour le monde vétérinaire, évitel’utilisation des nombreux rongeurs qui sonttraditionnellement associés aux phases pré-cliniques desvaccins humains.

Une autre particularité est le fait que les vaccinsvétérinaires qui s’adressent aux animaux de production(bovins, ovins, porcs, poulets, dindes, etc.) sont desvaccins « économiques ». Ce facteur pousse à uneoptimisation (en nombre de protocoles et en nombred’animaux par protocole) des coûts de R&D et limite doncles recours inutiles. La conjonction de ces particularités faitque le processus de R&D pour les vaccins vétérinaires tendfortement à s’autolimiter pour ce qui concerne le nombred’études et le nombre des animaux engagés dans ces

études, compte tenu de tailles des marchés beaucoup pluspetites que pour les vaccins humains. La genèse d’unvaccin vétérinaire s’organise autour de plusieurs phasessuccessives : recherche, développement, enregistrement,commercialisation et suivi post-lancement.

Première phase : recherche

La faculté de pouvoir intervenir chez l’espèce cible dès ledébut de la phase de recherche est une « chance » pour lavaccinologie vétérinaire car elle permet d’avoir desréponses rapides quant à la « faisabilité » du candidatvaccin. Mais c’est à condition de disposer d’un modèled’épreuve fiable et reproductible. C’est dans cette étape demise au point du modèle infectieux que l’on utilise le plusd’animaux, car de nombreuses variables sont malmaîtrisées au départ. Toutefois le nombre total d’animauxutilisés à ce stade reste limité. Les contraintes éthiques,économiques et pratiques (lorsque l’on travaille parexemple avec de grandes espèces comme le cheval) sontimportantes et contribuent, outre les encadrementsréglementaires et éthiques, à optimiser au mieux ladémarche expérimentale. Dans ces étapes, les nombresminima d’animaux par groupe sont validés par les bio-statisticiens en fonction de la variabilité connue du modèle,de manière à garantir que les résultats seront interprétables(et donc d’éviter de faire des expériences inutiles aux plansscientifique et éthique).

Pour l’espèce cible, on utilise en moyenne 100 à 200 animaux, selon qu’il est nécessaire ou non de mettreau point le modèle d’épreuve (dans le cas d’une nouvellemaladie) et que la pathologie infectieuse à laquelle ons’adresse est simple ou non. En effet, si la reproductionexpérimentale de la maladie est bien maîtrisée, quelquesétudes seulement permettront un tri très pertinent etefficace des différentes options qui existent lors de la phase« recherche ». Dans le cas contraire, la définition d’unmodèle suffisamment reproductible pour donner desinformations fiables peut être longue et consommatriced’animaux.

Au cours de la phase « recherche », un nombre assez limitéde rongeurs et lapins (quelques dizaines au plus) peutservir également à la préparation de réactifs sérologiquesspécifiques aux antigènes du vaccin étudié.

Deuxième phase : développement et enregistrement

Comme pour la phase précédente, cette phase vaconcerner essentiellement les animaux de l’espèce cibleafin de vérifier les caractéristiques intrinsèques du vaccin etde générer les données cliniques du dossierd’enregistrement. Au total, moins d’une centaine


d’animaux sont impliqués en général pour un dossierconcernant un vaccin pour un mammifère, mais les vaccinspour volailles peuvent nécessiter de plus grands nombres,plus pour des raisons historiques ou de pharmacopée quepar réelle nécessité scientifique ou technique.

Une exception notable est le cas des vaccins recombinésvivants (« vaccins à vecteur ») pour lesquels il faut en plusévaluer l ’ innocuité dans d’autres espèces (vérification de l’absence de modification du tropisme et de l’absencede virulence) afin d’étudier son comportement dans desenvironnements variables. Cette phase est très encadréepar les exigences réglementaires : Directives européennes90/219/CE (utilisation en milieu confiné) (2) et2001/18/CE (dissémination dans l’environnement, c’est-à-dire hors confinement) (3).

Le développement est aussi le moment où différents testsde contrôle doivent être mis au point pour que le fabricantpuisse suivre et garantir la régularité et la qualité des lotsde vaccins lors des opérations de production commerciale.Les « tests d’activité » sont traditionnellement réalisés sur des petits rongeurs de laboratoire et l ’ établissementd’une corrélation solide entre la réponse sérologique des rongeurs et celle de l ’ espèce destinataire n’est parfoispas évident. C’est souvent cette mise au point qui entraîneles plus grandes consommations d’animaux (jusqu’àplusieurs centaines voire quelques milliers dans des casextrêmes) (6).

Les animaux utilisés lors de l’essai terrain

Les essais cliniques sur le terrain ont pour but de vérifieren « conditions réelles » l ’ innocuité du vaccin sur ungrand nombre d’individus « tout venant ». Le but et laconception de l ’ essai terrain pour les vaccins vétérinairesdiffèrent clairement de la phase III des essais cliniquespour les vaccins humains qui ont pour but de démontrerl ’ efficacité statistique du vaccin. Nous avons vu plus hautque l’efficacité du vaccin vétérinaire est démontrée très tôtpar épreuve expérimentale sur l’espèce cible, dès la phasede recherche, puis confirmée lors de la phase dedéveloppement. À ce stade, les essais n’ont donc pour butque de confirmer les résultats à grande échelle. Le principalpoint à retenir ici est que les essais terrain sont soumis àautorisation réglementaire et que les animaux engagés dansces essais le sont après consentement de leurs propriétaireset n’ont donc pas le statut d’animaux d’expérimentation.

Troisième phase : mise sur le marché(production et vente, tests de contrôle qualité)

Il faut distinguer dans ce paragraphe l ’ utilisation des animaux comme support direct pour la production desvaccins (exemples désormais rarissimes) de l ’utilisation des animaux pour les contrôles réglementaires de qualitédes vaccins commerciaux.

Production in vivo (sur animaux ou embryons)

De nos jours très peu de vaccins utilisent des animauxpour leur production. Sont préférés de très loin pour desraisons de reproductibilité industrielle, de bio-sécurité et de coût, les productions sur cellules de lignée. Les lapinset certaines volailles sont les seuls animaux encore utiliséspour de très rares produits. La raison est souvent l ’ absenced’un système in vitro de culture de l ’ agent pathogène,l ’ animal étant malheureusement le seul support possible.

L’utilisation d’embryons de poulets (sous forme d’œufsembryonnés) est par contre beaucoup plus fréquente,l’œuf étant un système industriel très répandu pour laproduction de certains vaccins (l ’ exemple le plus connu etle plus important en volume est celui du vaccin de la grippe humaine). Nous sommes ici à la frontière entre ce qu’il est convenu de considérer comme un « animal »ou pas. De nombreux comités d’éthique établissentd’ailleurs des limites précises (âge d’incubation) pour lafrontière entre l ’ embryon de poulet « non animal » et« animal » (5).

Production in vitro (sur cellules primaires,

cellules de lignée, milieux de culture pour bactéries)

Cette production in vitro ne met pas en œuvre l ’utilisationd’animaux.

Libération des lots et mise en circulation des vaccins

Si les opérations de production proprement diten’impliquent quasiment plus l ’ usage d’animaux, des« techniques de contrôle » sur animaux (principalementdes rongeurs) sont obligatoires afin de pouvoir « libérer »les lots de vaccins conformément aux exigencesréglementaires du dossier d’autorisation de mise sur lemarché (AMM). Ces contrôles sont :

– des tests d’innocuité spécifique (sur espèce cible) et nonspécifique (sur petits rongeurs) ; ces derniers tests ontdisparu des obligations réglementaires alors que lespremiers tendent à disparaître. En effet, aprèsdémonstration d’une bonne innocuité sur un certainnombre de lots différents de production, et si le procédé de fabrication est jugé robuste, il est possible de s’affranchirde ce test (5) ;

– des « test d’activité » dans le cas des vaccins inactivésseulement (test généralement fait sur rongeurs) : unnombre limité d’animaux est utilisé pour chaque lot(généralement une dizaine), mais le nombre total estfonction du nombre de lots de vaccins à tester. Il fautsouligner que la mise en œuvre généralisée des normes debonnes pratiques de fabrication a fortement contribué à ladiminution du nombre d’animaux nécessaires au contrôledes vaccins via différents facteurs. Par exemple,


l ’ augmentation de la taille des lots industriels, suite à lafiabilisation des procédés, a un impact direct très concretsur le nombre d’animaux utilisés.

Quatrième phase : soutien du produit

L’histoire d’un vaccin ne s’arrête pas à l ’ enregistrement etil est parfois important pour le producteur de générer desdonnées complémentaires au dossier (mais non nécessairesà l ’ enregistrement pharmaceutique) qui sont utiles poursoutenir les ventes du vaccin et pour renforcer sa positionconcurrentielle.

Ces essais complémentaires vont concerner bien sûr lesanimaux de l ’ espèce cible et engager quelques dizainesd’animaux au maximum. Selon les cas, les essais serontfaits soit en station expérimentale (animaleries de R&D,donc animaux d’expérimentation), soit sur le terrain, aprèsautorisation administrative, avec des animaux de statutnormal (on ne parlera alors pas d’animauxd’expérimentation).

Il peut être précisé que parfois l ’ environnementréglementaire évolue et les conclusions scientifiques sontune nouvelle fois questionnées par les autorités, non pasparce qu’elles ne sont plus fondées, mais parce que leprotocole de l ’ étude n’est plus conforme aux dernièresexigences, obligeant ainsi de refaire cette étude voire unepartie du développement (Directive européennen° 2001/82/CE, article 27) (4).

Progrès dans le domaine réglementaireL’utilisation des animaux, même pour des raisons de contrôle de qualité de production se doit de répondreaux attentes du public. Les textes de base (Directiveeuropéenne 86/609/CE) (1) ont aidé les autorités à accepter une moindre utilisation et l ’élimination de duplications inutiles. La mise en place de ces textes a également favorisé la modification des esprits qui aconduit à des cadres réglementaires encourageant cettediminution. Par exemple la Pharmacopée européenne (6),dans sa partie introductive sur le vaccin (Monographie n° 62) mentionne :

« Essais sur animaux. Conformément aux dispositions dela Convention européenne sur la protection des animauxvertébrés utilisés à des fins expérimentales et à d’autres finsscientifiques, les essais doivent être réalisés de telle façonqu’ils utilisent le moins d’animaux possible et qu’ilsréduisent au minimum toute douleur, souffrance, détresseou nuisance durable ».

Cette tendance à la diminution des animaux pour lescontrôles de qualité a surtout été rendue possible du fait del’introduction des bonnes pratiques de fabrication (BPF) etd’un nombre grandissant d’outils sophistiqués pour lecontrôle de la qualité du vaccin. De très nombreuxparamètres sont désormais suivis et « mis sous contrôle »,permettant de mieux garantir la reproductibilité d’un lot àl ’ autre. Les améliorations de procédé sont mises en placeaprès validation complète et après autorisation desautorités d’enregistrement. La qualité de production estplus prédictible, la qualité se construit durant laproduction, ce qui réduit ainsi les besoins de contrôle.C’est un des facteurs importants ayant permis la disparitiondu test de toxicité anormale demandé par la Pharmacopéeeuropéenne, qui était très consommateur de cobayes etsouris. Un suivi plus rapproché du médicament après lavente a été également instauré : la pharmacovigilance. Toutproblème vu lors de l’utilisation du vaccin sur le terrainpeut être rapporté aux autorités et aux laboratoiresproducteurs. Aujourd’hui, les conclusions sur lesobservations du terrain confirment que les manquesd’efficacité ou les réels problèmes d’innocuité sont peunombreux (validant ainsi la qualité du développement surespèce cible même avec un faible nombre d’animaux). De même une bonne innocuité en général des vaccins estconfirmée. Ce nouvel outil a donné plus confiance àl ’ ensemble des acteurs pour qu’en association avec la miseen place des BPF, une réduction des tests (donc desanimaux utilisés) soit entreprise.

L’utilisation très directe de l’espèce cible pour la recherche etle développement des vaccins vétérinaires est accueillieplutôt favorablement par le public quand il est averti, car lesrésultats pertinents générés par cette démarche contribuentà limiter très fortement le nombre d'animaux utilisés.

ConclusionLe recours à l ’ animal d’expérimentation pour la mise aupoint et le développement de nouveaux vaccinsvétérinaires est malheureusement inévitable. Aucunmodèle théorique ou in vitro ne permet en effet de prédireou décrire la capacité d’un candidat vaccin à induire uneprotection chez l ’ espèce cible. Par ailleurs, le vaccin est unmédicament, produit fortement réglementé pour assurerun niveau de qualité irréprochable. Face à ces contrainteséthiques et réglementaires, les chercheurs ont développédes stratégies pour limiter au maximum le nombred’animaux utilisés. Les vétérinaires et les chercheurs del ’ industrie au contact des animaux sont très conscients quela mise en œuvre de conditions visant à un bien-êtreoptimal des animaux en expérimentation est un facteuressentiel de qualité pour les études. Tous ces personnelssont engagés dans une démarche permanente de progrèspour améliorer sans cesse les conditionsd’expérimentation.



Les progrès pour la mise en œuvre des meilleuresconditions possibles dans l ’ utilisation des animauxd’expérimentation sont permanents et constants dans ledomaine de la R&D des vaccins vétérinaires. Ces progrèscorrespondent aux principes des trois R, déclinés espècepar espèce et modèle infectieux par modèle infectieux.

La perception du public vis-à-vis de l ’ expérimentationanimale change au cours du temps, de même que celle desexpérimentateurs, car ceux-ci font aussi partie du

« public ». La prise en compte d’une évolution constantedans le domaine de l’éthique animale demande un effortparticulier dans l ’ environnement pharmaceutique du faitde la rigueur à observer pour la documentation deschangements dans les documents de référence. Cet effortest toutefois légitime et il est directement récompensé parla fierté de réaliser des améliorations au bénéfice del ’animal.

La experimentación con animales en relación con el

descubrimiento y la producción de vacunas de uso veterinario

J.-Ch. Audonnet, J. Lechenet & B. Verschuere

Resumen

Los establecimientos de investigación, desarrollo y producción de vacunas

veterinarias deben responder a las demandas del gran público, a los requisitos

reglamentarios y a los objetivos de mejora del bienestar de los animales, y al

mismo tiempo cumplir su función de elaborar vacunas cada vez más eficaces e

Animal experimentation in the

discovery and production of veterinary vaccines

J.-Ch. Audonnet, J. Lechenet & B. Verschuere

Summary

Veterinary vaccine research, development and production facilities must aim to

improve animal welfare, respond to public concerns and meet regulatory

requirements, while at the same time fulfilling their objective of producing ever-

more effective and safer vaccines. The use of animal experimentation for the

development of new veterinary vaccines is inevitable, as no in vitro model can

predict a candidate vaccine’s ability to induce protection in the target species.

Against the backdrop of ethical and regulatory constraints, constant progress is

being made in creating the best possible conditions for animal experimentation.

Keeping up to date with the constant changes in the field of animal ethics

requires a particular effort on the part of the pharmaceutical industry, which

must make careful changes to product registration documentation in

accordance with each new development.

Keywords

Animal experimentation – Development – Embryo – In vivo model – Research –

Veterinary vaccine.

Bibliographie1. Communautés européennes (1986). – Council Directive

86/609/EEC of 24 November 1986 on the approximation oflaws, regulations and administrative provisions of theMember States regarding the protection of animals used forexperimental and other scientific purposes. Off. J. EuropeanCommunities, L 358, 18/12/1986, 1-28 (page web: http://europa.eu.int/eur-lex/lex/LexUriServ/Lex UriServ. do?uri=CELEX:31986L0609:EN:HTML, consultée le 30 mai 2007).

2. Communautés européennes (1990). – Directive 90/219/CEEdu Conseil, du 23 avril 1990, relative à l ’utilisation confinéede micro-organismes génétiquement modifiés. J. off. Unioneur., L 117, 08/05/1990, 0001-0014 (page web : http://eur-lex. europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31990L0219:FR:HTML, consultée le 30 mai 2007).

3. Communautés européennes (2001). – Directive 2001/18/CEdu Parlement Européen et du Conseil du 12 mars 2001relative à la dissémination volontaire d’organismesgénétiquement modifiés dans l’environnement et abrogeantla directive 90/220/CEE du Conseil. J. off. Communautés eur., L 106/1, 17/4/2001, 1-38 (page web : europa.eu.int/eur-lex/pri/fr/oj/dat/2001/l_106/l_10620010417fr00010038.pdf,consultée le 30 mai 2007).

4. Communautés européennes (2001). – Directive 2001/82/CEdu Parlement européen et du Conseil du 6 novembre 2001instituant un code communautaire relatif aux médicamentsvétérinaires [amendée par la Directive 2004/28/CE duParlement européen et du Conseil du 31 mars 2004

modifiant la directive 2001/82/CE instituant un codecommunautaire relatif aux médicaments vétérinaires (Texteprésentant de l ’ intérêt pour l ’EEE)]. J. off. Union eur., L 311,28/11/2001, 1-6 (pages Web : http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32001L0082:FR:HTML ; directive amendée : http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32004L0028:FR:HTML,consultées le 30 mai 2007).

5. Institutional Animal Care and Use Committee (2005). –Policy on the use of avian embryos. Page web : http://casemed.case.edu/ora/iacuc/policies/avian_embryos.cfm(consultée le 30 mai 2007).

6. Pharmacopée européenne (2005). – Vaccins pour usagevétérinaire. Monographie n° 62. Pharmacopée européenne.Site web : http://online.pheur.org/entry.htm (consultée le 30 mai 2007).

7. Russell W.M.S. & Burch R.L. (1959). – The principles ofhumane experimental technique. Methuen & Co., Londres.


inocuas. El recurso a los animales para poner a punto y desarrollar vacunas es

inevitable, pues ningún modelo in vitro permite predecir la capacidad de una

eventual vacuna para inducir protección en la especie destinataria. Ante las

exigencias de orden ético y reglamentario, constantemente se vienen

mejorando las condiciones en que se utilizan animales con fines

de experimentación. El continuo progreso de la ética en este campo exige un

particular esfuerzo por parte del sector farmacéutico, que debe observar

un gran rigor para modificar los documentos de referencia utilizados para el

registro de las vacunas en función de cada nuevo desarrollo.

Palabras clave

Desarrollo – Embrión – Experimentación con animales – Investigación – Modelo in vivo

– Vacuna de uso veterinario.


Consumer attitudes to vaccination of food-producing animals

J.M. Scudamore

University of Liverpool, Faculty of Veterinary Science, Leahurst, Neston, South Wirral, CH64 7TE, UnitedKingdom

SummaryThe 2001 outbreak of foot and mouth disease in the United Kingdom wasunprecedented, with the need to develop a vaccination policy at the height of theepidemic. The extent of consumer concerns about eating products derived fromvaccinated animals was unknown as survey results were equivocal. A recentsurvey on avian influenza reveals that the European public are well informedabout the disease and its control, but over 50% of respondents would bereluctant to consume meat from vaccinated birds. There is little specificinformation available on consumer views about routine vaccination for otherdiseases. Their concerns appear to increase in an emergency situation whenthere is heightened awareness through the media. With the development ofnewer types of vaccines consumers will need more assurance about the safetyand use of these products. This article examines these issues and makespractical recommendations for ensuring public confidence when emergencyvaccination for disease control is proposed.

KeywordsAvian influenza – Consumer attitudes – Consumer concern – Food safety – Foot andmouth disease – Lessons learned – Public confidence – Vaccination.

IntroductionIt is difficult to obtain detailed information on consumerattitudes to eating products from food-producing animalswhich have been vaccinated, especially as there is limitedinformation in the literature. A compounding problem isthat consumers often only consider the issue when there isheightened media interest and emergency vaccination is tobe used in the face of an outbreak of an epizootic diseasesuch as foot and mouth disease (FMD) or avian influenza(AI). The FMD outbreak in the United Kingdom (UK) in2001 and the current situation with respect to AI alongwith a number of recent surveys provide some indicationof consumer attitudes.

Foot and mouth disease vaccination

The 2001 outbreakThe UK outbreak of FMD began in February 2001. Thefinal case occurred on 30 September 2001, just over sevenmonths after the commencement of the outbreak. The lastremaining FMD-infected area was pronounced clear on the4 December 2001. In January 2002, the WorldOrganisation for Animal Health (OIE) declared the UK freeof FMD without vaccination. The UK approach prior tothe FMD outbreak in 2001 was to rely on a traditional

stamping out policy. Field instructions for vaccination wereavailable prior to the outbreak but only as an outlineprocedure which had not been publicised or discussedwith stakeholders.

Vaccination was considered during the first weeks of theoutbreak but was thought to be impractical due to thewidespread dissemination of infection throughout thecountry. Vaccination was subsequently consideredthroughout the epidemic and on at least ten specificoccasions. Apart from a proposal to vaccinate cattle inCumbria and Devon (which was accepted but ultimatelynot carried out – see next paragraph) vaccination was ruledout for a number of reasons. It was recognised that theeradication of FMD in most areas could be achievedquickly and most effectively with minimal disruptionthrough culling and tighter biosecurity.

The vaccination of cattle in Cumbria and possibly Devonwas under active consideration from the end of March.These were areas where the concentration of disease andthe local farm structure made it difficult to control thedisease without large-scale slaughter of exposed animals.The proposed vaccination was intended to protect cattlewhich were due to move out of the winter housing ontospring pasture. The potential loss of particularly largenumbers of animals and the difficulties in disposing ofcarcasses made vaccination an important option in thesetwo areas.

The government accepted the case for an emergencyvaccination programme and on 28 March 2001, the UKobtained authority (Decision 2001/257/EC) from theEuropean Commission in Brussels to apply emergencyvaccination in Cumbria and Devon. It was clear, however,that any vaccination programme could only succeed withsubstantial support from the key stakeholders, includingfarmers, veterinarians, consumers, retailers and foodmanufacturers. By the end of April it was evident that thelevel of support for vaccination was insufficient and withthe reducing number of cases in Cumbria and Devon thejustification for vaccination was less compelling.

Stakeholder concernsStakeholders were consulted throughout the discussionson vaccination but attempting to obtain their support atthe height of the epidemic was difficult. Food safety wasnot considered to be a specific issue but it was recognisedthat vaccination could result in problems if consumerperceptions about the safety of milk and meat changedafter vaccination was introduced. If consumer fears aboutvaccination gained any credence some sections of the foodindustry considered that this could lead to a two-tiermarket in meat and dairy products.

The food industry was concerned over the sale of producefrom vaccinated animals, particularly the marketing of theproduce post vaccination. The overall message from thefood retailers was that they would expect to continuestocking meat and milk from pooled milk supplies whichincluded product from vaccinated herds provided publicconfidence remained.

Retailers provided assurances about the marketing ofproducts from vaccinated animals but indicated theywould need to reconsider their position if consumerresistance was encountered. The key consideration forretailers was public confidence. If that were to disappearand customers were to demand that product be labelled toidentify whether it was from vaccinated or unvaccinatedanimals the retailers would need to respond. In thesecircumstances retailers might decide to source their milkand meat only from unvaccinated herds. Many consideredthese fears to be exaggerated but possible consumerreactions in the midst of an outbreak are difficult to predictso there could be no certainty about the results.

Food safety issues Early in the outbreak the UK Food Standards Agency (FSA)issued guidance on the safety of eating meat and milk fromanimals vaccinated against FMD. This guidance referred tothe UK Veterinary Products Committee (VPC) safetyassessments of the O1 Manisa vaccine (available from theInternational Vaccine Bank), which already had a UKmarketing authorisation at the time of the outbreak.

A commercially available FMD vaccine was purchasedduring the outbreak as a precautionary measure in theevent that large-scale vaccination was required at a laterstage. This vaccine had been assessed by the VPC for safety,quality and efficacy and had received a UK marketingauthorisation from the Veterinary Medicines Directorate(VMD). Unfortunately, due to time constraints the finalpotency testing required under the terms of the licencewere not conducted in the early stages of the outbreak. Ifthe vaccine had been used in the earlier stages of theepidemic it would have been released as an unauthorisedmedicine. Legally it would not have been the same productas that holding the marketing authorisation and it couldnot have been labelled with the same trade name. In theevent, potency testing was completed later in the year anda full marketing authorisation was issued.

In the case of an unauthorised product, assurances wouldneed to be sought from the manufacturer that themanufacturing process was the same as for the authorisedproduct and that for all practical purposes theunauthorised product would be the same as the authorisedproduct. Provided appropriate assurances were receivedfrom the manufacturer the use of the vaccine would poseno problems.


Vaccination against other diseases

Avian influenzaThe UK has recently ordered 10 million doses of AI vaccinefor potential use in poultry and other captive birds. Thevaccines could be used against both the H5 and H7 strains.These vaccines have a provisional marketing authorisationfrom the VMD which confirms their safety and quality.Purchasing these vaccines is a precautionary measure takenas part of the contingency plan that has been established inthe light of the uncertainties which exist about the futurespread and nature of the virus. Vaccination would only beused if risk assessment and scientific evidence indicatedthat it would help to prevent the spread of disease.Stakeholders have agreed that preventative vaccination ofpoultry is not the most effective defence against AI becausecurrently available vaccines have a number ofdisadvantages.

The European Medicines Agency has recentlyrecommended that three AI vaccines should be givenmarketing authorisations under exceptional circumstances.This provides for an accelerated assessment because withthe current concerns about the AI situation in both birdsand humans there is an urgent need for authorisedvaccines to be available as part of disease controlcampaigns. Their use entails specific obligations (whichwill be reviewed annually) that are intended to provideadditional assurance in relation to the products and toensure a programme of active pharmacovigilance shouldthe vaccines be used in the field. These vaccines will onlybe used as part of disease control programmes incompliance with European Union (EU) legislation.Authorisation of these products will provide assurances tonational authorities of the quality of the vaccines.

Other diseasesThere are increasing threats from other diseases, many ofwhich pose a risk to humans as well as animals. From apublic health perspective AI poses a major risk, but withclimate change and globalisation other potential zoonosessuch as Rift Valley fever may also constitute a threat toEurope. Foot and mouth disease, classical swine fever(CSF), African swine fever, and swine vesicular disease, allhave the potential to create economic problems. The recentincursion of bluetongue into northern Europe (France,Germany, the Netherlands and Belgium) demonstrates howa disease situation can change rapidly. For some of thesediseases no vaccines exist, whilst in other cases they existbut have not been licensed or authorised for use.

Authorisation of vaccinesEmergency vaccination strategies must be acceptable tostakeholders, who will want assurances that the vaccines tobe used at the very least meet regulatory requirements.European legislation requires that veterinary medicinalproducts must be authorised by means of a marketingauthorisation. Minimum requirements (in terms of quality,safety and efficacy) that medicines must meet to obtain anauthorisation are specified. The existence of a marketingauthorisation confirms that the vaccine is safe in terms ofanimal and human health and that it works.

If there is no authorised vaccine for use against the diseaseconcerned there is an exemption in European legislationfrom the requirement for an authorisation when a productis to be used in the event of a ‘serious disease epidemic’.The European Commission must be informed of thedetailed conditions of use. The term ‘serious diseaseepidemic’ is not defined in the legislation but clearlyapplies to outbreaks of FMD and other epizootic diseases.In these circumstances stakeholders will require assurancesthat the product is safe and of high quality and that thereare no risks to consumers from products derived fromvaccinated animals.

Consumer attitudes in generalPublic concernThere has been a dramatic increase in public concern overfood safety during the past decade, partly due to thenumber of food safety crises that have occurred, such asthose surrounding BSE, salmonella, Escherichia coli O157and dioxin. In the EU there is concern over the use ofgenetically modified products, eating food from animalstreated with antibiotics and the impact on human health ofthe development of resistance to antibiotics andanthelmintics used in animals. As a consequence there isincreasing public awareness and demand for highstandards, with consumers expecting food to be safe andfree of toxic substances, contaminants, additives, pesticideresidues and veterinary medicinal residues.

As awareness of food safety grows amongst the public thereis a greater need to provide assurances about safety andquality. Perceptions of the extent and prevalence of foodsafety hazards are constantly changing. Many food safetyhazards are well defined, but there remain differences ofopinion and a lack of understanding about the degree ofrisk posed by specific situations, such as emergencyvaccination, or by possible new hazards, especially thoserelated to new and advanced vaccines. It is natural forconsumers to feel some scepticism towards new andunfamiliar vaccines or situations when the perceived riskmay be different from the actual risk.


Special Eurobarometer on risk issuesIn 2005 the EU Directorate-General for Health andConsumer Protection and the European Food SafetyAuthority (EFSA) commissioned a survey in all EUMember States to assess how people perceive risk, focusingin particular on food safety. The survey results, publishedas a Special Eurobarometer on risk issues in 2006 (2)indicate that when people are asked to specifically cite anyproblems or risks associated with food, many thingsspontaneously come to mind but without any sense ofunanimity. Food poisoning comes to mind most often(16%), followed by chemicals (14%) and obesity (13%).For 7% of respondents food did not present any risks orproblems at all.

The report notes, however, that attitudes changed whenconsumers were reminded of the possible risks associatedwith food: concerns then appeared to be quite widespread.The main finding in the report is that people do notdifferentiate greatly between the various types of risks,although they are more likely to worry about risks causedby external factors over which they have no control. At thetop end of the ‘worry’ scale, consumers express concernregarding external factors that are clearly identified asdangerous (pesticide residues, new viruses such as AI,residues in meats, contamination of food by bacteria,unhygienic conditions outside the home). In the mid-range, one finds other external factors such asenvironmental pollutants (e.g. mercury), geneticallymanipulated organisms, food additives, animal welfare andbovine spongiform encephalopathy (BSE).

The fear of being endangered by food contaminated bytoxic substances, viruses, bacteria, and to a lesser extent by prions, is widespread among Europeans. On average,around a quarter of EU citizens are very worried aboutfood contamination. The level of worry does not varymuch between the food contamination issues included inthe survey. However, it is interesting to note from thereport that ‘close to three out of ten Europeans state thatthey are “very worried” about new viruses like AI and afurther 38% are “fairly worried” about this’. The reportnotes that survey participants gave these answers inresponse to a question that did not specifically focus on theway new viruses were transmitted, but talked aboutemerging viruses in general. This suggests that it is not aparticular method of transmission that worries the public,it is simply that they feel threatened by the existence ofnew ‘unknown’ viruses, whatever the means oftransmission.

The report does not contain specific comments about thevaccination of food-producing animals but it providesbackground information to explain why there could beconsumer concern about vaccination in certaincircumstances. The report indicates that when confronted

with possible risks associated with food, consumersidentify a wide range of concerns and tend to worry mostabout those factors which they cannot themselves control.It is clear that European consumers would be concernedabout the potential impact of vaccination if they had nocontrol over the products and particularly if products fromvaccinated animals were not labelled as such, therebyleaving them without the choice of whether or not to eatthem. To overcome these fears consumers needinformation which is reliable and from a trusted source.

Consumer attitudes to vaccinationSurvey in 2001The decision on whether to vaccinate in 2001 was linkedto the attitude of consumers to food products from FMDvaccinated animals. Various surveys conducted throughoutthe 2001 crisis provided equivocal answers. Only bytesting consumer behaviour in the market place could adefinitive view be obtained. The FSA made it clear by itsannouncement in late April that food products from FMDvaccinated animals posed no additional risks to food safety.Consumer organisations also concluded that it wasunlikely to be an issue for consumer choice and thatspecial labelling was not required. The Soil Association (aUK environmental organisation promoting sustainable,organic farming) and organic producers supported this view.

Small-scale surveys into public opinion in the UK during2001 indicated that most respondents considered that analternative to extensive culling in the case of an FMDoutbreak was needed. There was a widespread feeling thatconsideration should be given to a vaccination strategy if itwas practical and could be made to work. Whilst mostconsumers preferred vaccination as a method of avoidingextensive and widespread culling it would be necessary toconvince people that it could work and to overcome theirreservations about eating meat and other products fromvaccinated animals.

Most consumers interviewed had some reservations aboutthe idea of eating meat from vaccinated animals andneeded assurances that meat would be safe to eat. Even sosome retained doubts about the long-term safety of meatfrom vaccinated animals, which is due partly to the impactof the BSE crisis and the long incubation periods for priondisease in animals and humans. It was mainly motherswith younger children who were most resistant to eatingproducts from vaccinated animals. Most indicated thatgiven the option they would take meat from unvaccinatedanimals if the meat were labelled ‘vaccinated’ or


‘non-vaccinated’. To overcome these doubts it would benecessary to demonstrate safety and also put thevaccination in context, i.e. remind consumers that vaccinesare regularly used to control endemic diseases.

The advice from the FSA emphasised that produce fromanimals routinely vaccinated against other diseases couldbe safely eaten and that FMD vaccination was no different.Some of the respondents accepted that meat fromArgentina probably originated from vaccinated animalsand that it was consumed in the UK. Some consumersbelieved that produce from FMD vaccinated animals wassafe but preferred not to consume them if given the choice.Consumer nervousness is a real risk when vaccination isintroduced with full media coverage in an emergencysituation. This in turn creates fears that retailers would notpurchase products of vaccinated livestock, resulting in theanimals becoming valueless.

Scoping study into public perceptions A small scoping study (1) was conducted in 2003 intopublic perceptions concerning animal vaccination, usingthe 2001 FMD outbreak as a case study. The study hadthree components:

– an examination of press coverage of the issue ofvaccination during the epidemic

– data collection from subsets of the lay public likely torepresent differing viewpoints on animal vaccination

– an examination of the concerns expressed by foodmanufacturers (including farmers) and distributors aboutthe use of vaccination and how these relate to what theybelieve their customers, both domestic and commercial,would want or would reject.

The study established seven focus groups whose memberswere drawn from different backgrounds and werepredicted to have different reactions to the epidemic. Theauthor of the report recognised that focus groupmethodology typically does not permit tests of therepresentativeness of the findings for the population as awhole or discrete subsets of it, but the report indicated thatthe object of a focus group methodology was to capturesome of the diversity and complexity of views surroundingthe issue.

It was clear from the focus groups that there wasconsiderable diversity in public understanding ofvaccination. Interestingly, consumers in the focus groupsdid not indicate that they would have rejected productsfrom vaccinated animals (and food manufacturers did notmention consumer rejection as a possible reason for notvaccinating). This contrasts with the consumer surveycarried out during the epidemic, which suggested that the

public would reject food products from vaccinatedanimals. It may be that the public are more likely tosuppose that they would accept such food after the eventbut they may be more cautious during a major outbreak.

A range of general conclusions and lessons were describedin the study report. Those in relation to vaccination arelisted below:

– explaining complex scientific arguments to the public or to special interest groups in the middle of a crisis is notfeasible. This should be anticipated and the foundations of understanding the rationale for, and limitations of, vaccination should be established with the public priorto the next epidemic;

– informing the public requires their active engagement inthe process of gaining knowledge;

– there was evidence that the lay public interprets issuesconcerning animal vaccination in terms of understandingsof how human vaccination is used. This accounts for someof the difficulties in understanding the ‘vaccinate to kill’option. The anchoring of understanding of animalvaccination in human vaccination could be used as thebasis for developing future information provision;

– there was no evidence from the focus groups that thepublic would be unwilling to purchase or consume meatproducts from vaccinated animals. The press coverageechoed the FSA advice that such food stuffs would be safeto eat.

Eurobarometer survey into avian influenzaThe Eurobarometer survey conducted in March and April2006 (3) questioned over 25,000 EU citizens on AI, inparticular the risks it could pose to human health and howit spreads. The study revealed that most EU citizens arewell informed about AI but when it came to food safetythose surveyed were less sure. Whilst over 60% knew thatproperly cooked poultry meat and eggs could not transmitthe virus, only 47% believed it was true that meat fromvaccinated birds was not dangerous. It is of concern thatover 50% of those questioned did not believe that eatingmeat from vaccinated birds carries no risk to humanhealth. There was a marked difference between consumersin different countries, with those showing the highestawareness of the true facts coming from countries whereoutbreaks have occurred.

Research requirementsThe European Technology Platform for Global AnimalHealth published a strategic research agenda (SRA) in 2006(4). The SRA identified many of the consumer concernsabout technology and the use of veterinary medicines



(including vaccines) that have already been discussed inthis paper. It was considered important to investigate thebackground of these concerns by developing anunderstanding of public perception and societal views on arange of issues such as risk, benefits, products based onnew technology, new control measures and ethics. Thereappears to be a seemingly large information gap betweenpublic perception and the scientific situation in reality.

It is important to be aware of how society will viewadvances in technology and the use of new technologies.Not addressing these issues will lead to misunderstandingand mistrust. The actual rather than the perceived risk fornew technologies or existing technologies to controlanimal diseases must be discussed with the wider public toensure social acceptance. A number of studies into publicengagement and understanding have been carried out inthe past. The SRA recognised that societal studies wereneeded to assess the impact of new technologies oralternative eradication programmes which use veterinarymedicines.

The SRA identified a need to evaluate the most effectiveways to present new technology and new programmes tothe public. An evaluation of the risk communication andscience strategies available to present new informationwould be of considerable assistance in the development ofpublicly acceptable evidence-based policies to controlepizootic diseases.

Current developments in the United KingdomMany lessons have been learned since 2001, not least ofwhich is that the issue of vaccination should be settled atan early stage in the contingency planning process. SinceJanuary 2003, there have been extensive discussions andregular meetings with UK stakeholders to discuss theimplications of emergency vaccination and to obtainsupport from the whole of the food chain shouldemergency vaccination be required in future. Initially thesediscussions related to FMD, but a similar process is now inplace for AI. There are understandable concerns about themarketing of products post vaccination.

A statement summarising the situation on the use of FMDvaccination as part of disease control strategies has beenproduced by the UK government in cooperation withconsumer organisations. In the statement the FSAconfirmed that the consumption of products from animalstreated with authorised FMD vaccines ‘would not have anyimplications for food safety’. Furthermore BEUC, theEuropean Consumers’ Organisation, also stated inDecember 2004 that, ‘from the perspective of consumerorganisations there is no safety concern with products fromemergency vaccinated animals’. Consumer organisations inthe UK have confirmed that they support this view.

The statement records that discussion with retailers hasconfirmed that meat and milk from vaccinated animalswould not be separately identified, indeed there is noreason to do so. Vaccination is now accepted as one of theimportant options available in fighting an FMD outbreakand its implications are now seen as practical onesregarding the handling and marketing of products fromvaccinated animals rather than ones of the acceptability ofthose products to retailers and consumer groups.

ConclusionsA review of the available literature does not provide a greatdeal of specific information on consumer attitudes tovaccination of food-producing animals. Experiences in theFMD crisis and subsequently with AI indicate that there ispotential public concern over the consumption of productsfrom animals vaccinated as a control measure during amajor outbreak of disease. This contrasts with the apparentlack of concern about routine vaccination against a widerange of diseases in most food-producing species. This isnot unexpected as there is little public discussion onvaccination of food-producing animals during periodswhen there are no active national vaccination campaigns.Furthermore, the public generally identifies withvaccination in a favourable manner due to the benefits tohuman health and the positive impact of vaccination incompanion animals.

An analysis of a number of linked surveys indicates thatconsumers are most concerned when actions take placeoutside their own control and where they have no choice.It would also appear that in the height of an epidemic thereis increased sensitivity to the potential impact of thecontrol measures. Even though the media often reflects theadvice from the food safety authorities, the fact that thesubject of food safety is constantly raised impacts on publicconsciousness and often leads to increased concern of theunknown.

Whilst many aspects of the safety of vaccines are ascientific issue, public perception is equally important inthe policy-making process, especially if the issue has a highpolitical impact. The discussions around vaccinationagainst FMD, CSF and AI show that there are potentiallynon-scientific concerns over vaccination. Many agree onthe value of existing or new vaccines but the main obstacleto their success may be the issue of public acceptance. Lackof societal acceptance can also be a barrier to the development and use of new technologies to control disease.

It is important to anticipate this type of debate and toensure that understanding and agreement is reached beforevaccination is used to control outbreaks of epizootic

disease. A number of important steps can be taken tomaintain public confidence. These include:

– developing a vaccination policy for inclusion in thecontingency plans before an outbreak occurs andidentifying the circumstances in which vaccine will be used

– discussing the vaccination policy with all stakeholders

– obtaining public support for the control policy

– ensuring that vaccines to be used have a licence ormarketing authorisation for use in the country concerned

– providing and discussing safety information with allstakeholders if an unauthorised vaccine needs to be usedin an emergency

– avoiding a two-tier system by not separately identifyingproducts from vaccinated and unvaccinated sources andissuing clear statements that products from vaccinatedanimals will be used as part of the general food supply

– providing unequivocal and authoritative assurance thatvaccination poses no threat to human health and thatproducts from vaccinated animals are safe to eat

– ensuring that national and international independentbodies that are respected by the consumer issue statementsto reassure consumers that the consumption of productsfrom vaccinated animals poses no risk to human health

– ensuring that any statements are endorsed by theproducer, retailer and consumer organisations

– developing a communication strategy involving allstakeholders to ensure that consistent messages onvaccination are provided by all stakeholders before andduring an outbreak in which emergency vaccination maybe used

– implementing a concerted campaign organised by thegovernment and the industry to convey the safety messageswhenever emergency vaccination is to be used to control adisease outbreak.

Public disapproval of control measures such as massslaughter to control epizootic diseases will continue tocontribute to a drive for vaccination as an alternativemeasure. As vaccination is seen as ethically and morallyacceptable public acceptance of such a measure would behigh. However, the results of surveys are equivocal and itis not always clear that consumers are willing to eatproducts from vaccinated animals. It is essential to have aclear and agreed policy on the use of vaccines against FMDand other diseases that can cause serious economicproblems. Clear advice to consumers by respectedindependent bodies such as the FSA in the UK and EFSAis critical to ensure a successful vaccination policy.Consumer confidence is essential for any emergencyvaccination programme and a major public relationsprogramme would be needed.


Comportement des consommateurs à l’égard de la vaccination des animaux destinés à l’alimentation humaine

J.M. Scudamore

RésuméL’épisode de fièvre aphteuse survenu en 2001 au Royaume-Uni a mis en évidencela nécessité de mettre en œuvre une politique de vaccination à l’acmé del’épizootie. En raison de l’ambiguïté des résultats des enquêtes d’opinionréalisées jusqu’alors, il était impossible d’apprécier le degré de méfiance desconsommateurs à l’égard des aliments issus d’animaux vaccinés. Une enquêterécente sur l’influenza aviaire a révélé que si les consommateurs européens sontbien informés au sujet de la maladie et des méthodes de lutte applicables, plusde 50 % des personnes interrogées ne sont pas disposées à consommer de laviande issue de volailles vaccinées. Il n’y a pas d’informations précises surl’opinion des consommateurs à l’égard de la vaccination régulière visantd’autres maladies. Les préoccupations du public semblent s’accentuer pendantles périodes de crise, qui ont une plus forte couverture médiatique. Ledéveloppement de nouveaux types de vaccins doit s’accompagner de mesures


visant à rassurer les consommateurs quant à l’innocuité et à l’utilisation de cesproduits. L’auteur examine ces questions et fait quelques recommandationspratiques sur les moyens de rassurer le public en cas d’application de lavaccination d’urgence pour lutter contre les maladies animales.

Mots-clésAttitude des consommateurs – Confiance du public – Influenza aviaire – Leçon del’expérience – Préoccupation des consommateurs – Sécurité sanitaire des aliments –Vaccination.

Actitud del consumidor frente a la vacunación de animalesdestinados al consumo humano

J.M. Scudamore

ResumenEl brote de fiebre aftosa que en 2001 asoló el Reino Unido fue un episodio sinprecedentes, frente al cual hubo que obtener una vacuna justo en el momentoálgido de la epidemia. Dados los resultados poco claros de las encuestas, no fueposible determinar el grado de preocupación de los consumidores por el hechode ingerir alimentos procedentes de animales vacunados. De una recienteencuesta relativa a la influenza aviar se desprende que el gran público europeoestá bien informado sobre la enfermedad y su control, aunque más del 50% delos encuestados serían reacios a consumir carne procedente de avesvacunadas. No existe mucha información específica sobre la opinión de losconsumidores acerca de la vacunación sistemática contra otras enfermedades.Su inquietud parece acrecentarse en las situaciones de emergencia, cuando losmedios de comunicación ofrecen abundante información sobre el tema. Con laaparición de nuevos tipos de vacuna, será preciso ofrecer al consumidor másgarantías sobre el uso y la inocuidad de tales productos. Además de examinartodas estas cuestiones, el autor formula recomendaciones prácticas paraofrecer al gran público las debidas garantías a la hora de proponer unavacunación de emergencia con fines zoosanitarios.

Palabras claveActitud del consumidor – Confianza del gran público – Enseñanzas extraídas – Fiebreaftosa – Influenza aviar – Inocuidad de los alimentos – Preocupación del consumidor –Vacunación.

References1. Breakwell G.M (2003). – Public perceptions concerning

animal vaccination: a case study of foot and mouth 2001.Available at: http://www.defra.gov.uk/science/documents/publications/mp0140.pdf (accessed on 12 September 2006).

2. European Commission (2006). – Special Eurobarometerreport number 238 on Risk issues. Available at:http://ec.europa.eu/public_opinion/archives/eb_special_en.htm (accessed on 12 September 2006).

3. European Commission (2006). – Special Eurobarometerreport number 257 on avian influenza. Available at:http://ec.europa.eu/public_opinion/archives/eb_special_en.htm (accessed on 12 September 2006).

4. European Technology Platform for Global Animal Health(2006). – Strategic Research Agenda: societal acceptance oftechnology, 44-45. Available at: http://www.ifah.be/Europe/euplatform/SRA_May06.pdf (accessed on 12 September2006).



Vaccines for immunological

control of fertility in animals

C.M. Hardy & A.L. Braid

Commonwealth Scientific and Industrial Research Organisation

GPO Box 1700, Canberra, ACT, 2601, Australia, and Invasive Animals Cooperative Research Centre, 3D1

University of Canberra, ACT 2601, Australia. E-mail: [email protected]

Summary

Fertility control has gained considerable momentum as a management tool to

regulate populations of captive and wild animals and to control aggressive

behaviour or improve meat quality in livestock. Anti-fertility vaccination

(immunocontraception and immunocastration) is a humane alternative to

methods that rely on surgical or chemical sterilisation and lethal control. Two

types of experimental immunocontraceptive vaccine have been registered for

field use in animals. They contain either porcine zona pellucida (PZP) proteins

extracted from pig ovaries or synthetic conjugated gonadotrophin releasing

hormone (GnRH) peptides. These vaccines require repeated injections and are

limited to captive or small populations of free-ranging wild animals. Alternative

immunocontraceptive vaccines are actively being developed either to improve

efficacy or enable large numbers of wild animals to be targeted. Some employ

live genetically modified viruses to deliver immunocontraception and have

proved successful under laboratory conditions. The relative merits, risks, social

acceptability and regulations controlling the use of existing and novel animal

immunocontraceptives are reviewed.

Keywords

Animal contraception – Ethics – Genetically modified organisms – Legislation – Risk.

Introduction

Fertility control, either by surgical, chemical orimmunological means has been demonstrated to be aviable alternative to lethal methods of controlling animalpopulations (9, 21, 38). The appropriate approaches tocontrolling fertility depend on the target species andintended outcome and include consideration of factorssuch as relative efficacy and safety, economic value,delivery mechanism, non-target and environmental effectsand social acceptability (5, 9, 25, 58). Each approach raisesethical (48) and social acceptability issues (11).

In contrast to vaccines that protect against infectiousdiseases, anti-fertility vaccines aim to induce immuneresponses (antibodies or cellular immunity) againstmolecules naturally present in an individual. These include

proteins or chemicals involved in the production ofgametes and sex steroids, release of viable sperm or eggs,fertilisation, implantation and subsequent embryodevelopment (20). Immunological approaches tocontrolling fertility lead to three different outcomes,depending on the reproductive functions that are affected.These outcomes are contraception, castration orinterference with gestation (5, 25, 60).Immunocontraception describes the prevention offertilisation, either by blocking the release of sperm or eggsor their subsequent interactions in the female reproductivetract. It can also be considered to include immunologicalinterference with receptiveness of the uterine environmentto embryo implantation in females. Immunocastration onthe other hand describes autoimmune responses thatdirectly affect the structure and function of the gonads ineither sex, thus interfering with their ability to producegametes and sex steroids. The third target for

immunological interference with reproduction is post-implantation embryo development and survival(maintenance of pregnancy).

Immunocontraception and immunocastration can beapplied to both sexes. Immunocontraception ideally isreversible once vaccination ceases and should not affectlevels of circulating sex hormones or libido in anydiscernable way (1). Immunocastration, apart frominfertility, causes a reduction in sex hormone levels andalterations to metabolism. It is generally applied in caseswhere modification to behavior such as aggression controlis required (19, 43, 65). Interference with pregnancyapplies only to females and is linked to health risks for themother and fetus, particularly late in gestation. It can alsoappear as an undesired side effect in some othercontraceptive approaches and raises ethical issuescomparable to those associated with chemical or surgicaltermination of pregnancy (2, 60).

Anti-fertility vaccines are intended to break immunetolerance to ‘self antigens’ and so pose a real risk ofinducing unintended long-term autoimmune disease (69).Many potential target molecules are either directly requiredfor physiological activities other than reproduction or havefeatures in common with molecules with differentfunctions. Vaccines against fertility must thereforeselectively target antigens to minimise the risk ofimmunological cross-reactions and avoid unintendedinterference with other physiological processes (61).

Non-immunological fertility controlConventional methods of regulating fertility in a widerange of animals include physical separation, chemicalcontraception, surgical sterilisation and barrier methods(5, 9, 21, 42). All these approaches have certainadvantages, but also suffer from drawbacks (24, 57).Physical separation, whilst highly effective, can affect thebehaviour of animals, particularly males. Surgicalsterilisation (castration and hysterectomy) andcontraception (tubal ligation) are highly effective forcaptive animals when irreversible infertility is required.However, this approach generally requires veterinary skillsand since it involves invasive procedures, causes pain,discomfort and carries the risk of infection in the shortterm. They are not readily applicable to wildlife. Longterm, castration prevents sex steroid production and affectsmetabolism. Tubal ligation is highly effective where there isa need to retain hormonally-dependent social hierarchies,but is not effective for controlling undesirable sex-relatedbehaviour. Chemical contraception or castration (usingoral or injectable implants) can be a highly effective and

reversible method for animal applications (5) and oraldelivery of chemical contragestatives has also been usedwith mixed success to control populations ofoverabundant bird species (87). In humans, thetechnology for safe female chemical contraception is welladvanced (7), but remains elusive for males (29). Chemicalcontraception can be associated with metabolic side effectsand severe pathology in some species following prolongeduse (18, 55). In livestock, the presence of steroidmetabolites in the animals can affect meat quality (40, 71,76) or growth rates (34). The barrier method andintrauterine devices are effective and have been used withhigh-value animals (dogs, monkeys and camels) but havenot been widely adopted (82). It has been recognised thatalternative forms of contraception need to be made morewidely available both for human (58) and animal use (24).

Immunological fertility control

Adjuvant vaccines

Most vaccines that have been used for routine fertilityregulation in captive or small groups of free-ranginganimals are comprised of various formulations of proteinsor peptide antigens mixed with adjuvants. The mosteffective antigens fall into three main groups:

– those derived from the gonadotrophin releasinghormone (GnRH), the luteinizing hormone releasinghormone (LHRH) and the follicle stimulating hormone(FSH)

– the structural glycoproteins forming the zona pellucida(ZP) that surrounds the oocyte

– the ovary and/or placental hormones, e.g. luteinizinghormone (LH) and human chorionic gonadotrophin(hCG) (19, 27, 30).

Many other antigens (natural and recombinant proteinsand synthetic peptides), most notably derived from sperm,also have immunocontraceptive potential based on a largenumber of experimental studies, but so far appear lessefficacious than hormonal or ZP antigens (31, 60).Vaccines based on GnRH and pig ZP (PZP) have provedpractical to use in a range of captive and wild animalswhere direct injection or darting is feasible, whereas hCGvaccines are restricted to primates (25). Immunisationagainst GnRH prevents LH and FSH synthesis and leads toatrophy of the ovaries and testes. This generally inducesreversible castration in males and females, although it canlead to irreversible infertility in rats (49) and lesions in thehypothalamus in pigs (54). However, immunising againstthe beta subunit of hCG or PZP also causes reversiblecontraception by preventing fertilisation and gametedevelopment in the case of PZP (8) or early embryo


survival in the case of hCG (3, 73, 78). All these self-antigens require potent adjuvants and repeatedimmunisations to generate their effect and overcomeimmune tolerance. The antigens and some adjuvants incurrent use (particularly Freund’s complete, Freund’smodified and other oil-based formulations) are known tobe irritant and are associated with side effects that varysignificantly in their nature and intensity, depending on thespecies and sex targeted (27, 33, 56).

Virally vectored immunocontraception

A relatively recent development is the use of geneticallymodified viral vectors to produce anti-fertility biologicalcontrol agents. In this approach, termed virally vectoredimmunocontraception (VVIC), the gene for a fertilityantigen is inserted into the genome of a replicationcompetent virus. The recombinant virus then expresses theantigen in infected animals and induces a contraceptiveautoimmune response (80). The viral vectors can either be used for the direct inoculation of individuals or they canbe administered in a way that allows the vectors to betransmitted (self-dissemination) among free-rangingwildlife and pest animals. These vaccines are intended tosupplement current control practices of shooting, trappingand poisoning for wide-scale problem species. VVIC hasyet to be tested outside laboratory and quarantinecontainment, but it shows considerable promise as abiological control for wildlife (31, 32).

Virally vectored immunocontraception has been testedwith varying degrees of success in laboratory trials in arange of species; vaccines tested include recombinantvaccinia virus in rats and foxes, myxoma virus in rabbits,canine herpesvirus in foxes, and ectromelia virus andmurine cytomegalovirus in mice and rats (32). Theapproach has proven highly successful in the laboratoryand infertility rates approaching 100% have been achievedin naïve mice infected with recombinant viruses expressingmouse ZP3 after only a single inoculation (35, 44, 67).Sterility, as well as reversible long- and short-term, singleshot contraception, without the need for adjuvants, appearfeasible using this approach.

Nematode-vectored immunocontraception

New Zealand Landcare Research and AgResearch aredeveloping a parasitic nematode (Parastrongyloidestrichosuri) for biological control of possums in NewZealand (17). The ability to produce transgenic P. trichosurihas been established (28) and it appears amenable for useas an immunocontraceptive vaccine vector in the field asthe parasite is specific to possums and is able to establishrapidly in wild possum populations (17).

Other immunological approaches

Several studies have explored the use of bacteria as deliveryvectors for immunocontraception (13, 50, 75, 88),although efficacy has been disappointing. DNA vaccines(14, 59, 62, 86), recombinant plant viruses (26) andrecombinant bacteriophages (1) have also been trialed inmice and primates with some success.

Risks of exposure to anti-fertility vaccines for human handlers

The long-term safety and reversibility of hCG, FSH andGnRH immunocontraceptive vaccines have been directlyassessed in humans. Various formulations of hCG and FSHvaccines have also undergone fertility trials in humans (19,60), although clinical human trials with a GnRH vaccinewere restricted to male patients with advanced carcinomaof the prostate (77). The potential safety issues for humansat risk from unintentional exposure to most contraceptivevaccines being used in animals can only be inferred fromprimate or other animal studies. As someimmunocontraceptive antigens (particularly those basedon FSH and GnRH) have the potential to affect fertility inboth males and females, precautions should be taken tominimise the risk of accidental exposure to these agentswhen administering them to animals. However, repeated orprolonged exposure by accidental injection would berequired in most cases to induce long-term effects inhuman handlers. A recent comprehensive coverage of therelative merits of currently available chemical andimmunological agents for animal contraception, includingthe procedures and precautions that should be taken whenhandling each of these products has been made availableon the website of the AZA Wildlife Contraception Center atSaint Louis Zoo in the United States of America (USA)(http://www.stlzoo.org/downloads/CAGrecs2006final.htm).

The use of PZP antigen may pose an additional risk tohuman handlers as they must be given using eitherFreund’s complete or modified adjuvants (27). Adjuvantssuch as these contain a combination of mycobacteria andmineral oil that have been reported to cause severelocalised lesions in people following accidental self-inoculation (84). The PZP antigens themselves are alsoassociated with the appearance of adverse side effects insome species, including T-cell mediated ovarian damage(oophoritis) and inhibition of steroid production (6, 64,68, 74, 81). In other species, there do not appear to be anysignificant PZP-related side effects in somatic tissues afterPZP immunisation (8).

Regulatory issuesThe various national regulatory frameworks that governthe use of animal contraceptives are complex (39). Each


country has its own set of regulations and legislations,although many international arrangements are also inplace, and researchers or practitioners are required toadhere to their own jurisdiction’s guidelines.

Vaccines against GnRH (VaxstrateTM and ImprovacTM) havebeen registered for control of libido and sex steroidproduction as well as increased growth in livestock such aspigs, sheep and cattle in Australia (19, 25). Another GnRHvaccine (GonaConTM) is registered as an experimentalwildlife vaccine by the United States Food and DrugsAdministration (FDA). It is undergoing a number of fieldstudies in the USA, principally in white-tailed deer, by theNational Wildlife Research Center (NWRC) in the UnitedStates Department of Agriculture (USDA) Wildlife Services(20, 25, 51, 52). A vaccine derived from whole solubilisedPZP (SpayVacTM) is also registered as an investigational newanimal drug by the FDA for use in captive zoo animals andcertain wildlife applications (27).

There are considerable regulatory and social acceptabilityissues linked with the use of live genetically modifiedimmunocontraceptive virus vaccines. These include theperceived risks associated generally with the use ofgenetically modified organisms and concerns aboutspecies-specificity, efficacy, safety, choice and internationalimplications for trade and biodiversity (4, 45). Thepresence of strict regulatory controls governing anyintended registration of VVIC products has meant that thistechnology has not yet been approved for use in anycountry outside containment facilities for handlinggenetically modified organisms.

Ecological issuesIt has been proposed that the widespread use ofimmunocontraception in wildlife may lead to thedevelopment of genetic resistance or heritable immunedysfunctions that reduce the ability of animals in the targetpopulations to combat diseases (15, 16, 46, 57). However,most debate on applying immunocontraceptive productsto wildlife relates to the relative environmental impacts ofpopulation control using sterility versus lethal methodsand the theoretical risks of affecting non-target species inthe case of viral-vectored immunocontraceptive agents(10). The actual impacts of behavioural modifications inwildlife and the risk to non-target species still need to bedetermined as few long-term data sets are available,although most authors concede that fertility controlmethods such as immunocontraception so far appear likelyto provide significant environmental benefits over lethalcontrol (9, 10, 11, 13, 38, 52, 80). Positive benefits ofimmunocontraception have been reported to includeweight gain and increased longevity in populations of wildhorses treated with PZP (38) and immunocontraception

with GnRH in bison is being explored as a possible meansof controlling the transmission of brucellosis to adjoiningpopulations of cattle in the USA (52).

Social and ethical issuesThe ethical principles underpinning the rights, welfare andfertility control of captive and free-ranging animals havebeen debated (53, 85). It is beyond the scope of this paperto address the rights of animals to live their lives withouthuman interference (66), whether animals should havefreedom to express normal behaviour (23), or whetheranimals suffer from imposed castration or contraception(83). It is, however, understood that separation of malesfrom females is the preferable means for controlling fertilityin livestock and zoos. However, animal welfare issues andthe ethics of imposed fertility control of free-living andcaptive wildlife will be discussed.

The use of immunocastration and immunocontraceptionhas been recognised as providing animal welfare benefitsrelative to alternative procedures (63, 66, 70, 80). Inproduction animals, the animal welfare benefit is theprovision of alternatives to the on-farm surgical removal ofan animal’s gonads, usually undertaken withoutanaesthetic. In free-living wildlife, fertility control isrecognised by animal welfare proponents as preferable tomost lethal methods of controlling populations (63, 66).

Production animals

In the pig industry, to avoid boar taint due to fatandrostenone in the meat, male piglets are routinelycastrated without anaesthetic during the first fews weeks oflife. European Commission Directive 2001/93/EC stillallows castration of piglets less than seven days of agewithout anaesthesia, even though research has shown thatpain associated with castration is not affected by age (79).There have been campaigns by the Royal Society for thePrevention of Cruelty to Animals (RSPCA) in the UnitedKingdom (UK), and others, to ban the practice.Alternatives include no castration and early slaughter,surgical castration under general or local anaesthetic,immunocastration and sex-sorting of sperm for theselective production of female pigs (41).Immunocastration, using vaccination against GnRH(ImprovacTM CSL, Australia) has been shown to avoid thepain associated with surgical castration, suppressandrostenone and improve the yield of lean meat invaccinated pigs compared to those surgically castrated(36).

Immunocontraception with another GnRH vaccine(VaxstrateTM. Arthur Webster, Australia) has been applied


commercially as an alternative to surgical speying ofheifers. This procedure is applied to stop them becomingpregnant whilst they are being fattened for slaughter underfree-ranging conditions. Although originally promoted forthe animal welfare benefits inherent in avoiding surgicalspeying without anaesthesia, the vaccine is no longercommercially available due to the additional costassociated with mustering of cattle for boostervaccinations, the cost of the vaccine itself and the lack ofeffect in stopping a proportion of heifers from cycling andbecoming pregnant (12, 37).

Zoo animals

Population management in zoos is a particularly difficultissue as there is an imperative to allow for naturalbehaviour in captive animals, including reproduction, andto conduct successful breeding programmes while notproducing surplus animals (83). Immunocontraceptionwith PZP has been used succesfully in a range of zoospecies. However, safety concerns preclude its use inpregnant animals and long-term effects have beendescribed that include disruption to the reproductiveendocrine system in some species. The time taken toreturn to fertility also varies between species (27).

Free-living wildlife

There are a range of ethical issues associated with thediffering strategies used to control free-living animals inmost countries and three different ethical positions onwildlife population control have been taken (66). These arethe Animal Rights position, i.e. an animal’s right to controlits own life should not be interfered with in any way; theEnvironmental or Natural position, i.e. animal populationscan only be controlled by predation or hunting and; theAnimal Welfare position, i.e. populations should becontrolled by non-lethal methods such asimmunocontraception.

Another ethical position has been taken in countries withlarge numbers of introduced, non-indigenous animals thatare serious pests. These pests include rabbits (Oryctolaguscuniculus), foxes (Vulpes vulpes) and cats (Felis domesticus)in Australia and ferrets (Mustela putorius), stoats (Mustelaerminea) and possums (Trichosurus vulpecula) in NewZealand. The large populations of non-indigenous specieshave severe negative impacts on native plants and animals.The control of these populations is undertaken for tworeasons: their economic impact on agricultural production,and their damage to the environment. The large numbers

of animals involved, the widespread use of non-targetspecific toxicants and the use of lethal disseminatingdisease agents has led to considerable debate on the ethicsof controlling pest animals (15, 45, 63, 72, 80). Acontentious ethical position for controlling thesepopulations has been advocated that combines theprinciples of ecocentrism and animal welfare (22, 47).Ecocentrism holds that ecosystems have their own intrinsicvalues and moral standings which can be equal to orgreater than individual species, including humans. Underthis framework, the conservation value of the indigenousecosystem (native plants and animals) requires the controlof the non-indigenous populations and overrides theanimal rights ethic of equal consideration of the interests ofall sentient beings (72). However, it is considered that ananimal welfare ethic should also be applied and control ofnon-indigenous sentient animals should be undertaken bythe most effective and humane methods available, such asimmunocontraception.

ConclusionsImmunocontraception and immunocastration aredeveloping into viable management tools for fertilityregulation in both captive and wild animals. In particular,fertility control by immunological means provides anattractive and ethically supported alternative to surgicalsterilisation, as it is considerably less invasive and morehumane. Nevertheless, apart from PZP vaccination in somezoos and promotion of GnRH vaccines as an alternative tocastration in male piglets, immunocontraceptive vaccinesare only available for experimental use. The lack ofpenetration of existing vaccines into many markets, suchas companion animals, is due to a combination of factors,including uncertainties surrounding their long-termefficacy and safety, the requirement for repeatedinoculation using potentially unacceptable adjuvants andrelatively high production costs. However, if these issuescan be resolved, the next generation ofimmunocontraceptive vaccines should be able to provideconsistent, long-term infertility after a single applicationand provide realistic alternatives to chemical and surgicalmethods.

AcknowledgementsThe authors wish to thank Tony Robinson for criticallyreviewing the manuscript.


Les vaccins et le contrôle immunologique

de la fécondité chez les animaux


Résumé

Le contrôle de la fécondité a pris un élan considérable, en tant qu’outil de

gestion des populations des animaux en captivité et sauvages et moyen de

contenir les comportements agressifs et d’améliorer la qualité de la viande issue

des animaux de rente. La vaccination visant à contrôler la fécondité

(contraception et castration immunologiques) est une alternative aux méthodes

basées sur la stérilisation chirurgicale ou chimique ou sur le contrôle létal des

populations. Deux types de vaccins expérimentaux ont été enregistrés pour la

contraception immunologique des animaux, en vue d’une utilisation sur le

terrain. Ils contiennent soit des protéines prélevées de la zone pellucide (PZP)

d’ovaires de truie, soit des conjugués de peptides synthétiques de l’hormone

stimulatrice de la gonadotrophine (GnRH). Ces vaccins devant être administrés

régulièrement, leur utilisation n’est envisageable que pour des animaux

maintenus en captivité ou pour des populations limitées d’animaux sauvages.

D’autres possibilités de contraception immunologique sont à l’étude afin

d’améliorer l’efficacité de la méthode ou de permettre son utilisation sur des

populations plus nombreuses d’animaux sauvages. Certaines de ces méthodes,

basées sur l’utilisation de virus vivants génétiquement modifiés pour empêcher

la conception, ont donné de bons résultats au laboratoire. Les auteurs examinent

les mérites et les risques respectifs des différentes méthodes de contraception

immunologique disponibles ou en voie de développement, ainsi que

l’acceptation sociale et la réglementation applicable en la matière.

Mots-clés

Contraception animale – Éthique – Législation – Organisme modifié génétiquement –

Risque.

Vacunas para el control inmunológico de la fertilidad en animales


Resumen

El control de la fertilidad ha cobrado un notable impulso como instrumento de

gestión para regular las poblaciones de animales salvajes y en cautividad, y

también para controlar la agresividad o mejorar la calidad de la carne en el

ganado vacuno. Las vacunas anti-fertilidad (inmunoanticoncepción e

inmunocastración) constituyen una alternativa suave a los métodos basados en

el sacrificio o en la esterilización quirúrgica o química. Hoy en día están

registrados dos tipos de vacuna inmunoanticonceptiva para una utilización

experimental sobre el terreno, constituidas en un caso por proteínas de zona

pelúcida porcina, extraídas a partir de ovarios de cerdo, y en el otro caso por un



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conjugado sintético de péptidos de la hormona liberadora de gonadotropina

(GnRH, por sus siglas en inglés). Estas vacunas requieren repetidas inyecciones

y sólo pueden usarse en el caso de poblaciones en cautividad o de un pequeño

número de animales salvajes en libertad. Están en marcha procesos para

obtener vacunas alternativas, que mejoren la eficacia de las anteriores o puedan

administrarse a grandes poblaciones de animales salvajes. En algunas de ellas

se emplean virus vivos genéticamente modificados para lograr la

inmunoanticoncepción, método que se ha demostrado eficaz en condiciones de

laboratorio. Los autores examinan las ventajas y riesgos, la aceptabilidad social

y los reglamentos que rigen el uso de los métodos de inmunoanticoncepción

animal ya arraigados o de reciente aparición.

Palabras clave

Contracepción animal – Ética – Legislación – Organismos genéticamente modificados –

Riesgo.


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470 Rev. sci. tech. Off. int. Epiz., 26 (2)


Animal vaccination and the veterinary

pharmaceutical industry

D. O’Brien (1) & S. Zanker (2)

(1) International Federation for Animal Health (IFAH) – Europe, Rue Defacqz, 1 B-1000 Brussels, Belgium

(2) International Association for Soaps, Detergents and Maintenance Products (AISE), Avenue Herrmann

Debroux 15A, 1160 Brussels, Belgium

Summary

The market for veterinary vaccines is spread across species but it is limited in

size and the development of vaccines is becoming more complex and expensive.

Vaccines are amongst the most effective means of preventing disease in both

animals and humans. In many cases, diseases have been eradicated or their

impact on animal health and welfare greatly reduced. It is an ethical

responsibility to ensure the availability of a wide range of vaccines even where

the market needs to be financially supported, as in the case of less common

animal species and those with less common conditions (commonly referred to by

the acronym MUMS: Minor Use and Minor Species). Mass slaughter is

becoming unacceptable to society and we must move to a ‘vaccinate to live’

policy wherever possible. We need to use vaccines to avoid the high costs of

disease and to enhance food safety. In developing vaccines, we need to

minimise animal testing. In addition, we need to ensure that the public accept the

use of vaccines in food-producing animals as a means of protecting the health

and welfare of all animals. As we look to the future, vaccines will be vital to

ensure our ability to provide more food to a growing global population. The

European Technology Platform for Global Animal Health has a key role to play in

identifying key research priorities.

Keywords

Disease – Ethical approach – Food safety – Health – Research – Veterinary vaccine –

Welfare.

The global veterinary vaccine marketIn 2004, the international veterinary vaccine market wasworth US$3.1 billion (i.e. 21% of the total veterinarymedicine market, which is valued at US$15 billion). Forty-one per cent of the market was based in the Americas, 37% in Europe and 22% across the rest of the globe. Table I provides a breakdown of the global veterinaryvaccines market in terms of species.

Table I

A breakdown of the monetary value of the global veterinary

vaccines market in 2004

Species Value in US$ billions

Livestock 1.50

Poultry 0.68

Other 0.92

Source: Wood Mackenzie Ltd, 2004 – Global Veterinary Biologicals

Market by Region and Species in 2004

Developing a vaccine: the process

Put simply, the process of developing a vaccine involvesidentifying a disease target, isolating the disease organism,growing it in eggs or cells, treating it physically orchemically so that it does not cause disease (inactivatedvaccines) or attenuating virulent characteristics of thestrain (live vaccines) and then administering it to theanimal. The result is an immune response that protects theanimal against the disease.

Modern genetics technology allows for more possibilitiesand options such as taking genes from the diseaseorganism, inserting them into harmless viruses, growingthe viruses and then administering the live virus to theanimal to create the immune response. In addition, genesmay be added to a known virus that is harmless, the virusmay then be grown, treated in a manner that kills the virusand the resultant material may be used as a vaccine.Finally, a second disease may be identified, genes from thefirst disease may be added to the second disease, cultivatedand the resultant treated material may be used to vaccinateagainst two diseases.

In many cases, industry develops vaccines in cooperationwith universities, institutes and other bodies, therebycombining its expertise with that of third parties. This isincreasingly necessary as new scientific disciplines develop(such as in the area of genomics), as it is much moreefficient to combine resources than for each party to haveits own specialists.

Costs of developing

a vaccine: benchmark data

Industry surveys indicate that the time taken to develop avaccine varies across species. The process may take eight toten years for brand new products. During this period, thedevelopment of the product is coupled with studies todemonstrate the safety, quality and efficacy of the product.The product must be formulated in a way that facilitatesuse and optimises efficacy, e.g. by including an adjuvant tostimulate a maximum immune response that lasts for areasonably long period of time.

The cost of this process also varies, but it is estimated thatthe average cost is US$50 million. As technology developsin complexity, regulatory requirements also become morecomplex, with both factors leading to an increase in the

cost of developing vaccines. This is in contrast to the valueof food-producing animals, which is tending to declineover time.

It is clear, therefore, that commercial vaccine productioncan only be undertaken for diseases that generate salescovering the cost of development, along with some profits.As a result, we have disease problems where thedevelopment of vaccines must be supported by publicauthorities, e.g. anthrax and botulism.

The benefits

of animal vaccination

Vaccination is part and parcel of good husbandry andmanagement. Vaccines are amongst the most effectivemeans of preventing disease in both animals and humans.Preventing disease protects the health and welfare of theanimals (i.e. less mortality and fewer animals that survivethe disease but are negatively impacted for the rest of theirlife, e.g. with impaired lung function), helps to prevent thespread of disease to humans (e.g. salmonella vaccinationensures high quality food is produced from healthyanimals) and helps to protect the environment, as feweranimals are required for food-producing purposes.

Vaccines, coupled with diagnostic tests, eradicationprogrammes and surveillance, help to eradicate diseases,e.g. foot and mouth disease (FMD), rabies and Aujeszky’sdisease in many EU countries. They also help to reduce theannual 17% loss of production associated with disease inanimals. With globalisation, the potential for diseases totravel with animals, animal products and humans is greatlyincreased, as was seen during the 2003 outbreak of severeacute respiratory syndrome (SARS), thus the role ofvaccines is becoming increasingly important. TheEuropean Technology Platform for Global Animal Health(ETPGAH) is actively involved in identifying prioritydiseases and research needs so that our ability to controldiseases into the future will be increased. Coordination ofresearch on a global basis via the ETPGAH has thepotential to deliver significant benefits to society in themedium to long term. The advantage of being able toeradicate diseases, e.g. avian influenza, at source and soprevent them becoming global threats is clear and thebenefits to society are huge.

Socio-ethical issues

The benefits of vaccination are clear, but there are severalissues to deal with when developing vaccines for animalsand each will be examined in this section.


Vaccine availability

In the context of vaccines for less common animal speciesand those with less common conditions (often referred towith the acronym MUMS: Minor Use and Minor Species),the issue of availability is very real. Where there is a raredisease in a major species, such as FMD, anthrax orbrucellosis, public funding must be made available if wewish to develop a vaccine as opposed to relying onantibiotic treatment of sick animals. It is ethicallyunacceptable to allow animals to become ill if we havetools, such as vaccines, to prevent illness. What price issociety willing to pay to follow this ethical approach? Inthe case of minor species such as goats, fish, rabbits ordeer, again, third party intervention is necessary if vaccinesare to be developed. This could come in the form of publicfunding or the funding of the development of a vaccine,under contract, by groups of farmers who pool funds. Thealternatives to vaccination are to treat animals that becomeill or to stop producing some of these species for foodpurposes.

Mass slaughter

The outbreak of FMD in the United Kingdom (UK) in2001 (other areas of the globe are likely to be similarlyimpacted) represented a turning point in policy in theEuropean Union (EU). It is no longer acceptable to thepublic to engage in the mass slaughter of animals that waswitnessed during that outbreak. Instead of focusingexclusively on prevention and eradication, vaccination isnow seen as a tool in the armoury to fight exotic diseases.This change in policy has become known as the ‘vaccinateto live’ policy. Whilst a stamping out approach is still themost widely implemented strategy to eradicate disease inthe first instance, vaccination is now regarded as anappropriate strategy if initial efforts to eradicate the diseasevia slaughtering are not succeeding.

Disease costs

The UK FMD outbreak is estimated to have cost £3,800 million (US$5,186 million) (1). The 2003outbreak of avian influenza in the Netherlands cost at leastUS$612 million. Also in the Netherlands, the 1997-1998outbreak of classical swine fever cost US$2.52 billion.

The cost of disease is a complex issue. Direct costs thatmay arise for the producer include those that result from:

– loss of production

– culling of animals

– decline in overall consumption in the sector affectingoverall pricing both during a disease outbreak and forsome time afterwards

– future cost of promotion to stimulate demand

– cost of lobbying government.

Related sectors are impacted in various ways that mayinclude loss of feed sales, decline in the value of finishedproduct, scarcity of raw materials, loss of markets, etc.

Indirect costs can include:

– government subvention (vaccination programmes,culling, supervision of quarantine areas, compensation forculling, scientific facilities, negotiation of the lifting of salesbans with other countries, etc.)

– loss of tourism revenue (the FMD outbreak in the UKresulted in many areas of the country being placed offlimits to tourists)

– loss of overall employment, treatment of people whobecome ill.

It is clear, therefore, that major disease outbreaks entailsignificant costs to society. Consequently, the idea ofinvesting significantly in the prevention of disease makesvery good economic sense. In this context, many issuesneed to be considered, including:

a) the availability of vaccines to prevent a disease and theneed to invest in better vaccines

b) the availability of strategic reserves of vaccines and/orsera to respond to diseases that occur rarely (FMD)

c) the ability of industry to respond to a surge in demand(as was the case during the recent outbreak of avianinfluenza) and the need to stimulate production capacityby public intervention such as the regular purchase ofstrategic reserves.

In the context of avian influenza, the threat of a humanpandemic is of great concern. The Spanish flu killedbetween 20 million and 40 million people in 1918. TheAsian flu of 1957 killed between 1 million and 4 millionpeople, as did the 1968 Hong Kong flu. The ability to usebiosecurity, stamping out and vaccination to attempt toeliminate avian influenza and so possibly avoid a humanpandemic is of major societal importance and once againhighlights the value of vaccinating animals. Indeed, weneed to consider vaccine use on a global scale to stopdiseases at source and so prevent diseases becoming globalproblems.

Food safety and quality: the value of vaccines

The control of salmonella in the UK, as depicted in Figure 1, indicates the value of vaccination to society interms of public health. The elimination of FMD fromWestern Europe, as depicted in Figure 2, highlights the animal welfare value of vaccination. Similarly, from the


viewpoint of protecting health as opposed to treatingdisease, the decline in the use of antibiotics in Norwegiansalmon production after the introduction of appropriatevaccines, as depicted in Figure 3, further highlights thebenefits of vaccination.

Clearly, vaccination has a tremendous benefit directly tosociety, as well as to animal health and welfare. Thedesirability of using vaccines to minimise the threat ofother zoonoses to society is very clear: Escherichia coli,campylobacter, listeria, West Nile virus and Lyme diseaseare cases in point.

Animal testing

In developing vaccines, animal testing is needed at variousstages in order to assess safety and efficacy. Many of thetesting requirements are contained in the Europeanlegislative framework, as detailed in the EuropeanPharmacopoeia. Guidelines also exist clarifying whenanimal tests are required.

It is the wish of everybody concerned to minimise the useof animals in testing vaccines. In order to move forward,we need alternatives that are accepted across the globe. Itis of no value to introduce an alternative in one part of theglobe if other regions demand the animal-based test. The company is still forced to use the animal test if itwishes to continue to supply its product in the regiondemanding the test.

In this context, the International Cooperation onHarmonisation of Technical Requirements for theRegistration of Veterinary Products (VICH) has a key roleto play. VICH has the potential to harmonise regulatoryrequirements ensuring that the same test procedure isaccepted globally – this prevents duplication of testing. Inaddition, agreement may be reached where testing may bereplaced by alternatives not involving animals. Progressthrough this forum has the potential to deliver globalagreement on alternatives to animal testing.


*The Lion Quality Code of Practice, which was launched in 1998, includes independent

auditing, improved traceability, packing station hygiene controls, a ‘best-before’ date that is

earlier than that required by law and compulsory vaccination against Salmonella enteritidis.

Fig. 1

The incidence of human salmonellosis in England and Wales

(1981 to 2000)

Source: Advisory Committee on the Microbiological Safety of Food,

United Kingdom

Fig. 2

The elimination of foot and mouth disease from Western Europe

Mass vaccination was introduced in Western Europe in the mid 1960s

and was discontinued in 1992

Source: Intervet, Netherlands

Fig. 3

Norwegian salmon production, consumption of pure antibiotics

and the effect of vaccines

Source: Norwegian Ministry of Fisheries and Coastal Affairs, 2005

The initiative announced by the European Commission inNovember 2005 on alternatives to animal testing(European Partnership to Promote Alternative Approachesto Animal Testing [EPPAA]) is also important. Theobjective of the EPPAA is to replace, reduce or refine theuse of animals in testing (this strategy is referred to as the3 R’s initiative). It is important that we make every effort toreplace animal testing, and to this end the Commissionand industry from many sectors have combined to jointlywork on alternatives.

Over the years, progress has been made. For example,intra-cerebral safety testing in mice in relation to Aujeszky’sdisease vaccines has been eliminated.

Safety of food from vaccinated animals

A recently published EU study concerning the knowledgeof consumers in relation to avian influenza is of interest(2). Fifty-three per cent of the public believe that it isdangerous to eat the meat of a chicken vaccinated againstavian influenza. In the UK in 2001, the authorities did notuse vaccination to try to stop the spread of FMD as variousparties in the UK food chain indicated that they would nothandle produce from vaccinated animals. When oneexamines these two pieces of information together, theneed to communicate the safety of food from vaccinatedanimals becomes evident.

In a context where the public are concerned about thesafety of produce from vaccinated animals, the benefits ofvaccination, particularly in the context of a major diseaseoutbreak, may not be realisable. Most food animals receivea number of vaccinations during their life to protect themagainst various diseases and the public usually consumesuch produce without concern. It may be that they do notrealise that animals are vaccinated routinely or they may bemore cautious in the context of a disease outbreak that iswidely reported in the media and that may or may not havehuman health implications.

The challenge for both industry and government is tocommunicate information in a manner in which it will beaccepted by society at large and will assure the public thatproduce from vaccinated animals is safe to eat.

Future food needs

Figure 4 indicates the scale of the challenge facing globalagriculture if future food needs are to be satisfied. Aspreviously mentioned, animal diseases are responsible forat least a 17% loss in production, and theelimination/reduction of these losses must be a priority.

Meat consumption will increase by a factor of two indeveloped countries and by a factor of five in developing

countries. For milk, the factors are two and five,respectively. For eggs, the factors are three and eight,respectively. Herd health management will be key inattempting to meet this challenge and vaccination will havea central role to play.

As we move into the future, we anticipate, based onhistorical knowledge, that new diseases will emerge. Thisis all the more likely as farming intensifies in developingcountries and as a result, intensive agriculture comes intocontact with wild species. Our ability to be alert for suchdiseases and to have the scientific capacity andinfrastructure to respond to such challenges is critical. TheETPGAH recognises this reality. Amongst itsrecommendations is the need to ‘identify the threats toEurope from pathogens which are not consideredimportant at present (i.e. horizon scanning) and conductfull risk assessment of potential threats from new andemerging diseases in particular those outside the EUboundaries’ (3). Whilst reference is made to Europe, therecommendation is valid in any part of the globe.

The ETPGAH has also identified ‘societal acceptance oftechnology’ as an issue that needs attention. The StrategicResearch Agenda (SRA) from the ETPGAH proposesresearch into consumer perceptions and expectations ofnew technology and factors which affect consumerbehaviour in relation to food safety. The SRA also proposesthe development of risk communication strategies tocommunicate with the public in relation to newtechnology in the most effective manner. Part of this workshould be aimed at communicating the fact that food fromvaccinated animals is safe to eat.


Fig. 4

Predicted increase in the global consumption of livestock

products

Source: World Organisation for Animal Health

ConclusionThe development of vaccines is becoming more complexand expensive. The need to ensure the availability ofvaccines requires public and producer cooperation.Vaccines deliver considerable benefits to both animals andsociety at large and have the potential to deliver evengreater benefits in the context of the ETPGAH.

Mass slaughter must be avoided if possible and animalhealth needs to be protected to avoid the huge costsassociated with the outbreak of exotic diseases. Thedevelopment of a wider range of effective vaccines has thepotential to deliver benefits to society far in excess of thecost of development and this opportunity should not bemissed. Food safety and quality benefits flow from vaccineuse and we need to invest in alternatives to animal testing.

Future food needs at the global level highlight theimportant role and need for new and effective vaccines.The ETPGAH shows the way forward and thisdevelopment needs to be coupled with effectivecommunication with the public so that new vaccinetechnologies are accepted.

From the viewpoint of society, vaccination delivers veryconsiderable benefits. The human health benefits ofreducing zoonoses are very substantial and need to becommunicated in an effective manner. From the ethicalviewpoint, we need to protect animal health and welfare byusing vaccines to the greatest extent possible. In addition,we need to prove safety and efficacy whilst minimising theuse of animals in testing.


La vaccination animale et l’industrie pharmaceutique vétérinaire

D. O’Brien & S. Zanker

Résumé

Le marché des vaccins vétérinaires s’intéresse à de nombreuses espèces

animales mais reste limité en volume et il devient de plus en plus difficile et

onéreux de développer de nouveaux vaccins. Les vaccins sont l’un des moyens

les plus efficaces de prévenir la maladie chez les animaux comme chez l’homme.

Dans bien des cas, la vaccination a permis d’éliminer des maladies ou d’en

réduire l’impact sur la santé et le bien-être des animaux. La responsabilité

éthique impose de faire en sorte qu’un large éventail de vaccins soit disponible,

y compris lorsque le marché doit être soutenu financièrement comme c’est le

cas pour les espèces animales plus rares ou les pathologies moins fréquentes

désignées par l’acronyme MUMS (Minor Use and Minor Species). L’abattage

sanitaire massif étant devenu intolérable pour la société, nous devons évoluer,

dans la mesure du possible, vers des politiques de « vaccination pour la vie ».

Les vaccins nous permettent d’éviter le fardeau du coût de la maladie tout en

améliorant la sécurité sanitaire des aliments. Le développement des vaccins

devra se faire en recourant le moins possible à l’expérimentation animale. En

outre, il faudra faire en sorte que le public accepte la vaccination des animaux

destinés à la consommation, en tant que mesure destinée à protéger la santé et

le bien-être de tous les animaux. Dans une perspective d’avenir, grâce aux

vaccins nous serons en mesure d’assurer la sécurité alimentaire d’une

population mondiale de plus en plus nombreuse. La plateforme technologique

sur la santé animale dans le monde lancée par la Commission européenne a un

rôle déterminant à jouer pour fixer les priorités de la recherche.

Mots-clés

Bien-être animal – Démarche éthique – Maladie – Recherche – Santé – Sécurité

sanitaire des aliments – Vaccin vétérinaire.

References1. Anon. (2005). – Cost benefit analysis of foot and mouth

disease controls. A report for the Department forEnvironment, Food and Rural Affairs, United Kingdom. RiskSolutions. Available at: http://www.defra.gov.uk/animalh/diseases/fmd/pdf/costben.pdf (accessed on 8 May 2007).

2. European Commission (2006). – Special Eurobarometer 257.Avian Influenza. Directorate General for Health andConsumer Protection, Brussels. Available at: http://ec.europa.eu/public_opinion/archives/ebs/ebs_257_en.pdf (accessed on7 May 2007).

3. European Technology Platform for Global Animal Health(ETPGAH) (2006). – Prioritization of Animal Diseases.Stakeholder Meeting, 15 February, Brussels. Available at:http://www.ifahsec.org/2_CS_Disease%20prioritization.ppt(accessed on 7 May 2007).


Vacunación animal e industria farmacéutica veterinaria

D. O’Brien & S. Zanker

Resumen

Si bien el mercado de la inmunización veterinaria comprende la lucha contra las

infecciones que afectan a muchas especies animales, su talla es limitada y el

desarrollo de vacunas cada vez más complejo y oneroso. La vacunación, que es

uno de los instrumentos más eficaces para prevenir enfermedades tanto en los

animales, como en los seres humanos, ha permitido erradicar muchas

enfermedades, o reducir la gravedad de sus consecuencias en la salud y el

bienestar de los primeros. Desde el punto de vista ético, debe garantizarse la

existencia de una gran variedad de vacunas, aunque para ello sea preciso

prestar apoyo financiero al mercado, como en los casos de las especies

animales poco comunes y las indicaciones poco frecuentes (denominadas

habitualmente con la sigla MUMS, por las iniciales en inglés de “Minor Use and

Minor Species”). En la sociedad contemporánea, el rechazo del sacrificio

masivo es cada vez mayor; por ello, siempre que resulte posible debe adoptarse

una política de vacunación que impida la circulación de los agentes patógenos

en los rebaños. La inmunización es necesaria para evitar los elevados costos de

las enfermedades y garantizar la inocuidad de los alimentos. También es preciso

reducir al mínimo las pruebas en animales durante el desarrollo de vacunas. La

vacunación constituye un medio para proteger la salud y el bienestar de todos

los animales; por consiguiente, debe darse a comprender al público la necesidad

de administrarla a aquellos que se destinan al consumo. Las vacunas serán

indispensables para producir las cantidades de alimentos que serán necesarias

en el futuro a fin de alimentar a una población mundial cada vez más numerosa.

La Plataforma Tecnológica Europea para la Sanidad Animal Mundial

desempeñará un papel clave a la hora de determinar los ámbitos de

investigación prioritarios.

Palabras clave

Bienestar – Enfermedad – Ética – Inocuidad de los alimentos – Investigación – Salud –

Vacuna veterinaria.


The opinion of the production sector on

the role of vaccines in the control and eradication

of livestock diseases in Argentina

L. Miguens

Sociedad Rural Argentina, Florida 460, (1005) Ciudad Autónoma de Buenos Aires, Argentina.

E-mail: [email protected]

Summary

Research by a number of international organisations indicates that world

demand for red meat protein is set to increase significantly in the coming years.

However, faced with the risk of infectious animal diseases and zoonoses –

factors that could limit the growth of this production sector – the fight against

livestock diseases must continue, especially against those that affect food safety

or pose a threat to human life. The use of vaccination to prevent infectious

animal diseases is of key importance, not only because it helps to control and

effectively eradicate infectious livestock diseases, but also because it makes it

possible to introduce new technologies for intensive or semi-intensive

production, to protect the environment, to care for animal welfare and to

guarantee the safety of animal-derived foodstuffs.

As part of their professional culture, livestock producers have come to fully

appreciate the advantages of using vaccination to prevent disease rather than

curative measures, which are more costly to implement and in some cases not

very effective. The control of anthrax and rabies by means of effective vaccines

was a factor in the widespread development of livestock in Argentina and other

parts of Latin America. Recent results in the control and eradication of foot and

mouth disease have made producers even more convinced of the merits of this

technology.

Animal disease prevention has proven to be highly conducive to the production

of healthy foodstuffs. It is the responsibility of international organisations to draw

up appropriate regulations to protect trade, supply safe and healthy products

and prevent the application of unjustified non-tariff measures.

Keywords

Animal disease – Argentina – Control – Eradication – International trade – Livestock

producer – Vaccination – Vaccine.

Introduction

Cattle, which were introduced into America from Europeat the time of the Spanish conquest in the 15th Century,went on to breed easily in various regions of the Americas.Their numbers grew to unparalleled proportions in theRiver Plate region, which covers vast areas of Argentina,

Uruguay, Paraguay and southern Brazil. There was a hugenatural increase in the livestock population in theArgentine grasslands, especially during the 16th and 17thcenturies, so much so that by the early 18th Century theestimated population was similar to that of the present day(56 million head). Up until then no technologicalimprovements had yet been introduced into livestockproduction, which was 100% pastoral (4).

Livestock production was the main engine of the Argentineeconomy up until the mid-20th Century. Livestockproducers were able to play the key role in thisdevelopment thanks to new technology for geneticimprovement, the introduction of fencing, improvedanimal feeding techniques, the development andapplication of agrochemicals and fertilisers, the productionof modern farming machinery, and, finally, public sectorinitiatives to control livestock diseases, which receivedunstinting support from livestock organisations andproducers.

According to studies by specialised internationalorganisations, half of the world’s population earns less thantwo dollars per person per day (although one third of thispopulation, particularly in Asia and Latin America, is dueto increase its income significantly over the next twentyyears). What is more, 75% of the 1.2 billion or so peoplesubsisting on less than one dollar per day live and work inrural areas of developing countries (1). Although worlddemand for red meat protein is set to increase significantlyover the coming years, one of the main constraints onmeeting this demand will be the occurrence of infectiousanimal diseases and in particular zoonoses (3). Productionrates must therefore be increased and livestock diseasesreduced or eradicated, especially those affecting food safetyor posing a threat to human life. The prevention ofinfectious animal diseases by means of vaccination isparamount to safeguarding human life, not only because ithelps to control and effectively eradicate infectiouslivestock diseases, but also because it makes it possible tointroduce new technologies for intensive or semi-intensiveproduction, to protect the environment, to meet animalwelfare requirements and to guarantee the safety of animal-derived foodstuffs.

The livestock sector and the use of vaccinationThe livestock production sector in Argentina (and theRiver Plate region as a whole) has taken an active part inthe process of technology introduction to improveproduction conditions, especially health conditions, and inthe early 20th Century it began to use a number of toolsenabling it to overcome some serious health obstacles.

In the past fifty years, the production sector has groupeditself into local animal health committees (ComisionesLocales de Sanidad Animal) in every area of the country. Thecommittees work jointly with official veterinary sectorrepresentatives on schemes for the early diagnosis ofdiseases, especially foot and mouth disease, and formonitoring vaccination campaigns against foot and mouthand other livestock diseases. These local committees,

which are organised and operate much like animal healthgroups (Grupos de Defensa Sanitaria) in other countries,work in a coordinated manner at regional and nationallevel, facilitating the implementation of diseaseprogrammes.

The example of foot and mouth diseaseThe success achieved in controlling and eradicating footand mouth disease in Argentina in the 1990s and thespeedy control and eradication of subsequent events wereattributable to three key factors:

a) a realistic control and eradication plan

b) an excellent quality vaccine (safe, potent and pure)

c) the resolute and committed participation of productionsectors.

This convinced all stakeholders of the benefit of usingvaccination to control foot and mouth disease.

The first reports of foot and mouth disease in Argentinawere documented in 1890. The disease was present in thecountry up until the late 1980s and was endemicthroughout much of Argentina. Thereafter, the privatesector, working together with the health authorities, beganto take decisive action and to actively participate instrategic actions to control foot and mouth disease. Majorhealth changes began to be observed in affected regionscovered by the National Control and EradicationProgramme, with a drastic reduction in prevalence inaffected herds, showing that the programme was workingwell.

Bi-annual administration of the foot and mouth diseasevaccine with an oily adjuvant by the official VeterinaryServices, paid for by livestock producers, extended theprotection period and facilitated the effective surveillanceof all farms and herds (around 100% vaccine coverageagainst foot and mouth virus serotypes A, O and C formore than eight years).

Furthermore, the involvement of producers and producerorganisations guaranteed the continuity of programmeactivities and was one of the key factors in arresting andultimately eradicating the disease.

As part of their professional culture, livestock producershave come to fully appreciate the advantages of usingvaccination to prevent disease rather than curativemeasures, which are more costly to implement and insome cases not very effective. The control of anthrax and


rabies by means of highly effective vaccines facilitated thewidespread development of livestock in Argentina and therest of Latin America. Recent results in the control anderadication of foot and mouth disease have madeproducers even more convinced of the merits of thistechnology.

Throughout this process, livestock producers have alwaysrelied on the professional advice of veterinarians and of theofficial Veterinary Services. Indeed, this tripartiterelationship is the key to successfully implementing anydisease prevention action.

Modernisation of the sectorNowadays, increasing world demand for protein poses agreater challenge to livestock producers. They know thattheir production must satisfy basic environmentalconservation criteria, whilst world climate changedetermines the movement of their production to otherlatitudes, with different ecosystems, where there is agrowing threat of emerging and re-emerging infectiousanimal diseases (for the most part zoonoses). All thesefactors, coupled with greater demand for food safety, haveled producers to play a growing and committed role in theintroduction of new production technology.

Any economically sustainable development of livestockproduction, including access to international markets, istherefore inconceivable without the use of vaccines and ofeffective biosafety measures for the prevention, control anderadication of infectious livestock diseases. For this tohappen, international animal health regulations must takeinto account scientific advances in the field and reflect thestate of the art, bearing in mind that livestock producersare unconditional allies in animal health management andanimal production food safety.

However, these standards and recommendations mustclearly reflect the optimum use of vaccination technologiesin disease prevention and control, including theirlimitations, which in some cases may appearinsurmountable in the current state of knowledge. Oneexample is brucellosis control, where vaccination plansand the destruction of reactor animals are a necessary andeconomically valid prerequisite for definitively controllingand eradicating the disease, particularly among dairyherds.

Clearly, the use of stamping out measures to control anderadicate livestock diseases poses ethical andenvironmental problems. The recent episodes in Europe(foot and mouth disease in the United Kingdom and theNetherlands), Asia and Africa (avian influenza) havedemonstrated the serious limitations of stamping out

measures. The slaughter and destruction of thousands of‘healthy’ animals (2) and the subsequent environmentaldamage cause by the disposal of their remains (as in thecase of cattle during the bovine spongiformencephalopathy epidemic in Europe) elicited a profoundlynegative reaction among world public opinion.Fortunately, major changes have occurred in this area, suchas the Dutch Farmers’ Union proposal to use vaccination tocontrol the 2001 foot and mouth disease outbreak in theNetherlands.

These episodes also revealed that animal welfare conditionshad been severely undermined. However, livestockproducers are the first link in the chain for properimplementation of animal welfare practices: the animalsbelong to them – animals which they breed, select and carefor – and it is they who are ultimately responsible for whathappens to their animals.

The producers’ standpointArgentina’s livestock producers played an active andcommitted role in conjunction with the official veterinarysector in a successful ten-year programme for the controland eradication of foot and mouth disease, applyingpreventive vaccination to the entire cattle population inaccordance with the international standards andrecommendations of the World Organisation for AnimalHealth (OIE). In 2000, Argentina completed theeradication process and received international recognitionof its status by the OIE, proving, together with othercountries and regions in the Americas, that the routemapped out by the OIE was indeed feasible (5).

Fortunately, a number of important measures continued tobe taken after the disease was eradicated: the surveillanceand warning system was maintained, vaccine wasproduced on an industrial scale and an antigen/vaccinebank was set up. All this enabled Argentina to respondrapidly when foot and mouth disease recurred in theregion and to use emergency vaccination to bring thedisease under control in less than one year, leading to therecovery of Argentina’s foot and mouth disease status in2002. All these measures were taken without eliciting anegative response from the public, without affecting theenvironment by the mass destruction of animals and withno economic impact on livestock producers, who were ableto continue maintaining and increasing their herds incompliance with strict biosafety and animal welfarestandards. Argentina’s livestock producers are proud of thisachievement and believe it demonstrates their efficiency,something which would not have been possible withoutthe aid of a good preventive tool and an excellentvaccination programme. The investment in anantigen/vaccine bank has turned out to be amply justified


4. Ras N. (2001). – El origen de la riqueza en una fronteraganadera. Academia Nacional de Agronomía y Veterinaria,Buenos Aires, Argentina.

5. Secretaría de Agricultura, Ganadería y Pesca (1990). – Plan decontrol y erradicación de la fiebre aftosa en Argentina – Basespara el control de la fiebre aftosa. Secretaría de Agricultura,Ganadería y Pesca de la República Argentina, Buenos Aires.

References1. Díaz Bonilla E. & Gulati A. (2003). – Developing countries

and the WTO negotiations, trade policies and food security.The International Food Policy Research Institute,Washington, DC, United States of America.

2. Follet B. (ed.) (2002). – Infectious disease in livestock. TheRoyal Society Inquiry into Infectious Diseases in Livestock,chaired by Sir Brian Follet FRS. Perfect Page, London, UnitedKingdom.

3. Morgan N. & Prakash A. (2006). – International livestockmarkets and the impact of animal diseases. In Animalproduction food safety challenges in global markets (S.A.Slorach, ed.). Rev. sci. tech. Off. int. Epiz., 25 (2), 517-528.

economically, in view of the success in recovering marketsand production value. Other examples in other parts of theworld concerning other livestock diseases have yielded thesame results, to the great satisfaction of livestock producersin those countries.

ConclusionIn summary, it is livestock producers’ opinion that, overthe years, the use of vaccines has proven to be an excellenttechnological tool in preventing livestock diseases.

However, producers acknowledge that vaccines and theiruse should be subject to a series of basic requirements:

a) vaccines must comply with international regulations(OIE), which are considered to be minimum standards

b) vaccines must be safe and should not jeopardise foodsafety in any way. No discrimination must be madebetween products from vaccinated infection-free animalsand the same products from unvaccinated infection-freeanimals

c) vaccines used preventively should guarantee a longimmunity period, preferably for life. To achieve the desiredoutcomes, basic research on the subject will need to bepromoted and encouraged

d) vaccines should be stable and effective underenvironmental extremes of cold and heat

e) vaccines should be reasonably priced to enable their useeven in countries/regions with scarce economic resources.

Meeting growing world demand for foodstuffs, particularlyfrom the poorest countries, is acknowledged to be one ofthe responsibilities of livestock producers, together withother sectors. In economic terms, producers know how toproduce more and better products (healthier foodstuffs).

Based on their experience of controlling various epizootics,livestock producers will therefore continue to workactively with the official Veterinary Services and privateveterinarians to control and eradicate livestock diseases.

The need to guarantee healthy foodstuffs, in compliancewith new standards on animal production food safety, is achallenge for disease prevention programmes. Nowadayslivestock producers have two basic technologies at theirdisposal: biosafety and preventive vaccination. Biosafety,which can be implemented efficiently in integratedproduction systems, is very expensive to set up andmaintain, whereas preventive vaccination, which can beimplemented in all production systems, tends to becheaper. The recommendations of internationalorganisations must be followed in order to ensure theproper and efficient implementation of the two systemsand so facilitate market access for safe and healthyproducts. Clearly, these standards, which are based onleading-edge technology, do not introduce tariff measures.

The current vaccination strategy, which consists ofvaccinating the entire herd with an immunogen that isextremely pure as regards non-structural proteins, serves asa guarantee for hazard-free trade in animals and animalproducts from free countries practising vaccination to freecountries without vaccination.

Only if this type of strategy is used will vaccination be ableto play its role in the prevention, control and eradication oflivestock diseases.

AcknowledgementsThe author is grateful for the comments of DoctorsFederico Gonzalez Grey, Carlos van Gelderen andAlejandro Schudel, who revised this article.



ConclusionsFuture trends in veterinary vaccinology

As stated in the introduction to these two issues of the Scientific and Technical Review (the

Review) of the World Organisation for Animal Health (OIE), vaccination is without a doubt the

best means of preventing and, where possible, eliminating animal diseases. This is particularly

true for viral infections, if only because we do not have large-spectrum antivirals appropriate

for use in veterinary medicine. Vaccination can thus be considered an investment in animal

health insurance. Nonetheless, there are many unmet needs in animal health, and infections

for which there are as yet no vaccines.

Obstacles to the development of veterinary vaccines

Certain obstacles to the development of vaccines have already been cited in the introduction

to these two issues of the OIE Review; these difficulties, and others, are discussed in further

detail here.

Biological and technical obstacles

The first set of difficulties is biological and technical in nature. They account, for example, for

the scarcity of antiparasitic vaccines on the market. Parasites coexist with their hosts, and in

the course of their evolution have devised many strategies to maintain this coexistence.

This does not only apply to parasites, but also to viruses and bacteria. Viruses have co-evolved

with their hosts, and have also developed many strategies to survive, in relative state of

equilibrium, in a population or with a host. For example, they have acquired, often at

the expense of their host, many molecules or mechanisms that enable them to withstand the

various assaults of the immune response. This explains in part why, despite years of research,

there is as yet no vaccine available for African swine fever.

Moreover, many viral and bacterial infections, for example foot and mouth disease and avian

influenza, are caused by pathogens that have several serotypes and which constantly evolve.

A recent example of the problems brought about by serotypical variation is provided by the

appearance of bluetongue in Northern Europe due to serotype 8 (one amongst the 24 known

serotypes). Existing vaccines proved useless, as they did not contain the corresponding

antigens. However, for vector-borne diseases such as bluetongue, vaccination seems to be the

only solution. It is very difficult to attack the vector, especially through methods that have no

negative environmental impact.

Another difficulty inherent in veterinary vaccinology is the wide variety of target species, and

the number of different infections in each one. Vaccines, as opposed to therapeutic molecules

(antibiotics, anthelmintics), are for the most part extremely specific; there are only a few multi-

species vaccines containing the same antigenic valence (tetanus, rabies …).

Another problem for animal vaccination is that the target species include wildlife, which

are not always easy to access for the purpose of vaccination. For example it is not

possible to vaccinate vampire bats (Desmodus rotundus) in Latin America against rabies

because of the difficulty in gaining access to these animals. Other wild species, however,

such as foxes (Vulpes vulpes) (rabies) or wild boars (Sus scrofa) (classical swine fever) are

relatively easy to gain access to and can be vaccinated by means of vaccinal baits.

The appearance of new emerging diseases, for which, obviously, no vaccine exists at the

moment of emergence, presents another challenge for the development of animal

vaccines. One example of this is the Nipah virus infection that occurred in Malaysia: as

this was a lethal zoonosis, the only solution was the systematic slaughter of infected pigs

and the destruction or burial of their carcasses. However, in the United States of America,

the emergence of West Nile virus infection, which affects humans and a variety of

animals species, but principally horses, led to the development and marketing of eight

different equine vaccines in an exceptionally short space of time.

Similarly, the re-emergence of transboundary diseases in countries hitherto free of them

is another threat, the risk of which is heightened by growth in the ‘five T’s’ (Transport,

Travel, Tourism, Trade, Terrorism). These diseases generally originate in developing or

transition countries that lack the means to protect themselves; for the international

community, assisting the fight against these diseases where they occur, particularly

through vaccination, means protecting the entire planet. These diseases often have a

wildlife reservoir that is not easy to access, such as the African buffalo (Syncerus caffer)

for the SAT (South African Territories) strains of FMD.

Economic obstacles

Other obstacles to vaccination are of an economic nature. The most important one is the

low return on investment for private companies that develop veterinary vaccines for

livestock, especially for diseases specific to developing countries, which unfortunately is

where the needs are the greatest.

However, such problems are not confined to developing or transition countries, as certain

target species get little attention even in developed countries if they are considered

minor species. In Europe, for example, this is the case for milking sheep, goats, rabbits,

fish other than salmonids and fowl other than chicken. In addition, these minor species

are distributed unevenly over the different zones of Europe, which does not facilitate the

implementation of European-wide procedures for marketing veterinary vaccines. There is

also the problem of rare diseases both in the so-called major species (e.g. the European

form of malignant catarrhal fever in ruminants) and – the most catastrophic scenario – in

minor species (e.g. tularaemia in hares). This has led to the MUMS concept (Minor Use,

Minor Species). Developing vaccines for these types of diseases requires an equitable

public-private partnership.

Legal and regulatory obstacles

The last set of obstacles is legal and regulatory in nature. Many animal health regulations

favour hygienic prophylaxis and rule out preventive vaccination, especially in the

developed countries in which the major epizootics affecting domestic herds (foot and


mouth disease, classical swine fever) have been eliminated. Fortunately, there is a trend

toward the implementation of health policies that include vaccination (vaccination to live),

thanks in particular to the availability of new-generation vaccines which have a companion

diagnostic test and which contain a serological marker (DIVA technology: Differentiating

Infected and Vaccinated Animals). This availability has moved international organisations such

as the OIE to modify vaccination regulations.

Another regulatory obstacle to the development of veterinary vaccines for livestock is the

existence of very stringent and inflexible regulations governing the registration and marketing

of veterinary drugs (including vaccines). Such legislation does not promote flexibility in the

choice of vaccinal strains for vaccines capable of preventing infections caused by pathogens

with multiple serotypes, or in their adaptation to the epidemiological conditions in the field. In

addition, these very heavy regulations (which, however, present the considerable advantage of

guaranteeing quality and efficacy against the pathogen involved, as well as the safety of

commercial products) have recently been supplemented by additional regulations as a result of

environmental impact studies for veterinary drugs (certain anthelmintics for example). In this

respect, vaccines present a clear advantage over therapeutic molecules in that they do not

leave residues, and generally have no direct impact on non-target species (including

arthropods). Attenuated vaccines, however, require special attention, as they may become

dispersed amongst the target population or infect other, non-target species in their vicinity,

either in an agro-system or in an eco-system if the target species is a wildlife species.

Other obstacles

Public apprehension over vaccination or over certain products such as genetically modified

organisms may constitute a final obstacle. A specific case of this occurred during the recent

episode of FMD in the United Kingdom when it was found that consumers would have been

reluctant to consume products from vaccinated animals. This mistrust was one of the (minor)

reasons behind the decision not to resort to vaccination in attempting to control the disease

in 2001.

The current availability of DIVA-type vaccines against FMD, used in combination with

serological tests to detect antibodies against non-structural proteins (NSP) is, however, an

additional argument in favour of vaccination.

Veterinary vaccination: a complex issue

Veterinary vaccination is a particularly complex subject, due to the many factors that are

involved, such as the disparity of targets. As was said earlier, one of the main problems

encountered is the number of target species and the number of pathogens involved, as well as

their antigenic variation and the need to vaccinate several wildlife species that cannot be

easily accessed. The problem is compounded by the fact that the populations concerned are

not uniform: firstly, they are distributed across diverse geographical areas and secondly, within

each species the economic use to which animals are destined may differ. Although companion

animals and horses constitute relatively homogenous groups, this is not the case with

livestock, whose breeding conditions and intended use may vary enormously.

491Rev. sci. tech. Off. int. Epiz., 26 (2)

Different species present biological differences, in particular in terms of their immune

response modes and, more specifically, with regard to the transfer of maternal immunity from

mother to progeny. Whereas in primates this transfer is almost entirely transplacental, and

occurs during gestation, this is not the case with dogs and cats, in which a small portion of

passive immunity is transmitted during gestation, but most of which is transferred after birth.

Since these species are multiparous, there is a disparity in the quantity of immunoglobins

ingested by the different puppies or kittens of a given litter. In addition, there are quantitative

and qualitative differences between the immune statuses of different mothers, and a mother

can only transmit what she herself possesses. In perissodactyles and artiodactyles,

transmission occurs only after birth through the colostrum. In birds, this transmission occurs

via egg vitellus.

In addition to these fundamental biological differences that will influence vaccination

protocols, the intended use of the individuals within each species may vary enormously. Thus,

the lives of broilers are very different from those of laying hens; the same can be said for the

lives of young meat cattle and dairy cattle. Similarly, the use of breeders (bulls used for natural

or artificial insemination) differs from that of production animals. We could provide many more

examples. These differences bring about variations not only in the vaccination protocols to be

recommended, but also in the vaccines’ desired characteristics, in particular efficacy and

duration of protection. Laying hens live much longer than broilers, and dairy cattle live much

longer than cattle raised for slaughter. Moreover, within a given species there are clear

differences between breeds, e.g. the small dog breeds live longer than the large ones (one of

the major genes responsible for size in dogs has just been located). Owing to all these

differences, the desired length of vaccinal protection will vary. Dogs, cats and horses must be

protected throughout their biological life, which is long; broilers only require protection for the

few weeks of their short lives; laying hens should be protected for a year. Duration of

protection for wildlife species requires special attention, given population renewal rates and

life expectancy. For example, a survey has shown that the average life expectancy for foxes

(Vulpes vulpes) in continental Europe was no longer than three years. A vaccine against rabies

in foxes therefore need not confer longer protection.

Another decisive factor in veterinary vaccinology is the role played by the epidemiological and

pathogenic characteristics of an infection. These characteristics will have a great influence on

vaccination protocols. For example, vaccinating female cattle against the pestivirus

responsible for bovine viral diarrhoea/mucosal disease, in order to control the infection,

will aim at protecting the fetus during gestation, which will have a major impact on the

vaccination protocol.

New hope: future trends in veterinary vaccinology

Research and selective breeding

There has been much recent interest in unmet animal health needs on the part of several

international bodies, in particular the European Technology Platform for Global Animal Health

(ETPGAH) or, more recently, a joint European Union/United States Workshop on Advances in

Immunology and Vaccine Discovery. Their meetings have concluded that veterinary medical


research in immunology in domestic or wildlife target species should be intensified. To

this end, a list of international priority diseases has been drawn up. In particular,

immunological research into innate immunity in different species and means of

stimulating it should be pursued further; such research is facilitated by the fact that we

now have access to complete genome sequences for certain major species (chicken,

cattle, pigs, dogs …) and to methods for comparing them with those of other species

(man, mice). More concrete (vaccinological) research into adjuvants capable of

stimulating innate immunity is also a priority.

With regard to the major epizootic or enzootic diseases that we wish to eradicate, the

development of DIVA-type vaccines has provided us with a form of ‘soft’ disease control.

This is one of the most significant advances in animal health in recent years (this type of

vaccine has been used against Aujeszky’s disease and infectious bovine rhinotracheitis

among others).

Another important field for research in veterinary vaccinology is methods of vaccine

administration; this applies in particular to vaccines for wildlife or feral domestic animals.

These are receiving increasing attention since wildlife and feral domestic animals act as

a reservoir for identified diseases, but also for non-identified potential infections. Any

intervention in wildlife must take account of the need to protect biodiversity; indeed,

certain vaccinal interventions aim solely at the preservation of an endangered species

(conservation medicine).

The use of new biotechnologies and knowledge derived from the study of the genomics

of target species and their pathogens will undoubtedly help solve some of the problems

encountered in animal health. For example, there is a growing trend to orient livestock

selection not only toward production, but also toward animal health objectives by

selecting animals resistant to certain diseases. However, this approach appears

somewhat limited, as it is difficult to imagine a return to the production of more ‘rustic’

disease-resistant animals without losing the economic advantages of previous

selections. The example of resistance to Marek’s disease shows how difficult it is to

reconcile disease-resistance and productivity. Owing to the economic impact of this

disease on industrial poultry breeding, geneticists selected lines that were resistant to

the Marek’s disease virus, but in which certain characteristics that were positive from a

production point of view were unfortunately lost. As soon as an effective vaccine was

made available at an affordable price, breeders turned to vaccination, since they could

thus conserve the economic advantages of the previous selection.

Another approach could lie in the selection of animals that respond well to vaccination.

An analysis of the immune response in different dog breeds to rabies vaccination, in the

framework of the ‘pet scheme’ for the introduction of properly vaccinated animals into

the United Kingdom, showed considerable variation between breeds. Animal response to

vaccination is thus subject to great variability, a factor which could be used in the

selection, with or without markers, of good vaccination responders. It should, however,

be noted that there is a risk of encountering the same sort of unexpected results as when

selecting for resistance to specific diseases.


Sustainable solutions: flexible regulations and public/private partnership

Finally, it is to be hoped that regulations governing registration and marketing of vaccines

for livestock or wildlife will become more flexible, so that veterinary vaccines can meet

the epidemilogical requirements of field conditions, and that animal disease control

recommendations will take account of scientific and technological progress as well as of

the new vaccinal solutions available. In developing or transition countries, equitable

cooperation between the public and private sectors is advisable, in order to make

available high-quality, safe, effective and affordable products which can meet those

countries’ immense needs with regard to infectious tropical or parasitic diseases.

Whichever solutions are adopted, they must include provision for upholding animal

welfare and protecting public health and the environment, and not neglect the need to

maintain biodiversity and livestock sustainability over the long term. Although further

avenues for development are beginning to emerge, such as vaccines for therapeutic

rather than preventive purposes and anti-tumoral vaccination, it is too early to draw any

conclusions regarding this research.


Professor P.-P. Pastoret

Head of the Publications

Department

World Organisation

for Animal Health (OIE)

12 rue de Prony

75017 Paris

France

Email:

[email protected]

Dr A.A. Schudel

Vice-President of the Scientific

Commission

World Organisation

for Animal Health (OIE)

Urraca 1366, Carilo (7167)

Partido de Pinamar

Provincia de Buenos Aires

Argentina

Email:

[email protected]

Dr M. Lombard

Consultant in Biology

22 rue Crillon

69006 Lyons

France

Email:

[email protected]

Comme déjà mentionné dans l’introduction de ces deux numéros de la Revue scientifique

et technique de l’Organisation mondiale de la santé animale (OIE), la vaccination est sans

conteste la meilleure mesure pour prévenir les maladies infectieuses animales et

éventuellement les éliminer. Ceci est particulièrement vrai pour les infections d’origine

virale, notamment parce que nous ne possédons pas encore de molécules antivirales à

large spectre utilisables en médecine vétérinaire. La vaccination peut donc être

considérée comme un investissement visant à garantir la santé animale. Il existe

néanmoins de nombreux besoins en santé animale qui ne sont pas encore satisfaits et

des infections contre lesquelles il n’existe pas encore de vaccins.

Les obstacles au développement de vaccins vétérinaires

Les obstacles au développement de vaccins seront examinés en détail ci-après ; certains

d’entre eux ont déjà été mentionnés dans l’introduction de ces deux numéros

thématiques de la Revue.

Obstacles biologiques et techniques

Les premières difficultés sont d’ordre biologique et technique. Ceci permet, par exemple,

d’expliquer pourquoi il existe peu de vaccins antiparasitaires sur le marché. Les parasites

cohabitent en effet avec leur hôte et ont développé au cours de l’évolution de

nombreuses stratégies qui autorisent cette cohabitation.

Ceci n’est pas seulement vrai pour les parasites, mais vaut également pour les virus ou

les bactéries. Les virus ont co-évolué avec leur hôte et ont également développé de

nombreuses stratégies pour survivre dans une population ou chez leur hôte dans un

certain état d’équilibre. Ils ont notamment acquis, souvent aux dépens de leur hôte, de

nombreuses molécules ou des mécanismes qui leur permettent de circonvenir les

différents bras armés de la réponse immune. C’est ce qui explique, en partie, l’absence

de vaccin disponible contre la peste porcine africaine, malgré de nombreuses années

de recherche.

D’autre part, nombre d’infections virales et bactériennes sont provoquées par des agents

pathogènes possédant plusieurs sérotypes (comme la fièvre aphteuse et l’influenza

aviaire), et qui évoluent constamment. Un exemple récent des difficultés engendrées par

cette variation sérotypique est celui de la fièvre catarrhale ovine apparue dans le Nord

de l’Europe, qui était due au sérotype 8 (un parmi les 24 sérotypes connus). Les vaccins

existants étaient inutilisables car ils ne contenaient pas les antigènes correspondants.

Pourtant, pour des maladies vectorielles comme la fièvre catarrhale ovine, la vaccination


ConclusionsTendances futures de la vaccinologie vétérinaire

semble être la seule solution, car il est particulièrement difficile de s’attaquer au vecteur,

surtout si l’on souhaite recourir à des méthodes qui n’aient pas un impact négatif sur

l’environnement.

Une autre difficulté inhérente à la vaccinologie vétérinaire est la grande diversité des

espèces cibles et des infections affectant chacune d’entre elles. Les vaccins ont la

particularité, contrairement aux molécules thérapeutiques (antibiotiques,

anthelminthiques) d’être le plus souvent étroitement spécifiques ; il n’existe que peu de

vaccins multi-espèces comportant la même valence antigénique (tétanos, rage…).

Enfin, le fait que les cibles comptent nombre d’espèces sauvages, difficiles d’accès par la

vaccination, pose encore un autre problème. Par exemple, il paraît difficile de vacciner

contre la rage les chauves-souris vampires (Desmodus rotundus) en Amérique latine. En

revanche, d’autres espèces sauvages comme le renard (Vulpes vulpes) (dans le cas de la

rage) ou le sanglier (Sus scrofa) (dans le cas de la peste porcine classique) sont d’un

accès relativement aisé et peuvent être vaccinées facilement grâce à la méthode des

appâts vaccinaux.

L’apparition de nouvelles maladies émergentes pour lesquelles aucun vaccin n’existe au

moment de leur apparition représente un défi supplémentaire pour le développement des

vaccins vétérinaires. L’infection par le virus Nipah apparue en Malaisie en est un

exemple : comme il s’agissait d’une anthropozoonose mortelle, la seule solution a été

l’abattage systématique des porcs infectés et la destruction ou l’enfouissement de leurs

cadavres. En revanche, aux États-Unis d’Amerique, l’émergence de l’infection par le virus

de la fièvre du Nil occidental, qui affecte l’homme et nombre d’espèces animales, mais

particulièrement les chevaux, a conduit au développement et à la mise sur le marché de

huit vaccins équins différents dans un laps de temps exceptionnellement court.

De même, la réémergence de maladies transfrontalières dans certains pays auparavant

indemnes constitue une menace, dont le risque est augmenté par l’effet accru des

« cinq T » (Transport, Travel, Tourism, Trade, Terrorism : les transports, les déplacements,

le tourisme, le commerce et le terrorisme). Ces maladies proviennent généralement de

pays en développement ou en transition qui n’ont pas les moyens de s’en défendre ; pour

la communauté internationale, aider à combattre ces maladies là où elles sévissent,

notamment par la vaccination, c’est protéger l’ensemble de la planète. Ces maladies

possèdent souvent un réservoir sauvage difficilement accessible, comme le buffle

africain (Syncerus caffer) pour les souches SAT (South African Territories) de la fièvre

aphteuse.

Obstacles économiques

D’autres obstacles à la vaccination sont de nature économique : le premier d’entre eux

est le faible retour d’investissement que peuvent espérer les laboratoires privés

impliqués dans le développement de vaccins vétérinaires destinés aux animaux de rente,

particulièrement pour des maladies spécifiques des pays en développement, là où

malheureusement les besoins se font le plus sentir.

Ces problèmes, toutefois, ne se limitent pas aux pays en développement ou en transition

car, même dans les pays développés, certaines espèces cibles font l’objet de peu


d’attention lorsqu’elles sont jugées « mineures » ; par exemple, en Europe, sont qualifiés

d’espèces mineures les moutons producteurs de lait, les chèvres, les lapins, les poissons

autres que les salmonidés et les oiseaux autres que les poulets. À cela s’ajoute le fait

que ces espèces mineures sont diversement réparties dans les différentes zones de

l’espace européen, ce qui ne facilite pas la mise en œuvre de procédures européennes

pour la mise sur le marché des vaccins vétérinaires. S’ajoute encore l’existence de

maladies rares à la fois dans les espèces considérées comme majeures (par exemple la

forme européenne du coryza gangréneux chez les ruminants) et, scénario le plus

catastrophique, dans les espèces dites mineures (par exemple la tularémie du lièvre).

Ceci a conduit au concept désigné par l’acronyme MUMS (Minor Use, Minor Species

[utilisations mineures et espèces mineures]). Le développement de vaccins pour ces types

de maladies passe nécessairement par un partenariat public-privé équitable.

Obstacles juridiques et réglementaires

Les derniers obstacles sont de nature réglementaire et juridique. Nombre de

réglementations applicables à la santé animale privilégient la prophylaxie sanitaire et

excluent la vaccination préventive, particulièrement dans les pays développés qui ont

éliminé les grandes épizooties du cheptel domestique (fièvre aphteuse, peste porcine

classique). Heureusement, un changement se dessine en faveur de la mise en œuvre de

politiques incluant la vaccination (« vaccination-to-live », c’est-à-dire visant au maintien

en vie des animaux), notamment grâce à la disponibilité de vaccins de nouvelle

génération, associés à un test de diagnostic compagnon et pourvus d’un marqueur

sérologique (technologie DIVA permettant de différencier les animaux infectés des

animaux vaccinés). Cette possibilité a permis aux instances internationales telles que

l’OIE de modifier les normes applicables à la vaccination.

Un autre frein réglementaire au développement de vaccins vétérinaires pour les animaux

de rente est l’existence de réglementations très strictes et rigides pour l’enregistrement

des médicaments vétérinaires (y compris les vaccins) et leur mise sur le marché. Cette

législation ne favorise pas la flexibilité dans le choix des souches vaccinales pour la

composition de vaccins appropriés à la prévention des infections provoquées par des

agents pathogènes aux multiples sérotypes, et leur adaptation aux conditions

épidémiologiques du terrain. À cette réglementation très contraignante, mais qui a

cependant le grand mérite de garantir la qualité et l’efficacité vis-à-vis de l’agent

pathogène visé ainsi que la sécurité des produits commercialisés, se sont plus

récemment ajoutées de nouvelles exigences, rendues nécessaires par l’étude de l’impact

des médicaments vétérinaires sur l’environnement (c’est notamment le cas de certains

anthelminthiques).

À cet égard, les vaccins présentent un net avantage par rapport aux molécules

thérapeutiques car ils ne provoquent pas la formation de résidus et n’ont généralement

pas d’impact direct sur les espèces non cibles (arthropodes inclus). Une attention

particulière doit cependant être apportée aux vaccins atténués qui peuvent se disséminer

dans la population cible ou infecter d’autres espèces non cibles qui leur sont proches, que

ce soit dans un agro-système ou dans un écosystème s’il s’agit d’espèces sauvages.


Autres obstacles

Un dernier obstacle peut être constitué par la méfiance du public à l’égard de la

vaccination ou de certains produits comme les organismes génétiquement modifiés. Un

cas particulier a été la réticence du public à consommer des produits issus d’animaux qui

auraient été vaccinés contre la fièvre aphteuse lors du récent épisode de cette maladie

au Royaume-Uni. Cette méfiance a été l’une des raisons (mineure) qui ont motivé la

décision de ne pas utiliser la vaccination pour tenter de juguler l’épizootie en 2001.

La disponibilité actuelle de vaccins de type DIVA contre la fièvre aphteuse, qui s’utilisent

avec des tests sérologiques de détection des anticorps dirigés contre les protéines non

structurelles est désormais un argument supplémentaire en faveur de la vaccination.

La vaccination vétérinaire : une thématique complexe

La vaccination vétérinaire est une question particulièrement compliquée du fait des

nombreux facteurs qui interviennent, par exemple la disparité des cibles. Ainsi qu’il a été

mentionné auparavant, l’un des principaux problèmes rencontrés est le nombre

d’espèces cibles et le nombre de pathogènes impliqués, ainsi que leur variation

antigénique et le fait de devoir vacciner certaines espèces sauvages difficilement

accessibles. Le problème se complique du fait que les populations animales ne sont pas

uniformes : d’une part, leur répartition géographique est hétérogène et, d’autre part, une

même espèce peut faire l’objet de plusieurs types de production différents. Si les

animaux de compagnie et les chevaux constituent des groupes relativement homogènes,

il n’en va pas de même pour les animaux de rente dont l’utilisation économique et les

conditions d’élevage sont extrêmement diverses.

Les espèces diffèrent biologiquement entre elles, notamment dans leur mode de réponse

immune et, plus spécifiquement, dans le transfert de l’immunité maternelle de la mère à

sa descendance. Alors que chez les primates ce transfert se fait presque entièrement

durant la gestation par voie transplacentaire, il n’en va pas de même chez les chats et les

chiens, chez qui une faible partie de l’immunité passive est transmise durant la gestation,

la part la plus importante étant transmise après la naissance. Ces espèces étant

multipares, ceci crée une disparité dans la quantité d’immunoglobines ingérées par les

différents chiots ou chatons de la même portée ; à cela s’ajoutent les différences

quantitatives et qualitatives de l’état immun des mères : or une mère ne peut transmettre

que ce qu’elle possède elle-même. Chez les périssodactyles et les artiodactyles, la

transmission s’opère exclusivement après la mise-bas par le biais du colostrum. Chez les

oiseaux, cette transmission s’opère par le vitellus de l’œuf.

En plus de ces différences biologiques fondamentales qui vont influencer les protocoles

de vaccination, l’usage auquel sont destinés les individus d’une même espèce peut varier

considérablement. Ainsi, les conditions de vie des poulets de chair diffèrent de celles des

poules pondeuses ; celles des veaux de boucherie diffèrent de celles des vaches laitières.

De même, les animaux reproducteurs (taureaux utilisés pour l’insémination naturelle ou

artificielle) ne sont pas exploités de la même manière que les animaux producteurs. On


pourrait multiplier les exemples. Ces différences entraînent des variations non seulement

dans les protocoles de vaccination recommandés, mais également dans les

caractéristiques souhaitables des vaccins, notamment en termes d’efficacité et de durée

de protection. Les poules pondeuses vivent bien plus longtemps que les poulets de chair,

il en va de même des vaches laitières par rapport aux bovins de boucherie. De plus, au

sein d’une même espèce il existe de nettes différences entre les races ; ainsi les petites

races canines vivent plus longtemps que les grandes (l’un des principaux gènes

responsables de la taille chez le chien vient d’être localisé). Du fait de toutes ces

différences, la durée de protection attendue d’un vaccin est elle-même variable. Les

chiens, les chats, les chevaux doivent être protégés durant toute leur vie biologique, qui

est longue. Les poulets de chair ne doivent être protégés que pendant les quelques

semaines que dure leur vie ; les poules pondeuses doivent être protégées durant une

année entière. Une attention particulière doit être portée sur la durée de protection des

espèces sauvages, en tenant compte du renouvellement de la population et de son

espérance de vie. Une enquête a, par exemple, montré que la durée moyenne de vie des

renards (Vulpes vulpes) en Europe continentale n’excédait pas trois ans. Par conséquent,

la protection conférée par un vaccin antirabique destiné au renard peut ne pas dépasser

cette période.

Un autre facteur déterminant en vaccinologie vétérinaire est le rôle joué par les

caractéristiques épidémiologiques et pathogéniques d’une infection, qui vont influencer

de manière déterminante les protocoles de vaccination. Par exemple, la vaccination des

vaches pour contrôler l’infection due au Pestivirus responsable de la diarrhée virale

bovine/maladie des muqueuses, aura pour but de protéger le fœtus durant la gestation,

ce qui aura un impact majeur sur le protocole de vaccination.

Un nouvel espoir : les tendances futures de la vaccinologie vétérinaire

La recherche et l’élevage sélectif

Plusieurs instances internationales se sont récemment penchées sur les besoins non

satisfaits en santé animale ; c’est en particulier le cas de la Plateforme technologique

européenne sur la santé animale dans le monde (ETPGAH), ou plus récemment de

l’Atelier conjoint États-Unis d’Amérique/Union européenne sur les avancées en matière

d’immunologie et les découvertes en vaccinologie. Il ressort de ces rencontres que la

recherche en médecine vétérinaire consacrée à l’immunologie des espèces domestiques

ou sauvages doit être intensifiée. Une liste de maladies prioritaires au niveau mondial a

également été établie. Il convient notamment d’approfondir la recherche sur l’immunité

innée des différentes espèces et sur les moyens de la stimuler ; cette approche est

actuellement facilitée par le fait que les séquences génomiques complètes de certaines

espèces majeures (poulet, bovins, porc, chien…) sont désormais connues et que des

approches comparatives relatives au génome d’autres espèces (homme, souris) sont

disponibles. La recherche d’adjuvants capables de stimuler l’immunité innée figure

également parmi les priorités des applications concrètes de la vaccinologie.



Pour ce qui est des grandes épizooties ou des maladies enzootiques dont on souhaite

l’élimination, le développement de vaccins de type DIVA a apporté une solution qui

autorise une méthode « douce » de contrôle. Il s’agit là d’une des avancées les plus

remarquables en santé animale ces dernières années (ce type de vaccin a été utilisé avec

succès contre la maladie d’Aujeszky et la rhinotrachéite infectieuse bovine, parmi

d’autres).

Un autre grand chantier de la vaccinologie vétérinaire est celui du mode d’administration

des vaccins ; ceci vaut en particulier pour les vaccins destinés à la faune sauvage ou aux

espèces domestiques errantes. On y porte de plus en plus d’attention car ces animaux

jouent souvent un rôle de réservoir pour des infections connues, mais aussi pour des

infections potentielles non encore identifiées. Toute intervention sur la faune sauvage

doit prendre en compte le souci du maintien de la biodiversité, certaines interventions

vaccinales ayant d’ailleurs pour seul but la conservation d’une espèce menacée


L’utilisation des nouvelles biotechnologies et des connaissances dérivées de la

génomique des espèces cibles et de leurs pathogènes aidera certainement à résoudre

certains problèmes rencontrés en santé animale. Par exemple, une tendance actuelle

consiste à orienter la sélection des animaux de rente non plus seulement vers des

objectifs de production, mais aussi vers des objectifs sanitaires en sélectionnant des

animaux résistants vis-à-vis de certaines maladies. Toutefois, cette approche présente

certaines limites, car il paraît difficile de revenir à une production d’animaux plus

« rustiques » et résistants aux maladies sans perdre les acquis économiques des

sélections antérieures. L’exemple de la résistance à la maladie de Marek est là pour nous

rappeler la difficulté à concilier la résistance aux maladies avec les impératifs de

productivité. Du fait de l’impact économique de cette maladie sur l’élevage industriel des

volailles, des généticiens avaient sélectionné des lignées résistantes au virus de la

maladie de Marek, en perdant malheureusement certains traits de production

intéressants. Dès qu’un vaccin efficace fut disponible à un prix abordable, les éleveurs

ont privilégié la vaccination, car elle permettait de conserver les acquis économiques de

la sélection antérieure.

Une autre voie d’approche serait la sélection d’animaux bons répondeurs à la vaccination.

Une analyse de la réponse immune des différentes races de chien à la vaccination

antirabique dans le cadre du programme d’introduction d’animaux dûment vaccinés au

Royaume-Uni (pet scheme) a révélé une variation considérable entre les races à l’égard

de cette vaccination. Il existe donc une variabilité importante dans la réponse des

animaux à la vaccination, qui pourrait être mise à profit dans la sélection, assistée ou non

de marqueurs, d’animaux bons répondeurs. Il faut cependant remarquer que l’on risque

de rencontrer le même type d’aléas que celui rencontré lors de la sélection de traits de

résistance vis-à-vis de maladies spécifiques.

Des solutions durables : une réglementation plus souple et des partenariats public/privé

Enfin, il faut souhaiter que la réglementation en matière d’enregistrement et

d’autorisation de mise sur le marché des vaccins destinés aux animaux de rente ou

sauvages s’assouplisse, afin de permettre aux vaccins vétérinaires de satisfaire aux

besoins épidémiologiques du terrain, et que les prescriptions zoosanitaires pour le

contrôle des maladies tiennent compte des avancées scientifiques et technologiques

ainsi que des nouvelles solutions vaccinales disponibles. Pour ce qui est des pays en

développement ou en transition, il faut espérer qu’une coopération équitable entre le

secteur privé ou public s’établisse afin de rendre disponibles des produits de qualité,

efficaces et sûrs, économiquement abordables, qui permettent de satisfaire les

immenses besoins de ces pays confrontés aux maladies tropicales infectieuses ou

parasitaires. Quelles que soient les solutions apportées, elles doivent prendre en compte

la bientraitance animale, la protection de la santé publique, la protection de

l’environnement et le nécessaire maintien de la biodiversité et de la durabilité de

l’élevage à long terme. D’autres secteurs de développement commencent à être

identifiés : il s’agit des vaccins à visée thérapeutique plutôt que préventive et de la

vaccination antitumorale ; il est cependant trop tôt pour en dresser un quelconque bilan

aujourd’hui.

Professeur P.-P. Pastoret

Chef du Service des

publications

Organisation mondiale de la

santé animale (OIE)

12 rue de Prony

75017 Paris

France

e-mail : [email protected]

Dr A.A. Schudel

Vice-Président de la

Commission scientifique de

l’Organisation mondiale de la

santé animale (OIE)

Urraca 1366

Carilo (7167)

Partido de Pinamar


Argentine

e-mail :

[email protected]

Dr M. Lombard

Consultant en biologie

22 rue Crillon

69006 Lyon

France

e-mail :

[email protected]


Como queda dicho en la introducción a estos dos números de la Revista científica

y técnica de la Organización Mundial de Sanidad Animal (OIE), la vacunación es,

incontestablemente, la medida más eficaz para prevenir y eventualmente eliminar las

enfermedades infecciosas de los animales, en especial las infecciones de origen vírico,

sobre todo porque aún no disponemos de moléculas antivirales de amplio espectro que

puedan utilizarse en medicina veterinaria. Desde este punto de vista, cabe equiparar la

vacunación a invertir en un seguro de enfermedad animal. Sin embargo, hay numerosas

necesidades todavía desatendidas en materia de sanidad animal, así como infecciones

contra las que no existe ninguna vacuna.

Los obstáculos a la obtención de vacunas veterinarias

Algunos de los obstáculos que dificultan la obtención de vacunas vienen ya mencionados

en la introducción a estos dos números temáticos de la Revista de la OIE. Estos

obstáculos y otros serán discutidos en mayor detalle a continuación.

Obstáculos biológicos y técnicos

Las primeras dificultades son de orden biológico y técnico, y permiten explicar, por

ejemplo, por qué hay tan pocas vacunas antiparasitarias disponibles en el mercado. Los

parásitos, en efecto, conviven con el hospedador, y en el curso de la evolución han ido

desarrollando numerosas estrategias para adaptarse a esa situación.

Ello se aplica no sólo a los parásitos, sino también a los virus y bacterias. Los virus han

coevolucionado con sus hospedadores, y generado asimismo muchas estrategias para

sobrevivir en un cierto estado de equilibrio dentro de una población o un organismo

hospedador. Sobre todo han adquirido, a menudo a costa del hospedador, numerosas

moléculas o mecanismos que les permiten eludir los diversos brazos armados de la

respuesta inmunitaria. Esto explica, en parte, que tras muchos años de investigación, aún

no dispongamos de una vacuna contra la peste porcina africana.

Por otro lado, muchas infecciones víricas y bacterianas son causadas por agentes

patógenos que poseen múltiples serotipos, sujetos además a constante evolución, como

es el caso de la fiebre aftosa o la influenza aviar. La reciente aparición en el Norte de

Europa de la fiebre catarral ovina causada por el serotipo 8 (uno de los 24 que se conocen)

brinda buen ejemplo de las dificultades que puede acarrear semejante variabilidad

serotípica. Las vacunas existentes eran inutilizables porque carecían de los

correspondientes antígenos. Y sin embargo, en el caso de enfermedades vectoriales

como la fiebre catarral ovina, la única solución parece radicar en las vacunaciones, pues

resulta especialmente difícil atacar al vector, sobre todo con métodos que no dañen el

medio ambiente.


ConclusionesTendencias de la vacunología veterinaria en el futuro

Otra de las dificultades inherentes a la vacunología veterinaria estriba en la gran

variedad de especies destinatarias y las numerosas infecciones distintas que pueden

afectar a cada una de ellas. Ahora bien, las vacunas, a diferencia de las moléculas

terapéuticas (antibióticos, antihelmínticos, etc.), tienen la particularidad de ser casi

siempre muy específicas; hay pocas vacunas multiespecíficas que presenten la misma

valencia antigénica (tétanos, rabia…).

Otro problema relativo a la vacunación de los animales es que entre las especies

destinatarias hay animales salvajes a los que es difícil llegar para administrarles una

vacuna. Buen ejemplo en este sentido es la dificultad de vacunar contra la rabia a los

murciélagos vampiro (Desmodus rotundus) de América Latina. Hay otras especies

salvajes, en cambio, como el zorro (Vulpes vulpes) (rabia) o el jabalí (Sus scrofa) (peste

porcina clásica), que son de un acceso relativamente fácil y se les puede administrar

vacunas empleando cebos vacunales.

La aparición de nuevas enfermedades emergentes, contra las cuales, naturalmente, no

hay vacuna alguna en el momento en el que aparecen constituye un desafío adicional

para el desarrollo de vacunas veterinarias. Tal fue el caso de la infección por el virus

Nipah surgida en Malasia: como además se trataba de una antropozoonosis mortal, la

única solución posible fue el sacrificio sistemático de los cerdos infectados y la

destrucción o inhumación de los cadáveres. Sin embargo, en los Estados Unidos de

América, la emergencia de la infección del virus de la fiebre del Nilo Occidental, que

afecta a los hombres y a varias especies animales, principalmente a los equinos, ha

llevado a elaborar y comercializar ocho vacunas equinas distintas en un lapso de tiempo

excepcionalmente corto.

Una amenaza similar proviene de la reaparición de enfermedades transfronterizas en

determinados países hasta entonces indemnes, cuyo nivel de riesgo aumenta a medida

que se intensifican los factores conocidos como los “cinco T” (Transport, Travel, Tourism,

Trade, Terrorism: transporte, viaje, turismo, comercio, terrorismo).

Estas enfermedades proceden generalmente de países en desarrollo o en transición que

no tienen medios para defenderse de ellas. Para la comunidad internacional, ayudar a

combatirlas allí donde atacan, sobre todo mediante la vacunación, equivale a ayudar al

planeta entero. Además, suelen poseer un reservorio salvaje al que es difícil acceder,

como ocurre con el búfalo africano (Syncerus caffer), reservorio de las cepas SAT (South

African Territories) de la fiebre aftosa.

Obstáculos económicos

Otros obstáculos a la vacunación son de índole económica, y el principal es la escasa

rentabilidad que las empresas privadas del sector pueden esperar obtener de la

elaboración de vacunas veterinarias para los animales de granja, sobre todo en el caso

de enfermedades específicas de los países en desarrollo, que por desgracia son

justamente los más necesitados en la materia.

Estos problemas, sin embargo, no afectan sólo a los países en desarrollo o en transición,

ya que incluso en los países desarrollados hay ciertas especies que reciben poca

atención y son consideradas “menores”. En Europa, por ejemplo, se califican de tales la

oveja productora de leche, la cabra, el conejo, todos los peces salvo los salmónidos y


todas las aves menos el pollo. Por si fuera poco, esas especies están repartidas de forma

heterogénea en las distintas zonas del espacio europeo, cosa que no ayuda a instituir

mecanismos de dimensión europea para comercializar vacunas veterinarias. La situación

se agrava además por la existencia de enfermedades raras a la vez en especies

consideradas “mayores” (por ejemplo la forma europea de fiebre catarral maligna en

rumiantes) y en especies llamadas “menores” (la peor combinación posible) (por ejemplo,

la tularemia en la liebre). De ahí que se haya acuñado el concepto de especie MUMS

(Minor Use, Minor Species: “usos menores y especies menores”). El desarrollo de

vacunas para enfermedades de este tipo pasa obligatoriamente por una alianza

equilibrada entre los sectores público y privado.

Obstáculos jurídicos y normativos

Los últimos obstáculos son de carácter normativo y jurídico. Muchos reglamentos

zoosanitarios privilegian la profilaxis higiénica con exclusión de la vacunación preventiva,

sobre todo en los países desarrollados que ya han logrado eliminar las grandes epizootias

de los animales domésticos (fiebre aftosa o peste porcina clásica). Afortunadamente,

empieza a perfilarse un cambio de rumbo en favor de la aplicación de políticas sanitarias

que incorporen la vacunación (vaccination to live), gracias sobre todo a la existencia de

vacunas de nueva generación que tienen una prueba de diagnóstico complementaria y

que están provistas de un marcador serológico (tecnología DIVA: diferenciar a los

animales infectados de los animales vacunados), lo que ha permitido a instancias

internacionales como la OIE modificar las normas relativas a la vacunación.

Otro factor jurídico que dificulta la obtención de vacunas veterinarias destinadas a los

animales de granja es la existencia de reglamentos muy estrictos y rígidos para registrar

y comercializar medicamentos veterinarios (incluidas las vacunas); esta legislación no

favorece la flexibilidad a la hora de elegir cepas que sirvan para crear vacunas adecuadas

para prevenir infecciones debidas a patógenos con múltiples serotipos y para adaptar

esas vacunas a las condiciones epidemiológicas reinantes sobre el terreno. Esta

aparatosa reglamentación, que sin embargo presenta la gran ventaja de garantizar la

calidad, la eficacia para el patógeno en cuestión y la seguridad de los productos

comercializados, ha sido reforzada últimamente por normas adicionales, fruto de los

estudios de impacto ambiental de los medicamentos (ciertos antihelmínticos, por

ejemplo). En este terreno las vacunas presentan una neta ventaja con respecto a las

moléculas terapéuticas, ya que no inducen la formación de residuos ni suelen tener

efectos directos sobre las especies no destinatarias (comprendidos los artrópodos). Pese

a ello, conviene prestar especial atención a las vacunas atenuadas que pueden

extenderse dentro de la población destinataria o infectar a otras especies afines, ya sea

en un “agrosistema” o en un “ecosistema” (cuando se trata de vacunar a una especie

salvaje).

Otros obstáculos

Un último obstáculo puede provenir de los recelos que alimenta el gran público respecto

a la vacunación o a ciertos productos como los organismos genéticamente modificados.

Un caso particular, en este sentido, fue el de la reticencia a consumir productos


procedentes de animales que hubieran sido vacunados contra la fiebre aftosa durante el

episodio infeccioso surgido hace pocos años en el Reino Unido. Esa desconfianza fue uno

de los factores (de importancia menor) que en 2001 motivaron la decisión de no utilizar

las vacunaciones para tratar de atajar la epizootia.

Ahora bien, la actual existencia de vacunas de tipo DIVA contra la fiebre aftosa, que se

usan con pruebas serológicas para detectar anticuerpos contra proteínas no estructurales

(NSP), constituye un argumento suplementario en favor de la vacunación.

La vacunación veterinaria: un tema complicado

Los numerosos factores que entran en juego, por ejemplo la disparidad de especies

destinatarias, hacen de la vacunación veterinaria un asunto especialmente complejo.

Como queda dicho, uno de los principales problemas reside en la intervención de un gran

número de especies y de patógenos, en la variabilidad antigénica de éstos y en la

necesidad de vacunar a ciertas especies salvajes a las que es difícil acceder.

El asunto se complica aún más por la falta de uniformidad entre las poblaciones: por un

lado su distribución geográfica es heterogénea, y por el otro las distintas poblaciones de

una especie pueden destinarse a usos económicos muy diversos. Los animales de

compañía y los caballos forman grupos relativamente homogéneos, a diferencia de los

animales de granja, cuyas condiciones de cría y utilización pueden ser muy variables.

Las especies son distintas biológicamente, en especial en su modo de respuesta

inmunitaria, y más específicamente en el modo de transferencia de la inmunidad materna

a la progenie. En los primates el proceso tiene lugar casi totalmente por vía placentaria

durante la gestación. En los gatos y perros, en cambio, se transmite por dicha vía sólo

una pequeña parte de la inmunidad pasiva, mientras que la parte más importante se

adquiere después del nacimiento. Así, al tratarse de especies multíparas, los cachorros

de una misma camada habrán ingerido una cantidad de inmunoglobulinas distinta en

cada caso. A ello se añaden diferencias cuantitativas y cualitativas en el estado

inmunitario de la madre, pues ésta sólo puede transmitir lo que ella misma posee. En los

perisodáctilos y artiodáctilos, la transmisión se realiza exclusivamente después del parto

a través del calostro. En las aves tiene lugar a través del vitelo del huevo.

Además de estas diferencias biológicas fundamentales, que van a influir en gran medida

en los protocolos de vacunación, dentro de cada especie también pueden variar

sobremanera los usos a los que vayan a destinarse los distintos individuos. Así, por

ejemplo, la vida de los pollos de engorde es completamente distinta a la de las gallinas

ponedoras, y la de un joven bovino de una raza de producción cárnica tiene poco que ver

con la de una vaca lechera. Los ejemplares reproductores (toros en inseminación natural

o artificial) son destinados a un uso muy distinto al de los animales productores. Cabría

ofrecer aún multitud de ejemplos en este sentido. Estas diferencias entrañan variaciones

no sólo en los protocolos de vacunación recomendados, sino también en las

características que deben revestir las vacunas, sobre todo en cuanto a su eficacia y a la

duración de la protección que confieren. Una gallina ponedora vive mucho más tiempo

que un pollo de engorde, una vaca lechera mucho más que sus congéneres destinados


directamente a la carnicería. Además, dentro de una misma especie hay marcadas

diferencias entre las razas: los perros de raza pequeña, por ejemplo, viven mucho más

tiempo que los de raza grande (se acaba de localizar uno de los principales genes que

determinan el tamaño de un perro). En función de todas estas diferencias variará la

duración prevista de la protección que ofrezca una vacuna. Los perros, gatos y caballos

requieren protección durante toda su vida biológica, que suele ser larga. En el caso de los

pollos de engorde, en cambio, sólo hay que protegerlos las pocas semanas que dura su

vida, mientras que las gallinas ponedoras deben ser protegidas durante un año. Especial

atención conviene prestar al intervalo de protección en las especies salvajes, teniendo

en cuenta la renovación de la población y la esperanza de vida de los individuos. Una

investigación demostró, por ejemplo, que en Europa continental los zorros (Vulpes vulpes)

no viven en promedio más de tres años. Por ello una vacuna antirrábica destinada al zorro

no debe necesariamente conferir protección durante un lapso de tiempo superior.

Otro factor clave para la vacunología veterinaria son las características epidemiológicas

y patogénicas de una infección, que van a influir decisivamente en los protocolos de

vacunación. Por ejemplo: la vacunación de hembras de bovino contra el Pestivirus

responsable de la diarrea viral bovina (o enfermedad de las mucosas), utilizada para

controlar la infección, tiene por finalidad proteger al feto durante la gestación, cosa que

determina el protocolo de vacunación.

Una nueva esperanza: tendencias de la vacunología veterinaria en el futuro

Investigación y cría selectiva

En los últimos años ha habido varias instancias internacionales que han trabajado sobre

las lagunas existentes en el terreno de la sanidad animal. Entre ellas destacan la

Plataforma Tecnológica Europea para la Sanidad Animal Mundial (ETPGAH) o, más

recientemente, un grupo de trabajo mixto de los Estados Unidos de América y la Unión

Europea que se ocupa de los avances en materia de inmunología y del descubrimiento de

vacunas. De las reuniones de esos foros de estudio se desprende que es indispensable

intensificar la investigación sobre la inmunología de las especies de las que se ocupa la

medicina veterinaria, tanto domésticas como salvajes. Se ha elaborado asimismo una

lista de enfermedades prioritarias a escala mundial. Desde el punto de vista de la

inmunología, es preciso proseguir las investigaciones sobre inmunidad innata en las

distintas especies y sobre posibles formas de estimularla, trabajo que hoy en día se ve

facilitado por el conocimiento de la secuencia genómica completa de algunas de las

especies más importantes (pollo, bovinos, cerdo, perro, etc.) y por los métodos

comparativos en relación con la de otras especies (hombre, ratón). Más concretamente

(en vacunología), la búsqueda de adyuvantes capaces de estimular la inmunidad innata

figura también entre las prioridades.

Por lo que respecta a las grandes epizootias o las enfermedades enzoóticas que

aspiramos a eliminar, la obtención de vacunas de tipo DIVA ha aportado una solución que

permite controlarlas con métodos poco agresivos. Se trata de uno de los avances más


notables de los últimos años en el terreno de la sanidad animal (este tipo de vacunas han

sido utilizadas exitosamente contra la enfermedad de Aujeszky y la rinotraqueítis

infecciosa bovina, entre otras enfermedades).

Otra de las grandes líneas de trabajo de la vacunología veterinaria gira en torno al modo

de administración de las vacunas, sobre todo en el caso de las vacunas destinadas a la

fauna salvaje o a ejemplares cimarrones de especies domésticas. Este tema viene

mereciendo una atención creciente, ya que estos animales cumplen a menudo una

función de reservorio de infecciones, tanto conocidas como aún no descritas pero

potencialmente peligrosas. Toda actuación que afecte a la fauna salvaje debe integrar la

voluntad de preservar la diversidad biológica. Tanto es así que ciertas intervenciones

vacunales tienen por objetivo único la protección de una especie amenazada


El uso de las nuevas tecnologías y del conocimiento obtenido con la genómica de las

especies destinatarias y sus patógenos ayudará sin duda a resolver algunos de los

problemas que tiene planteados la sanidad animal. Por ejemplo, una tendencia actual

que se viene afianzando es la de orientar la selección de los animales de granja hacia el

cumplimiento no sólo de objetivos de producción, como era el caso hasta ahora, sino

también de objetivos zoosanitarios mediante la selección de animales resistentes a

ciertas enfermedades. Sin embargo, esta línea de trabajo parece un tanto limitada, pues

cuesta imaginar un retorno a la producción de animales más “rústicos” y resistentes a

enfermedades sin sacrificar por el camino las ventajas económicas logradas con

anteriores selecciones. El ejemplo de la enfermedad de Marek es un buen recordatorio

de la dificultad de conciliar la resistencia a las enfermedades con la productividad. En

vista de las grandes pérdidas económicas que la enfermedad de Marek infligía a la

industria avícola, una serie de genetistas había seleccionado linajes resistentes al virus

responsable de esa dolencia, pero ello, lamentablemente, supuso la pérdida de ciertos

rasgos de producción interesantes. En cuanto se obtuvo una vacuna eficaz y de precio

asequible para los productores, éstos empezaron a privilegiar la vacunación, que les

permitía conservar la rentabilidad económica obtenida con la selección anterior.

Otro posible ángulo de trabajo consistiría en seleccionar animales que respondieran bien

a la vacunación. El análisis de la respuesta inmunitaria que distintas razas de perro

ofrecieron a la vacunación antirrábica, como parte del “pet scheme” para introducir

animales correctamente vacunados en el Reino Unido, puso de relieve sobre todo una

considerable variación entre razas. Así pues, hay un nivel importante de variabilidad en

la respuesta de los animales a una vacuna, factor que podría utilizarse para seleccionar,

con o sin ayuda de marcadores, animales que ofrecieran una buena respuesta a la

vacunación. Conviene señalar sin embargo que quizá tropecemos con el mismo tipo de

imponderables que los surgidos en los procesos de selección con respecto a

enfermedades específicas.

Soluciones sostenibles: reglamentaciones más flexibles yasociaciones entre sectores público y privado

Es deseable, por último, que la reglamentación en materia de registro y comercialización

de vacunas para animales salvajes o de granja presente mayor flexibilidad, de manera

que las vacunas puedan responder a las necesidades epidemiológicas que surjan sobre


Profesor P.-P. Pastoret

Jefe del Servicio de

Publicaciones

Organización Mundial de

Sanidad Animal (OIE)

12 rue de Prony

75017 París

Francia

e-mail: [email protected]

Dr. A.A. Schudel

Vicepresidente de la Comisión

Científica de la Organización

Mundial de Sanidad Animal

(OIE)

Urraca 1366

Carilo (7167)

Partido de Pinamar


Argentina

e-mail:

[email protected]

Dr. M. Lombard

Consultor en biología

22 rue Crillon

69006 Lyon

Francia

e-mail:

[email protected]


el terreno, y que las prescripciones zoosanitarias para el control de enfermedades tengan

en cuenta los adelantos científicos y tecnológicos, así como la aparición de nuevas

soluciones basadas en el uso de vacunas. Por lo que respecta a los países en desarrollo

o en transición, cabe esperar que en ellos empiecen a establecerse mecanismos

equitativos de colaboración entre los sectores público y privado para comercializar

productos de calidad, eficaces, seguros y de precio asequible, que permitan satisfacer las

inmensas necesidades de dichos países en materia de enfermedades tropicales

infecciosas o parasitarias. Sean cuales sean las soluciones que se ofrezcan, éstas

deberán integrar debidamente planteamientos como el bienestar de los animales, la

protección de la salud pública o la protección del medio ambiente, sin olvidar el

indispensable mantenimiento de la diversidad biológica a largo plazo y la consecución de

una ganadería duradera. Otros ámbitos de trabajo empiezan a perfilarse, entre ellos el de

las vacunas de uso terapéutico en lugar de preventivo y el de la vacunación antitumoral.

Aún es demasiado pronto, sin embargo, para hacer algún tipo de balance al respecto.


Vaccination guidelines: a bridge between officialrequirements and the daily use of vaccines

E. Thiry (1) & M.C. Horzinek (2)

(1) Virology and Viral Diseases, Department of Infectious and Parasitic Diseases, Faculty of VeterinaryMedicine, University of Liège, B-4000 Liège, Belgium. Email: [email protected](2) Veterinary Research Consult, Haydnlaan 15, 3723KE Bilthoven, the Netherlands

SummaryVaccination guidelines are non-compulsory recommendations which assist theveterinary practitioner to use vaccines efficiently. They complement the officialinformation contained in the shortened form of the summary of productcharacteristics that is included in the package insert of the product. The aim ofthis article is to clarify the role of guidelines and examine how they can improvethe use of vaccines in practical conditions. The development of vaccinationguidelines is explained. Several issues are discussed: primary vaccinationschedule; interference with maternally derived antibodies; duration of immunity;vaccination and ageing. Three guidelines dealing with the vaccination of catsagainst upper respiratory tract disease are compared, as an example. Inconclusion, vaccination guidelines are essential tools to assist veterinarians ingood vaccination practices. They fill the gap that exists between the officialrecommendations included in the regulations and the licensing dossiers and thedaily use of the vaccines.

KeywordsCanine – Feline – Guidelines – Vaccine – Virus.

IntroductionVaccination guidelines are non-compulsoryrecommendations which assist the veterinary practitionerto use vaccines efficiently. They complement the officialinformation contained in the summary of productcharacteristics (SPC) that can be found in the packageinsert (an SPC is part of the documentation required for anauthorised medicinal product) (21). However, althoughthe vaccination schedule that appears in the package inserthas been reviewed and approved by the licensingauthorities, the practical use of the vaccine in the field candeviate from this official schedule. Furthermore, newscientific data can modify the vaccination approach, butthe respective changes in the regulations can take severalyears before coming into force. In such cases, guidelinescan serve as a bridge between official and unofficialrecommendations for vaccine use.

The aim of this article is to clarify the role of guidelines andthe ways in which they can ensure that vaccines are usedeffectively in practical conditions. The situation in the

European Union (EU) will be taken as an example. Thefocus on pet animal vaccination is appropriate because it isless regulated by official policy and sanitary measures andmore influenced by the behaviour of veterinarians and petowners. The authors also undertake a comparison of several guidelines independently issued on the same subject.

The role of vaccine producers and national and international authorities in the development andproduction of vaccines has been described and discussedby Jones et al. elsewhere in this issue of the Scientific andTechnical Review (15). Therefore, this paper intends toexplain the increasing role of expert committees inpublishing vaccination guidelines in order to help theveterinarian in his/her daily practice.

Why are guidelines useful?It is important to produce guidelines because the timebetween the initial development of a vaccine and its use in

the field can be very long: several different players becomeinvolved and scientific knowledge develops, so the initialrecommendations for use may no longer be the mostappropriate. In addition, a vaccine is usually used as partof a complex vaccination programme and also in verydiverse field situations, not all of which can bedocumented in the package insert of the product. There aretwo main sets of factors which can affect the use ofvaccines; the first concerns the process of developing andmarketing a vaccine and the second concerns the variety ofdifferent bodies that make recommendations about theirproduction and use. The first is as follows:

a) academic research provides scientific data about the identification of infectious agents, their incidence andthe fulfilment of Koch’s postulates. Pathogenesis andimmunity are also studied and all this scientificinformation is used to stimulate applied research on thedevelopment of vaccines (6);

b) the pharmaceutical company designs a vaccine andcarries out experimental and field studies in order to meetthe requirements of the regulatory authorities for quality,safety and efficacy of the vaccine in a given species, a givenage and for a given vaccination schedule (6);

c) the pharmaceutical company submits a dossier to obtaina marketing authorisation in the EU, which must complywith several regulations: Directives of the EuropeanCommission, monographs of the European Pharmacopoeiaand other international and national rules (8, 9, 26);

d) the veterinary immunological product will follow acentralised or a decentralised procedure for granting amarketing authorisation in the EU (3);

e) when the marketing authorisation is granted, the SPC ofthe vaccine is available in the product information. It givesthe main properties of the compound and the approvedvaccination schedule as it will appear in the package insert.It is based on the results of experiments performed inexperimental stations and field trials carried out by thecompany (21);

f) the product is released on the market and the companyinforms veterinary practitioners through its marketingcommunication; this communication may deviate from theofficially approved recommendations for vaccine use (21);

g) veterinary practitioners may use the vaccination in waysthat are noticeably different from the recommendations ofthe package insert, particulary if it is incorporated in alarger scheme involving other vaccines.

The second set of factors relates to the official and non-official bodies that provide information and/or makerecommendations about the production and use ofvaccines. It can be described as follows:

a) faculties and schools of veterinary medicine as well asother scientific institutes provide scientific knowledge;

b) pharmaceutical companies develop vaccines using theirown scientific and technological data and provide theirown technical information about the product;

c) regulatory authorities publish rules and guidelines andare associated in the writing of regulations regarding theproduction of vaccines in order to guarantee the quality ofthe new veterinary immunological medicinal products(21). Examples of the main regulations that must be takeninto account when preparing and using a new vaccine arethe European Pharmacopoeia, European CommissionDirectives on medicinal products, and, in the United Statesof America, the Code of Federal Regulations (18). Giventhe time that it takes to develop legislation, theseregulations are sometimes not based on the most recentscientific knowledge;

d) various kinds of veterinary associations produceguidelines for the proper use of vaccines in field conditions(12);

e) animal owners and breeder associations can also influence the use of vaccines by veterinarypractitioners (12).

The different sources of information regarding the use ofvaccines explain why a discrepancy can be observedbetween the recommendations of the vaccine packageinsert and its use in the real conditions of veterinarypractice. It is of primary importance that the vaccinationschedules followed by the veterinary practitioners are themost efficacious ones even if this means that they do notstrictly follow the recommendations of the package inserts.

How are guidelines developed?The identified discrepancy between the officialrequirements for vaccine use and the practical use of vaccines in the field has been well recognised andwhether this is acceptable or not should no longer be amatter of discussion. Therefore, there is a need to make a link between the authorised characteristics of the vaccineas described in the SPC and the package insert, thescientific knowledge available in published literature, andthe requirements of veterinary practice. To this end, severalcommittees have been created on the initiative of professional associations or experts in the field. Thesecommittees can be sponsored by pharmaceuticalcompanies but, if they are, they must maintain fullscientific independence from the sponsors. Their objectiveis to produce guidelines for the proper use of vaccines in the field and therefore to propose a coherent vaccinationscheme which does not depend on the individualcharacteristics of licensed products.


The authority of these committees is based on theexperience of their members, who must be recognisedexperts in the field of infectious diseases, vaccination andinternal medicine. Several committees are already at work,for example: the Feline Vaccine Advisory Panel of theAmerican Association of Feline Practitioners (20); theEuropean Advisory Board on Cat Diseases (7) and theGerman Federal Association of Veterinary Practitioners (2).

Guidelines are issued after a long reviewing procedurewhich takes into consideration information from multiplesources such as:

– scientific literature, including scientific articles,conference proceedings and clinical reports providingresults of controlled trials with a strong statisticalsignificance

– vaccine package inserts, based on the marketingauthorisation dossier and controlled experiments carriedout by the company to fulfil the official requirements; theresults of these trials are strictly limited to the productunder testing

– information on the current vaccination practices ofveterinarians (in order to take into account the experiencegained in field conditions)

– information from evidence-based veterinary medicine,which combines the above-mentioned sources of differentlevels of evidence with a pragmatic approach to reach adecision (16).

These committees write general and specificrecommendations for good vaccination practices andremain independent of any brand or any particularcommercial product. They can skip the slow process of thedevelopment of regulations and can therefore makerecommendations on adapting vaccination programmes ona yearly basis according to the latest scientific knowledge.Scientific literature may provide new data on alreadylicensed vaccines or very similar products, and these newdata may differ from those contained in the marketingauthorisation dossier. These committees can modify thevaccination approach and make new recommendationswhich are not strictly supported by either the vaccinemarketing authorisation dossier or the official regulations.For example, they can provide advice on the vaccinevalences to be included in a vaccination programme (theso-called ‘core’ vaccines are recommended for allcompanion animals; ‘non-core’ vaccines should beadministered in specific risk conditions [20, 23]) and makerecommendations on which infectious agents should bevaccinated against depending on the age, the conditionand the environment of the animal (24).

These committees can influence practitioners’ use ofvaccines because they are very close to their needs.

Therefore, they are expected to become more and moreimportant in the future. They could recommend alternativemethods of using the vaccine that are not described in theSPC. This point should be taken into consideration by theofficial drug agencies and, in general, by all regulation-setting institutions. Regulations evolve quite slowlycompared to the rapidly expanding needs of veterinarymedicine and the evolution of scientific knowledge. It islikely that these committees could not only influence thevaccination habits of veterinary practitioners but also theofficial institutions like national and international drug agencies.

What issues do guidelines address?Onset of immunity

Primary vaccination schedule

The SPC gives a minimum age for vaccination, which can,in practice, vary depending on several factors: the age atwhich the puppy or the kitten is shown to the practitionerfor the first time; the behaviour and the environment of theanimal; and the infectious agents that the vaccination isintended to combat.

For instance, vaccination against canine parvovirus (CPV)can start early, at five to six weeks of age. The efficacy of thevaccination at this very young age is influenced by the levelof maternally derived antibodies (MDA). Furthermore, the interval between injections cannot always be strictlyapplied due to practical constraints, and especially if thepet animal is not shown to the practitioner at the appropriate age. Certain combinations of vaccines willalso mean that some deviation from the recommendationsof the vaccine SPC are necessary. Guidelines are needed,therefore, to advise the veterinarian about the best decisionto take in all the various circumstances encountered in practice.

Interference with maternally derived antibodies

At a very young age, MDA can significantly interfere withthe efficacy of vaccination. This is a general statement sinceno individual testing is performed on a regular basis. In thefuture, diagnostic kits to measure the level of MDAinterference will become available for some vaccines andare already in use, for canine distemper virus (CDV) and CPV (25).

At a later age, duration of MDA depends on the level ofimmunity of the bitch or the queen, on the amount of colostrum uptake by the puppies or the kittens(differences between offspring of the same litter) and onthe infectious agent.


For example, vaccine package inserts propose a doublevaccination schedule in cats at 9 and 12 weeks of age forboth feline herpesvirus 1 (FeHV-1) and feline calicivirus(FCV). Knowing that MDA have a prolonged duration,especially for FCV, guidelines can recommend that a thirdround of vaccination be performed at 16 weeks of age (7, 20).

Duration of immunity

In European vaccine SPCs, intervals between vaccinationsare strictly regulated by analysing the results of protectionexperiments at the end of the claimed duration ofimmunity (8, 9).

First booster vaccination

The recommendation for the time of the first boostervaccination is based on the results of the duration ofimmunity experimental studies. It is most often one yearafter the primary vaccination. However, experts cansuggest that cats and dogs be vaccinated earlier, six monthsafter the primary vaccination (7). This statement is basedon the fact that several animals are not properly vaccinatedwith the primary vaccination because of interference byMDA. This intermediate vaccination is designed to preventdogs remaining unprotected over a one-year period.However, such modification remains compatible with thevaccine SPC because revaccination is carried out within thedemonstrated duration of immunity.

Intervals between vaccinations

The current trend is to increase the interval betweenbooster vaccinations. It is supported by several scientificpublications (4, 5), but drug companies are required tocarry out their own experiments and publish their ownresults before any modification can be made to the SPC,and as this is expensive and not in their interest they donot provide the necessary data and SPCs remainunchanged. Performing the first booster vaccination afterone year is highly recommended (14). Taking CDV andcanine adenovirus 2 (CAV-2) as examples, the protectionconferred by attenuated vaccines is long-lasting and mostlikely longer than the duration of the immunity officiallyreported in the vaccine package inserts (14). One challengestudy supports claims that there is a three-year duration ofimmunity after vaccination at 7 and 11 weeks of age (11).CDV and CAV-2 antibodies persist at least four years aftervaccination (17). Other studies suggest that there may bean even longer duration of immunity against these viruses(23). This development is now apparent in the most recentversions of vaccine guidelines, where three-year intervalsbetween rounds of vaccination are usually proposed for‘core’ vaccines (20).

Combination of vaccines Vaccine SPCs do not give any recommendation about thesimultaneous or the sequential use of vaccines sold bydifferent companies. The compatibility between vaccines istherefore a safety concern which is usually not addressedby the package inserts of the products and which needsspecific guidelines. Both safety and efficacy must beconsidered since some vaccine valences may haveinterfering effects that decrease the efficacy of other vaccinecomponents.

In addition, it is the role of guidelines to provide thepractitioner with coherent vaccination programmes(including the all important valences) and to proposemodifications to the vaccine schedule to take account ofvarious different factors such as specific epidemiologicalconditions or the type of animal being vaccinated, e.g.immunodepressed animals, animals in shelters, animals inbreeding colonies, etc. (7, 24). Therefore, guidelines aim toprovide comprehensive advice on vaccination programmesfor both ‘core’ and ‘non-core’ vaccines, justifying their useunder specific conditions.

Vaccination and ageingAgeing is known to increase susceptibility to infectiousdiseases and decrease the efficacy of vaccinations, mainlydue to a partial loss of the antibody response and areduction of T helper lymphocyte activity (10, 19). A fewdata are available in domestic animals (10, 13). However,even the average age when ageing could modify theimmune response is not known for companion animalsand can only be extrapolated from the measurement ofsome physiological modifications. For example, whilemany cats begin to show clinically significant changesbetween the ages of 7 and 10, most of them start to beaffected at 12 years of age (1).

Several recommendations have already been made in theliterature (22). For example, old dogs have high anti-rabiesantibody titres before revaccination, meaning that a goodvaccination schedule applied in the young and adultperiod can efficiently protect aged animals (13). More datashould be made available by other studies in order to bettersubstantiate the vaccination of aged animals. Indeed thismatter is considered neither by regulations nor bypharmaceutical companies and is not properly included invaccination guidelines due to this lack of knowledge (20).

Comparison of three guidelinesThe three sets of guidelines compared here were allproduced to guide the veterinary practitioner in thevaccination of cats. They were produced by the American


Table IComparison of the main features of guidelines on the vaccination of cats against the two viruses involved in upper respiratory tractdisease (feline herpesvirus 1 and feline calicivirus) (2, 7, 20)

CriteriaAmerican Association European Advisory Board German Federal Association of Feline Practitioners on Cat Diseases of Veterinary Practitioners

Primary vaccination schedule Administer two doses, 3 to 4 weeks apart Two vaccinations, at an interval Two vaccinations, at an interval

of 2 to 4 weeks of 3 to 4 weeks

Special recommendations Begin as early as 6 weeks of age, then Vaccination is usually started at around Three vaccinations at 8, 12 and

for primary vaccination every 3 to 4 weeks until 16 weeks of age 9 weeks of age; the second vaccination 16 weeks of age

is administered 2 to 4 weeks later, with

the third given around 12 weeks of age

In high-risk situations, a third vaccination

at 16 weeks should be considered

Booster vaccination schedule A single dose is given one year following At annual intervals Vaccination at 15 months of age is included

– duration of immunity the last dose of the initial series In cases of cats in low-risk situations, in the basic vaccination schedule

Booster vaccinations every three years three-yearly intervals would be

recommended. An informed decision Booster vaccinations every two years

should be made on the basis of a risk–

benefit analysis

Special recommendations In unusual circumstances, if a cat is going Annual boosters are particularly important

to be placed in a known high-risk situation, to cats that may be exposed to high-risk

an additional booster vaccination shortly situations, e.g. boarding catteries

before such risk is encountered may

be considered


Association of Feline Practitioners (20), the EuropeanAdvisory Board on Cat Diseases (7) and the GermanFederal Association of Veterinary Practitioners (2),respectively (Table I). Only certain sections of theseguidelines have been compared, namely, the sections thatdeal with vaccination programmes to protect cats againstupper respiratory tract disease caused by FeHV-1 and FCV.

The differences which can be observed between the threeguidelines can be explained by at least two factors. First,the disease approach is different depending on the countryor the region: the cultural aspects (e.g. with regard to theimportance of animal welfare), the level of medical care ofpet animals and the available vaccines. Secondly, there areso far no definite rules to control infectious diseases andthe expert opinion, as reflected in the guidelines, is alwaysbased on a consensus between experts. This consensusopinion may differ depending on the composition of theexpert panel.

ConclusionsVaccination guidelines are essential tools to helpveterinarians use vaccination effectively. They fill the gap

that exists between the official recommendations issuingfrom the regulations and the licensing dossiers, and thedaily use of vaccines. Vaccines are developed and producedwith the aim of protecting animals against important, oftenlethal, infectious diseases. Therefore, good vaccinationguidelines can improve the quality of the vaccine-inducedprotection in the field, provided they take into accountboth the latest scientific data and knowledge of the practiceconditions.

AcknowledgementsWe would like to offer our sincere thanks to our colleaguesat the European Advisory Board on Cat Diseases, withwhom we had many helpful discussions. We extend ourthanks to Hervé Poulet and Jean-Christophe Thibault(Mérial, Lyons), Angélique Zicola, Marie-Lys Van deWeerdt and Dominique Quatpers (Virology, Faculty ofVeterinary Medicine, University of Liège) for stimulatingdiscussions.


Les lignes directrices de la vaccination : un pont entre les besoinsofficiels et l’utilisation quotidienne des vaccins

E. Thiry & M.C. Horzinek

RésuméLes lignes directrices de vaccination sont des recommandations nonobligatoires qui aident le vétérinaire praticien à utiliser les vaccins de manièreefficace. Elles complètent l’information officielle présente dans la noticed’utilisation du produit et qui peut être retrouvée dans le résumé des caractéristiques du produit. L’objectif de cet article est de clarifier le rôle deslignes directrices et leurs bénéfices dans le cadre d’une bonne utilisation des vaccins dans les conditions de la pratique. Le concept des lignes directricesde vaccination est d’abord expliqué. Plusieurs points d’intérêt sont développés :programme de primo-vaccination, interférence par les anticorps d’originematernelle, durée d’immunité, vaccination et vieillissement. Trois lignesdirectrices traitant de la vaccination du chat contre le coryza félin sont comparées, à titre d’exemple. En conclusion, les lignes directrices sont desoutils essentiels pour aider les vétérinaires dans de bonnes pratiques de vaccination. Elles forment un lien entre les recommandations officiellesémanant des règlements et des dossiers d’enregistrement et l’usage quotidiendes vaccins.

Mots-clésCanin – Félin – Ligne directrice – Vaccin – Virus.

Las directrices de vacunación como nexo entre los requisitosoficiales y el uso cotidiano de las vacunas

E. Thiry & M.C. Horzinek

ResumenLas directrices de vacunación son recomendaciones de aplicación optativa, queayudan al veterinario a utilizar las vacunas de manera eficaz. Representan uncomplemento de la información oficial que figura en el resumen decaracterísticas que acompaña al producto empaquetado. Tras aclarar la funciónde las directrices y explicar el modo en que pueden servir para mejorar el uso delas vacunas en la práctica, los autores exponen el proceso que lleva a suelaboración. Entre los temas tratados figuran el calendario de vacunacionesprimarias, la interferencia con anticuerpos de origen materno, la duración de lainmunidad y la relación entre vacunación y envejecimiento. A modo de ejemplocomparan tres directrices de vacunación de gatos contra la infección del tractorespiratorio superior. Las directrices de vacunación, en suma, son unaherramienta básica para ayudar al veterinario a proceder correctamente aladministrar una vacuna, pues vienen a tender un puente entre el uso cotidianode las vacunas y las recomendaciones oficiales contenidas en los reglamentoso los expedientes de solicitud de licencia.

Palabras claveCanino – Directrices – Felino – Vacuna – Virus.

References1. American Association of Feline Practitioners (AAFP) (2005).

– American Association of Feline Practitioners/Academy ofFeline Medicine panel report on feline senior care. J. felineMed. Surg., 7, 3-32.

2. Anon. (2006). – Deutsche Impfempfehlungen für dieKleintierpraxis [German recommendations for vaccination insmall animal practice]. Bundesverband praktizierenderTierärzte [German Federal Association of VeterinaryPractitioners].

3. Brunko P. (1997). – Procedures and technical requirements inthe European Union. In Veterinary vaccinology (P.-P. Pastoret,J. Blancou, P. Vannier & C. Verschueren, eds). Elsevier,Amsterdam, 674-679.

4. Coyne M.J., Burr J.H.H., Yule T.D., Harding M.J., Tresnan D.B. & McGavin D. (2001). – Duration of immunityin dogs after vaccination or naturally acquired infection. Vet.Rec., 149, 509-515.

5. Coyne M.J., Burr J.H.H., Yule T.D., Harding M.J., Tresnan D.B. & McGavin D. (2001). – Duration of immunityin cats after vaccination or naturally acquired infection. Vet.Rec., 149, 545-548.

6. Desmettre P. & Martinod S. (1997). – Research anddevelopment. In Veterinary vaccinology (P.-P. Pastoret, J. Blancou, P. Vannier & C. Verschueren, eds). Elsevier,Amsterdam, 175-194.

7. European Advisory Board on Cat Diseases (2007). –Guidelines on feline infectious diseases. Available at:www.abcd-vets.org/guidelines/ (accessed on 17 May 2007).

8. European Communities (EC) (2001). – Directive 2001/82/ECof the European Parliament and of the Council of 6 November 2001 on the Community code relating to veterinary medicinal products. Off. J. Eur. Communities, L 311, 28/11/2001, 0001-0066.

9. European Communities (EC) (2004). – Directive 2004/28/ECof the European Parliament and of the Council of 31 March2004 amending Directive 2001/82/EC on the Communitycode relating to veterinary medicinal products. Off. J. Eur.Communities, L 136, 30/04/2004, 0058-0084.

10. Fermaglich D.H. & Horohov D.W. (2002). – The effect ofaging on immune responses. Vet. Clin. North Am. EquinePract., 18 (3), 621-630.

11. Gore T.C., Lakshmanan N., Duncan K.L., Coyne M.J., Lum M.A. & Sterner F.J. (2005). – Three-year duration ofimmunity in dogs following vaccination against canineadenovirus type-1, canine parvovirus, and canine distempervirus. Vet. Ther., 6, 5-14.

12. Hill R.E. (1997). – Role of the consumer in the use andregulation of veterinary biological products. In VeterinaryVaccinology (P.-P. Pastoret, J. Blancou, P. Vannier & C. Verschueren, eds). Elsevier, Amsterdam, 744-762.

13. HogenEsch H., Thompson S., Dunham A., Ceddia M. &Hayek M. (2004). – Effect of age on immune parameters andthe immune response of dogs to vaccines: a cross-sectionalstudy. Vet. Immunol. Immunopathol., 97, 77-85.

14. Horzinek M.C. (2006). – Vaccine use and disease prevalencein dogs and cats. Vet. Microbiol., 117, 2-8.

15. Jones P.G.H., Cowan G., Gravendyck M., Nagata T., Robinson S. & Waits M. (2007). – Regulatory requirementsfor vaccine authorisation. In Animal vaccination. Part 2:scientific, economic, regulatory and socio-ethical issues (P.-P. Pastoret, M. Lombard & A.A. Schudel, eds). Rev. sci.tech. Off. int. Epiz., 26 (2), 379-393.

16. Kastelic J.P. (2006). – Critical evaluation of scientific articlesand other sources of information: an introduction to evidence-based veterinary medicine. Theriogenology, 66, 534-542.

17. Mouzin D.E., Lorenzen M.J., Haworth J.D. & King V.L.(2004). – Duration of serologic response to five antigens indogs. J. Am. vet. med. Assoc., 224, 55-60.

18. Pastoret P.-P. & Falize F. (1999). – Viral veterinary vaccines.Dev. biol. Stand., 101, 73-78.

19. Plowden J., Renshaw-Hoelscher M., Engleman C., Katz J. &Sambhara S. (2004). – Innate immunity in aging: impact onmacrophage function. Aging Cell, 3, 161-167.

20. Richards J.R., Elston T.H., Gaskell R.M., Hartmann K., Hurley K.F., Lappin M.R., Levy J.L., Rodan I., Scherk M.,Schultz R.D. & Sparkes A.W. (2006). – The 2006 AmericanAssociation of Feline Practitioners Feline Vaccine AdvisoryPanel Report. J. Am. vet. med. Assoc., 229, 1405-1441.

21. Roberts B. & Sanders A. (1997). – Registration andmarketing. In Veterinary vaccinology (P.-P. Pastoret, J. Blancou, P. Vannier & C. Verschueren, eds). Elsevier,Amsterdam, 243-254.

22. Schultz R.D. (1982). – Theoretical and practical aspects of animmunization program for dogs and cats. J. Am. vet. med.Assoc., 181, 1142-1149.

23. Schultz R.D. (2006). – Duration of immunity for canine andfeline vaccines: a review. Vet. Microbiol., 117, 75-79 .

24. Thiry E. (2006). – Clinical virology of the dog and cat.Editions du Point Vétérinaire, Paris.

25. Twark L. & Dodds W.J. (2000). – Clinical use of serumparvovirus and distemper virus antibody titers fordetermining revaccination strategies in healthy dogs. J. Am.vet. med. Assoc., 217, 1021-1024.

26. World Organisation for Animal Health (OIE) (2004). –Manual of Diagnostic Tests and Vaccines for TerrestrialAnimals (mammals, birds and bees), 5th Ed. OIE, Paris.



Recommendations of the OIE International

Conference on the Control of Infectious

Animal Diseases by Vaccination, Buenos Aires,

Argentina, 13 to 16 April 2004

A.A. Schudel (1) & M. Lombard (2)

(1) Urraca 1366, Carilo (7167), Partido de Pinamar, Provincia de Buenos Aires, Buenos Aires, Argentina.

Email: [email protected]

(2) Consultant in Biologicals, 22, rue Crillon, 69006, Lyons, France

IntroductionIn recent years, epidemics of emerging and re-emerginginfectious animal diseases and zoonoses have often beencontrolled by implementing a policy of mass slaughter.However, this approach to disease control posesconsiderable ethical, technical, ecological and economicproblems and there is a need for alternative controlstrategies. Therefore, in 2004, the World Organisation forAnimal Health (OIE), the International Association forBiologicals (IABS), and the National Animal Health Servicein Argentina (Servicio Nacional de Sanidad Animal)organised an international conference on the control ofinfectious animal diseases by vaccination. The conferencewas held in Buenos Aires, Argentina, from 13 to 16 Apriland was attended by over 300 scientists from some 50 countries.

RecommendationsThe recommendations of the Conference attendees (1)support the position that veterinary vaccinology can helpto build a better world, particularly given the quality of theveterinary biologics available today.

Considering that:

1. Preventing the spread of animal disease throughinternational trade of animals and animal products is oneof the primary missions of the OIE. This is accomplishedby establishing and updating international standards andguidelines that prevent the spread of pathogens whileavoiding unjustified sanitary barriers.

2. The OIE standards for terrestrial animals are containedin the Terrestrial Animal Health Code (the Terrestrial Code)and the Manual of Diagnostic Tests and Vaccines forTerrestrial Animals (the Terrestrial Manual).

3. The collection, analysis and dissemination ofveterinary scientific information is also one of the mainmissions of the OIE.

4. The standards developed by the OIE are recognised asinternational standards for animal health and zoonoses bythe Agreement on the Application of Sanitary andPhytosanitary Measures (SPS) of the World TradeOrganization (WTO).

5. Infectious animal diseases and zoonoses represent amajor constraint to the maintenance and development oflivestock and present a major threat to public health, to

the livelihood of farmers (especially in developingcountries) and to national economies.

6. Over the past few years, the world has witnessed theemergence and re-emergence of several infectious animaldiseases that have had a major impact on animal andhuman health. These have severely affected the economy inboth developed and developing countries.

7. New scientific and technological knowledge about theprevention of many of these infectious diseases couldcontribute to the development of safer and moreefficacious vaccines and diagnostic tests.

8. For ethical, ecological and economic reasons, it is nolonger acceptable to control and eradicate diseaseoutbreaks mainly by applying a policy of mass slaughter.

9. Vaccines help to improve animal health, public health,animal welfare, and agricultural sustainability, thusprotecting the environment, maintaining biodiversity, andprotecting consumers of animal products.

10. The OIE, being the international referenceorganisation for animal health and zoonoses has, whereverpossible, incorporated into its standards, the best ‘state ofthe art’ scientific knowledge on the use of appropriatediagnostic tests, disease prevention and control byvaccination.

11. Vaccination is without doubt one of the most usefulmeasures which can be used to prevent animal diseases,and since its inception veterinary science has been stronglylinked with the development of vaccinology.

12. Vaccination has proved that it is capable of preventing,controlling and eradicating disease, as exemplified by thecontrol of smallpox, rinderpest and rabies.

13. Recent scientific advances in the diagnostic field, inparticular the ability to differentiate vaccinated animalsfrom those that have undergone pathogen replication as aresult of natural challenge, have been recentlyincorporated into the Terrestrial Manual. Their implicationshave either already been reflected or are currently beingdiscussed by the OIE in order to amend those sections ofthe Terrestrial Code which deal with disease control andrecovery of disease-free status after an occurrence of adisease.

14. This International Conference is based on the valuableexperience gained in the control and elimination of footand mouth disease and other significant animal diseasesand zoonoses through the use of vaccination.

15. The Conference is an opportunity for the exchange ofthe latest scientific information at the global level that will,

at the same time, assist in the evaluation and improvementof the current OIE standards and guidelines for bettercontrol of animal infectious diseases.

16. For this event, the OIE has acted in collaboration withthe IABS, which has a long and valuable tradition in thedissemination of the most relevant scientific informationon human and animal health.

Conference attendees of the OIE International Conference on the Control of Infectious Animal Diseases by Vaccination recommend the following:

1. Current approaches to animal disease prevention,control, and eradication by vaccination should bereviewed, wherever possible, according to the latestscientific information and incorporated into the OIEstandards, recommendations and guidelines in order tofacilitate both animal disease control and trade in animalsand animal products.

2. Whenever feasible, the OIE should formulatevaccination policies as an alternative to the massslaughtering of animals.

3. Greater emphasis should also be placed on the use ofvaccination for the control of food-borne and otherzoonotic diseases in animals in order to safeguard publichealth. This may include wildlife reservoirs of pathogens.

4. The OIE should develop and incorporate into itsstandards, recommendations and guidelines all relevantnew information on diagnostic tests and the effectiveprevention, control and subsequent eradication ofinfectious animal diseases by vaccination.

5. The OIE should ask Member Countries to produce anduse vaccines manufactured, tested and approved accordingto OIE standards and guidelines in order to improve theirsafety and potency. The same principles should apply todiagnostic tests.

6. The OIE should encourage Member Countries tostrengthen the capacity of their antigen and vaccine banksto control emerging or re-emerging infectious diseases andzoonoses.

7. The OIE should recommend the development of moreflexible marketing authorisation regulations in order to beable to adapt vaccines to the epidemiological situation inthe field when facing pathogens with multiple serotypes, asexemplified by vaccines against human influenza(provided good epidemiological tools are in place).


8. The OIE should support all research efforts inveterinary vaccinology and encourage funding agencies toput research into new veterinary biological products ontheir agendas and make it a priority. Public research is stillneeded to fill the gap where the private sector does notinvest in new products due to the lack of foreseeninvestment return.

9. The OIE should provide, on official request fromMember Countries, international standards and generalinformation on the availability of antigen and vaccinebanks.

10. The OIE should encourage other international andregional organisations to adopt a similar approach in the

control and eradication of other infectious animal diseasesby vaccination.

11. The OIE and the IABS should disseminate allinformation concerning the International Conference toOIE Member Countries, international and regionalorganisations, and other stakeholders.

12. The OIE should refer the scientific informationgenerated and discussed at this International Conference,including these recommendations, to the OIE RegionalCommissions and relevant Specialist Commissions beforesubmission for endorsement by the OIE InternationalCommittee.


References1. Schudel A.A. & Lombard M. (eds) (2004). – Control of

infectious animal diseases by vaccination. Proc. OIEConference, Buenos Aires, Argentina, 13-16 April 2004. Dev. Biol. (Basel), 119.


Vaccines and OIE listed diseases

A.A. Schudel

Urraca 1366, Carilo (7167), Partido de Pinamar, Provincia de Buenos Aires, Buenos Aires, Argentina.

Email: [email protected]

OIE activitiesThe activities of the World Organisation for Animal Health(OIE) in relation to the prevention and control ofinfectious animal diseases are primarily focused on thefollowing areas:

– collection, analysis and dissemination of veterinaryscientific information in a timely and transparent manner

– promotion of technical assistance and the strengtheningof international cooperation for the enhancement of thecontrol and eradication of animal diseases worldwide

– improvement of the legal framework and capacitybuilding of official Veterinary Services, especially indeveloping countries

– promotion of safe trade in animals and animal productsby eliminating the unjustified barriers that are sometimesput in place as a result of animal diseases, whileminimising the entry of pathogens into importingcountries.

These activities are principally carried out through thedevelopment and application of standards,recommendations and guidelines. The OIE is regarded bythe Sanitary and Phytosanitary Agreement of the WorldTrade Organization (WTO) as the only internationalorganisation responsible for setting standards on animaldiseases, including zoonoses.

OIE standardsThe procedure adopted by the OIE to create or update astandard is complex, but fully transparent. The request tocreate or update a standard can come from an OIEDelegate, a Specialist Commission, the OIE InternationalCommittee or any other authority following the outbreakof a disease or any significant epidemiological event. Onreceipt of the request, the OIE Central Bureau forwards itto the relevant Specialist Commission. The Commission

reviews the request or problem and may seek expertopinion from other experts or Commissions or may decideto refer it to an ad hoc group of specialists for considerationand advice. The final advice or suggestion is reviewed bythe Specialist Commission, which then proposes a drafttext for an appropriate standard to be developed. This drafttext is then circulated to all OIE Member Countries, whichare given sixty days to comment on the proposal. Thecomments are considered by the Commission, which maydecide to withdraw the text altogether or to make certainamendments to accommodate the comments received. Therevised version is then submitted to the InternationalCommittee during the General Session in May fordiscussions and subsequent adoption. Once adopted, itbecomes an OIE standard.

The OIE standards are contained in the Terrestrial AnimalHealth Code (the Terrestrial Code), the Aquatic Animal HealthCode (the Aquatic Code), the Manual of Diagnostic Tests andVaccines for Terrestrial Animals (the Terrestrial Manual) andthe Manual of Diagnostic Tests for Aquatic Animals (theAquatic Manual) (1, 2, 3, 4).

Terrestrial Animal Health Code/Aquatic Animal Health Code

One of the main purposes of the Codes is to reduce the riskof the spread of infectious animal diseases or agentsthrough the international trade of animals and animalproducts while at the same time facilitating safe trade.Through its Early Warning Disease Information System,the OIE promptly contacts its Member Countries viaemails, faxes or other means of communication to informthem (in the official languages of the OIE) of theoccurrences of major animal diseases in the world. Thisallows countries at risk, i.e. neighbouring countries orthose importing animals or animal products from theinfected country to take appropriate measures to preventthe entry of pathogens into their territory.

The Codes contain some generic chapters dealing withgeneral issues (e.g. obligations and ethics in international

trade, import risk analysis, principles of epidemio-surveillance with respect to specific diseases) and otherchapters are devoted to specific diseases. Each diseasechapter spells out the requirements for a country or zoneto be considered free from the disease and lists thecommodities that can be safely traded irrespective of thedisease status. It also describes the health measures to befollowed by importing countries when importing liveanimals and specific animal products from countries orzones where the disease exists. Importing countries arestrongly urged to follow the recommendations prescribedby the OIE. However, it is the sovereign right of animporting country to apply stricter controls or a higherlevel of protection. In such cases, and in accordance withWTO rules, the importing country has to carry out ascience-based risk assessment to demonstrate clearly whyit wants to apply a higher level of protection. The OIEstandards provide Member Countries with the appropriateguidance to apply an import risk analysis. As is clearlyindicated in the OIE standards, the mere presence of adisease in an exporting country does not provide fulljustification for a total ban on animals or animal productsfrom that country. Instead, a decision on whether or not toaccept imports from infected countries should be based onthe results of an import risk analysis. This is how, undercertain conditions, countries with bovine spongiformencephalopathy (BSE) and foot and mouth disease (FMD)can continue to export meat and meat products.

The OIE also has an in-house dispute settlement system toresolve technical or scientific conflicts that may ariseamong Member Countries. This mediation system isscience-based and is quick, effective and less costly thanthe complex system in place at the WTO.

Manual of Diagnostic Tests and Vaccines

The OIE Terrestrial Manual is a companion volume of theTerrestrial Code. It also contains some generic chaptersdealing with important issues such as:

– sampling methods

– quality management of veterinary laboratories

– principles of validation of diagnostic tests

– tests for sterility and freedom from contaminants

– human safety in veterinary vaccine manufacture

– biotechnology in the diagnosis of infectious diseases

– the role of official bodies in the international regulationof veterinary biologicals.

Other chapters are devoted to specific diseases. Thesechapters include the prescribed tests for international tradeand alternative tests that can be used under a bilateral

agreement between importing and exporting countries.The aims of the Terrestrial Manual are to facilitate theinternational trade of animals and animal products andalso to contribute to the improvement of animal healthservices and the control of animal diseases byinternationally recognised measures. It spells out therequirements for the manufacture and quality control ofanimal vaccines, including vaccines for 48 of the OIE listeddiseases. The guidance on the requirements for vaccinemanufacture lays emphasis on:

a) Seed management:

– characteristics of the seed

– method of choice

– validation as a vaccine.

b) Method of manufacture:

– in-process control

– batch control

– sterility

– safety

– potency

– duration of immunity

– stability

– preservatives

– precautions (hazards).

c) Tests on final products:

– safety

– potency

– purity.

The Terrestrial Manual also describes the various diagnostictests that are recognised not only to prove the presence ofdisease but also the tests that can be used to demonstratefreedom from infection or absence of virus circulation. Inthis respect, the diagnostic tests that have recently beendeveloped for the diagnosis and control of certain diseasessuch as FMD, classical swine fever, Aujeszky’s disease andavian influenza have received considerable attention fromthe OIE. The Terrestrial Manual recognises the applicationof marker vaccines and the accompanying diagnostic teststhat serve to differentiate vaccinated from infected animals(DIVA tests). These tests have in a certain wayrevolutionised disease control in that in certain conditionsthey help avoid the mass killing of animals, which posesethical, ecological and economic problems. They have alsoimmensely contributed to international trade, becauseinfected countries can use vaccination as an additional toolto control important animal diseases and continue withtrade, provided of course that vaccinated animals areclearly identified and only healthy animals are vaccinated.These tests are also accepted by the OIE for the recovery ofcountry disease status. In the case of FMD, non-structural


protein (NSP) tests are now validated as screening tests andcan be used to demonstrate absence of virus circulation. Asregards Aujeszky’s disease, the absence of gE antibodies invaccinated pigs is accepted by the OIE as evidence ofabsence of virus circulation. Similarly, the OIE Ad hocGroup of experts on avian influenza has proposed thatvaccination be used as an additional tool in the control ofthe disease, provided that DIVA tests are applied todemonstrate the absence of circulating virus. This shouldalso enable trade of poultry and poultry products tocontinue from countries or zones which have experiencedthe disease.

Future developmentsThe OIE continues to work towards creating vaccine andantigen banks which will be useful to Member Countrieson a national, regional and international basis. These banks

will not compete with the existing vaccine banks but willcomplement them by including vaccines against diseaseswhich are of particular relevance to developing countries.It is also the intention of the OIE, together with its worldnetwork of Reference Laboratories and internationalexperts, to pursue research on DIVA tests to enable thesetests to cover as many animal diseases as possible.

To date there are no vaccines recommended in the Manualof Diagnostic Tests for Aquatic Animals.


References1. World Organisation for Animal Health (OIE) (2004). –

Manual of Diagnostic Tests and Vaccines for TerrestrialAnimals, 5th Ed. OIE, Paris.

2. World Organisation for Animal Health (OIE) (2006). –Aquatic Animal Health Code, 9th Ed. OIE, Paris.

3. World Organisation for Animal Health (OIE) (2006). –Manual of Diagnostic Tests for Aquatic Animals, 5th Ed. OIE,Paris.

4. World Organisation for Animal Health (OIE) (2006). –Terrestrial Animal Health Code, 15th Ed. OIE, Paris.