Journal of Medical Virology 18:69-79 (1986)

A Controlled Trial for Evaluating Two Live Attenuated Mum ps-Measles Vaccines (Urabe Am 9-Schwarz and Jeryl Lynn- Moraten) in Young Children Therese Popow-Kraupp, Michael Kundi, Franz Ambrosch, Hanns Vanura, and Christian Kunz

Institute of Virology (TP.-K., C. K.), Institute of Environmental Hygiene (M. K.), Institute for Specific Prophylaxis and Tropical Medicine (FA.), University of Vienna, and Department of Pediatrics (H. V) , Tuiin, Austria

A prospective, randomised clinical trial was conducted to evaluate the efficacy of two live attenuated mumps-measles vaccines, the Urabe Am 9-Schwarz and the Jeryl Lynn-Moraten vaccine, in 400 young children aged 9 months-4.5 years (median 13.4 months). Antibody responses to both vaccine components were measured by the enzyme-linked immunosorbent assay (ELISA); 96.9% of the seronegative children who received the Urabe Am 9-Schwarz vaccine showed satisfactory mumps antibody responses compared to 90% of the Jeryl Lynn- Moraten vaccine recipients (P < .01). Similar proportions of both groups, 98.5% and 96.8%, respectively, developed measles virus specific antibodies. Both vac- cines were equally well tolerated and clinically acceptable.

Key words: live attenuated measles-mumps vaccines, seroconversion rate, ELISA

INTRODUCTION

The high morbidity of measles and mumps and the various complications of these infections have led to the development of effective live attenuated vaccines [Krugman et al, 1965; Weibel et al, 1967; Buynak and Hilleman, 1966; Isomura et al, 19731. Subsequently, Weibel et a1 [ 19731 demonstrated that mumps and measles vaccines could be combined without altering the immunological response to either component. This simplified vaccine supply and its administration and increased the acceptance rate. One of the first and up to now the most widely used measles-mumps vaccines contains the attenuated measles virus strain Moraten and the attenuated mumps virus strain Jeryl Lynn. More recently, another attenuated mumps vaccine strain, Urabe Am 9, which was developed in Japan, has been introduced [Yamanishi

Accepted for publication August 18, 1985.

Address reprint requests to Therese Popow-Krdupp, Institute of Virology, University of Vienna, Kinder- spitalgasse 15, A-1095 Vienna, Austria.

GI 1986 Alan R. Liss, Inc.

70 Popow-Kraupp et al

et al, 19731. Since then several studies have demonstrated the immunogenicity of this vaccine strain [Popow-Kraupp et al, 1982; Ehrengut et al, 1983; Vesikari et al, 19831. Furthermore it has been reported that the combined administration of this mumps vaccine strain and the Schwarz measles vaccine strain induces an excellent immune response in young children [Vesikari et al, 19831. In order to evaluate combined mumps-measles vaccines in the target population of young children aged 14-20 months , we have conducted a prospective randomised clinical trial comparing the reactogenicity and immunogenicity of the Urabe Am 9-Schwarz vaccine (UAS) with the Jeryl Lynn-Moraten vaccine (JLM), using the enzyme-linked immunosorbent assay (ELISA) for measuring vaccine-induced antibodies [Leinikki et al, 1979; Sakata et al, 1984; Kuno-Sakai et al, 19841.

MATERIALS AND METHODS Study Participants

A total of 400 healthy children of both sexes, aged 9 months to 4.5 years, were vaccinated from April 1981 to April 1982 with one of the two mumps-measles vaccines under study. Requirements for inclusion in the study were (1) informed consent of the parents; (2) no clinical history of mumps and measles or vaccination against these diseases; and (3) absence of medical contraindications to immunization with a live attenuated virus vaccine.

Vaccines Used (1) Mumps-measles Urabe Am 9-Schwarz vaccine (RimparixR) produced by

Smith-Mine RIT (batch No. MM02A41). Mean infectivity titres per vaccine dose: mumps virus Id TCIDsO, measles virus lo4 TCIDSO.

(2) Mumps-measles Jeryl Lynn-Moraten vaccine (MMVAXR) produced by Merck Sharp & Dohme (batch No. 7060). Mean infectivity titres per vaccine dose: mumps virus lo5 TCIDSo, measles virus lo4 TCIDSO.

Study Design

The study was performed under single-blind conditions. The subjects were allocated at random to receive either UAS vaccine (group 1) or JLM vaccine (group 2), respectively. The vaccine recipients were given consecutive numbers and were then assigned to group 1 or group 2, respectively, by using a table of random numbers.

On day 0, a physical examination and temperature recording were carried out. Capillary blood samples were taken for serology by finger prick and 0.5 ml of the freshly reconstituted vaccines were administered subcutaneously to each of the 400 subjects according to the randomisation protocol. Signs and symptoms listed below were observed by the parents of the vaccinees and recorded on individual check lists for a period of 28 days after vaccination.

Local reactions: pain at the injection site, induration, swelling, erythema, itching or other cutaneous signs.

Systemic reactions: fever (more than 37.5"C), chills, sore throat, rash, cough, diarrhea, vomiting and conjunctivitis.

Physical signs: parotid and/or submaxillary swelling, cervical lymphadenopathy. Capillary blood samples were taken for serology between days 29 and 230

postvaccination (median 91 days postvaccination for both groups of vaccine recipients).

Evaluation of Two Mumps-Measles Vaccines 71

Serological Tests

Mumps and measles antibody concentrations were determined by ELISA. The serological assays were performed blindly.

ELISA antigens. Mumps virus antigen was prepared as described previously [Popow-Kraupp, 198 11. Briefly: mumps-virus-infected allantoic fluid was used as antigen source. The Enders strain of mumps virus was propagated as described by Henle [ 19691. After seven days at 33 "C allantoic fluid was harvested and the virus was concentrated by centrifugation at 60,OOOg for one hour at 4°C and resuspended in approximately 1/200 of the original volume in phosphate-buffered saline (PBS pH 7.4). Allantoic fluid from uninfected eggs was treated in the same way and served as control antigen.

Measles virus antigen was produced as described by Forghani and Schmidt [ 19791. Measles-virus (No. 1677, Behringwerke Marburg, FRG)-infected rhesus monkey kidney cells (LLC-MK2 cells, Flow Laboratories, Rockville, MD) were dislodged into the culture fluid by shaking with glass beads, and the cellular debris was then removed by centrifugation at 700g for 30 minutes at 4°C. The virus was concentrated from the supernatant fluid by centrifugation at 78,OOOg for three hours and the resulting pellet was resuspended in approximately 1/5OO of the original volume in 0.01 M tris (hydroxymethy1)aminomethane (Tris)-O.15 M NaCl buffer, pH 9.0, containing 0.002 M ethylenediaminetetraacetate. Control antigen was prepared from uninfected cell cultures in the same manner.

The optimal concentrations of mumps and measles virus antigen for coating the microtitre plates were determined by checkerboard titration.

Test procedure. The ELISA was performed in polystyrene U-shaped microtitre plates (Nunc, Kamstrup, Denmark). The outer rows and columns were not used; 50 pl of antigen and control antigen diluted in carbonate-bicarbonate buffer, pH 9.6, was added to each of the inner wells of the plates, and plates were then incubated overnight at 4°C. The coating solution was then removed and the plates were incubated for one hour at 37°C with 100 p1 PBS, pH 7.4, containing 2% sheep serum. The wells were emptied and 50 pl of the test serum diluted in PBS, pH 7.4, containing 2% Tween 20 and 2% sheep serum, was added. Pre- and postvaccination sera were assayed in duplicate at a serum dilution of 1: 160. After an incubation period of two hours at 37"C, the plates were washed thoroughly with PBS, pH 7.4, and 50 pl per well of horseradish peroxidase-conjugated heavy-chain-specific goat antibodies against hu- man IgG (Nordic Immunological Laboratories, Lausanne, Switzerland) was added. After another incubation period of two hours at 37°C and the washing procedure, 50 pI of substrate (0-phenylenediamine, 1 mg/ml in 0.1 M phosphate-citrate buffer, pH 5.0, containing I p1 perhydrol per ml) was added. The reaction was allowed to proceed at room temperature in the dark for 30 minutes and was then stopped by the addition of 100 pl of 2 N H2S04. Absorbance at 492 nm was measured by the use of a multichannel photometer (Multiscan, Flow Laboratories, Bonn, FRG). The specific absorbance represents the difference between absorbance obtained with antigen and control antigen.

Test results. ELISA results were expressed as specific absorbance at 492 nm (OD) and as units derived by reference to a standard curve (U). This provides a relatively accurate and economic method for estimating virus specific antibodies from a single dilution of serum samples, eliminating systemic components of error and

72 Popow-Kraupp et a1

providing analytical consistency [Malvano et al, 1982, Bishop et al, 19841. The standard curves for the determination of mumps and measles virus specific antibody concentrations were established as follows: Strongly IgG-positive mumps and measles convalescent sera were defined as containing 3,200 arbitrary units, and subsequently, artificial standard sera were derived from these sera by diluting them 1:2, 1:4, 1:8, 1:16, 1:32, and 1:64 in negative serum. In each test these artificial standard sera were assayed in duplicate at the same dilution as the test sera (1 : 160). The standard curve was established by plotting the specific ODs of each dilution versus the corresponding arbitrary units on semilog paper. Test sera were evaluated by comparing their specific ODs with the corresponding OD of the standard curve. Serum samples containing high titres of virus specific antibodies resulting in specific ODs outside the linear part of the standard curve were diluted further.

Test criteria. Sera were considered positive if they contained at least 150 arbitrary units (minimal specific OD = 0.17) of mumps antibodies and at least 100 arbitrary units (minimal specific OD = 0.1) of measles antibodies. These figures were derived from the evaluation of 240 sera from 12-month- to 2-year-old children without a history of mumps virus infection or vaccination and of 210 sera from children of the same age without a history of measles virus infection or vaccination. The positive-negative cutoff represents the 95th percentile point estimated from the distribution function of the arbitrary units in these assays.

Statistical analysis. The Mann-Whitney-U-test, the Fisher-test, and the chi- square-test were used for the assessment of the differences between the two groups of vaccine recipients concerning the characteristics of the vaccinees (number of children per group, age, sex, number of days from vaccination to serum sampling), the number and percentage of vaccine recipients with seroconversion, the median number of arbitrary units, the median of specific ODs at 492 nm, and the clinical findings within a period of 28 days following vaccine administration.

RESULTS Characteristics of the Study Group

A total of 400 healthy children without a clinical history of mumps and measles or vaccination against these diseases were vaccinated according to the randomisation protocol with one of the two vaccines under study. The characteristics of the 400 randomised infants are shown in Table I; 202 of the study participants were vaccinated with the UAS vaccine (= group 1), and 198 received the JLM vaccine (= group 2). No significant difference was found between the two groups with regard to sex (Fisher-test), age (Mann-Whitney-U-test z = 0.32), and the time interval of drawing the postvaccination sera (Mann-Whitney-U-test z = 0.576).

Antibody Response Following the Administration of the Two Vaccines

Pre- and postvaccination serum samples from 199 vaccine recipients of group 1 (UAS vaccine) and from 193 of group 2 (JLM vaccine) were available for the screening of mumps virus specific antibodies (Table 11). Six of the children (1.5%), three in each group, were found to have preexisting mumps virus specific antibodies. Two of these (13 and 15 months of age) had high levels of mumps virus antibodies (3,200 and 1,100 units) in their prevaccination sera and were therefore thought to have been previously infected with mumps virus. After vaccination, no significant

Evaluation of Two Mumps-Measles Vaccines 73

TABLE I. Characteristics of the Study Group"

Group 1 Group 2 (Urabe Am 9-Schwarz (Jeryl Lynn-Moraten

- vaccine) vaccine)

No. of vaccinees 202 198 Sex (M:F) 102 (50.5%):100 (49.5%) 99 (50%):98 (49.5%)

Age (months) Sex not reported 9 1

Median 13.3 13.4 Range 1 1.8-54.3 9.3-51.9

No. of vaccinees 12-18 months (%) 167 (82.7) 167 (84.3) > 24 months (%) 8 (4.0) 9 (4.5)

No. of days from vacc to serum sampling

Median 91 91 Not reported 3 7

Range 29-230 50-188 No. of samples

drawn 60- 120 dpv" (%) 163 (81.9) 158 (82.7) 150 dpv (%) 9 (4.5) 13 (6.8)

*No significant difference between groups as determined by Mann-Whitney U-test or Fisher-test (sex- distribution). Vacc, vaccination. "dpv, days past vaccination.

increase in the mumps virus antibody concentration was detectable in these two children. The other four children, aged 1-2.4 years, had only low levels of mumps antibodies (150-200 U) in their prevaccination sera, probably caused by the presence of crossreacting parainfluenza virus specific IgG antibodies [Chanock et al, 1960; Lenette et al, 1963; Ukkonen et al, 1980; Meurmann et al, 19821. All of them had rises in antibody levels following vaccine administration (400-900 U); 190 (96.9%) of the 196 seronegative children, who received the UAS vaccine, showed satisfactory mumps antibody responses (Table 11) compared with 171 (90%) of the 190 seronega- tive JLM vaccine recipients (P < .Ol).

Pre- and postvaccination sera from 200 children from group 1 and from 193 children from group 2 were available for testing in the measles ELISA (Table 11); five in each group had preexisting measles virus specific antibodies. Four of them (1.2- 2.3 years of age) had high concentrations of measles antibodies in their prevaccination sera (1,500-3,200 U), indicating a previous measles virus infection. The prevacci- nation serum samples from the other six children (aged 0.9-1.1 years) contained only a low concentration of measles antibodies (100 U), most probably indicating residual transplacentally acquired serum antibodies [Albrecht et al, 19771. All of them devel- oped satisfactory antibody responses following the administration of the vaccines (440-1,800 U); 192 (98.5%) of the 195 seronegative children of group 1 and 182 (96.8%) of the 188 seronegative children of group 2 developed measles virus specific antibodies following vaccine administration (Table 11). Of the 191 double-seronegative vaccine recipients of group 1, 183 (95.8%) showed satisfactory antibody responses to both vaccine components compared to 158 (86%) of the 183 double-seronegative children of group 2 (P < .00l) (Table 11).

After administration of the UAS vaccine the median amount of mumps virus antibody units and specific absorbance values were higher than those after the

74 Popow-Kraupp et al

TABLE I1 Mumps and Measles Antibody Responses to Combined Mumps-Measles Vaccines in Young Seronegative Children

No. of No. of vaccine vaccine

recipients No. of No. of recipients with pre- AB-pos AB-neg with sero- and post prevacc vacc conversion

Vaccine used vacc sera sera recipients (%)

Mumpsa Urabe Am 9-Schwarz (group 1: n = 202) 199 3b 196 190 (96.9) Jeryl Lynn-Moraten (group 2: n = 198) 193 3b 190 171 (90.0)

Urable Am 9-Schwarz (group I : n = 202) 200 5d 195 192 (98.5) Jeryl Lynn-Moraten (group2: n = 198) 193 5d 188 182 (96.8)

Urabe Am 9-Schwarz (group 1: n = 202) 199 8 191 183 (95.8) Jeryl Lynn-Moraten (group 2: n = 198) 191 8 183 158 (86.0)

Measles‘

Mumps and measlese

aChi-square test: x2 = 8.475, P < .01. ‘2 150U. ‘Chi-square test: x2 = 1.140, ns, not significant.

eChi-square test: ,y2 = 11.236. P < .001.

TABLE 111. Median No. of Arbitrary Units and of Absorbance Values at 492 nm in Pre- and Postvaccination Sera of Young Seronegative Children, Vaccinated with Combined Mumps-Measles Vaccines

d 2 100u.

Urabe Am Jeryl Lynn- 9-Schwarz Moraten

vaccine vaccine Significancea

Mumps Absorbance prevacc sera 0.019 Absorbance postvacc sera 0.91

Units postvacc sera 710 Units prevacc sera 0

Absorbance prevacc sera 0.002

Units prevacc sera 0 Units postvacc sera 597.1

Measles

Absorbance postvacc sera 0.39

aMann-Whitney U-test. ns, not significant.

0.027 z = 1.86 ns 0.698 z = 2.36 P < .05 0 z = 0.073 ns

458.3 z = 3.91 P < ,001

0.002 z = 1.03 ns 0.415 z = 1.15ns 0 z = 0.058 ns

693.3 z = 1.64 ns

application of the JLM vaccine (Table 111). This is also reflected in the diagram of the frequency distribution of mumps virus antibody units in postvaccination sera (Fig. I ) , which shows that the vaccine recipients of group 1 developed relatively higher amounts of mumps virus antibodies than those of group 2.

No significant difference were found between the median amount of measles virus antibody units and the specific absorbance values of the postvaccination serum samples of the two groups (Table 111). The small but insignificant difference between

Evaluation of Two Mumps-Measles Vaccines 75

30,

20.

10.

MUMPS %

401

UAS -VACCINE

I 30 2oh 10

A

401

M E A S L E S %

401

JLM -VACCINE

B

4 0 1

E L I S A U n l l s

Fig. 1. Frequency distribution of mumps and measles virus specific antibody units of the scrum samples drawn after administration of the Urabe Am 9-Schwarz and the Jeryl Lynn-Moraten vaccine.

the two vaccines in the antibody response to the measles components can also be seen from the frequency distribution of measles virus antibody units in the postvaccination sera (Fig. 1).

Reactions to the Vaccines The signs and symptoms following the administration of the two mumps-measles

vaccines are summarized in Table IV. Individual check lists containing the different adverse reactions were available from 392 (98%) of the 400 vaccinated children (200 in group I and 192 in group 2). Similar proportions of both groups (56.5% of group 1 and 53.1 % of group 2) reported symptoms within 28 days after vaccination. In both groups, fever (at least one temperature recording more than 37.5"C) was the predom- inant systemic symptom, with the peak incidence between day 8 and day 13 after vaccination. Cough and rash, besides nonspecific and to the vaccination unrelated

76 Popow-Kraupp et a1

TABLE IV. Clinical Findings Within a Period of 28 Days Following the Administration of MumDs-Measles Vaccines to Young Children*

Group 1 Group 2 (Urabe Am 9-Schwarz vaccine, (Jeryl Lynn-Moraten vaccine,

Clinical findings N = 200) N = 192)

Systemic reactions (%) Fever 2 37.5"C 75 (37.5) 69 (35.9) Chills I(0.5) 3 (1.6) Sore throat 6 (3.0) 6 (3.1) Rash 28 (14.0) 37 (19.3) Cough 44 (22.0) 35 (18.2) Conjunctivitis 14 (7.0) 15 (7.8) Diarrhoea 49 (24.5) 32 (16.6) Vomiting 18 (9.0) 13 (6.7)

Physical signs (%) Parotid and/or

submaxirnallary swelling 4 (2.0) 3 (1.6) Cervical Lymphadenopathy 4 (2.0) 6 (3.1)

Local reactions (%) 7 (3.5) 13 (6.7)

*Chi-square test and Fisher test ns.

enteric clinical findings, were the second most common systemic reactions in both groups, with a peak incidence between day 8 and day 13 postvaccination. Parotid and/or submaxillary swelling was recorded in 2% of the children vaccinated with the UAS vaccine and in 1.6% of those vaccinated with the JLM vaccine. No significant difference with respect to systemic reactions, physical signs, and local reactions was found between the two groups of vaccine recipients.

DISCUSSION

Children (400) were vaccinated either with the mumps-measles UAS vaccine (group 1: 202 vaccine recipients) or with the JLM vaccine (group 2: 198 vaccine recipients). There was no significant difference between the two groups with regard to sex, age, and time between vaccination and serum sampling (Table I).

Children vaccinated with the UAS vaccine had a better mumps virus antibody response than the JLM vaccine recipients, not only in terms of the numbers respond- ing but also with respect to the height of the antibody response (Tables 11, 111, Fig. I). Significant differences in the seroconversion rates and in the vaccine-induced mumps virus antibody concentrations between the two vaccines in this age group have also been described by others, using the neutralization together with the haemolysis- in-gel test for the screening of the postvaccination sera [Vesikari et al, 19831. These authors report a 92.6% mumps virus antibody seroconversion rate for the UAS vaccine with a geometric mean mumps neutralization titre of 3.27 compared to a 83.5% seroconversion rate for the JLM group with a geometric mean mumps neu- tralization titre of 1.67. Even when considering a delayed mumps antibody response of the JLM vaccine recipients as proposed by these authors, the timing cannot account for the difference in the mumps antibody seroconversion rate of the two vaccines in our study, since the postvaccination serum samples of the nonresponders were drawn between day 70 and 160 postvaccination, a time when evidence of seroconversion could reasonably be expected. Others [Brunell et al, 19831 have reported a 98.3%

Evaluation of Two Mumps-Measles Vaccines 77

mumps antibody seroconversion rate after administration of the trivalent Jeryl Lynn- Edmonston-HPV 77 vaccine, using a specific OD of 0.029 as cutoff in their ELISA system. The lower seroconversion rate of mumps virus specific antibodies in our study might be due to our strictly defined cutoff level of at least 150 U (minimal specific OD of 0.17). It may well be that vaccine recipients in our study showing a seroconversion of mumps virus antibodies from 0 to 80, 100, or 130 U can also be considered to be immune to mumps. However, the fact that vaccine recipients whose prevaccination sera contained low levels of antibodies detectable by the mumps ELSA (150-200 U) had a significant antibody response after vaccination (400-900 U) seems to indicate that the presence of these low concentrations of serum antibodies does not necessarily protect from infection. Provisions for a clinical and serological follow-up of our vaccine recipients over a five-year period have been made, so that we hope to determine the lowest mumps virus specific antibody concentration provid- ing protection against the disease.

As mentioned above, in the postvaccination sera of children vaccinated with the UAS vaccine higher concentrations of mumps antibodies were found as compared to those of the JLM vaccine recipients (Table 111, Fig. 1). The significant difference in the vaccine-induced mumps virus antibody concentrations between the two vaccines has also been noted previously [Vesikari et al, 19831 and seems to indicate a higher immunogenicity of the Urabe Am 9 mumps virus vaccine strain compared to the Jeryl Lynn strain for the age group studied.

No significant difference in the seroconversion rates and in the concentrations of measles virus specific antibodies were found between the two vaccines (Tables 11, 111, Fig. 1). The measles antibody response in both groups of vaccine recipients was slightly better than that observed for mumps virus (98.5% and 96.8%, respectively) and compatible with those described by others prune11 et al, 1983, Vesikari et al, 19831. Due to the better mumps virus antibody response of the UAS vaccine recipi- ents, the seroconversion rate for both vaccine components of the double-seronegative children was significantly higher in group 1 (Table 11). In contrast to the findings of the Scandinavian group [Vesikari et al, 19831, which reported a slightly higher rate of postvaccination symptoms in the Urabe Am 9-Schwarz vaccine recipients, the frequencies of side reactions in our study were quite similar for both vaccines (Table IV) and within the range of those usually found after the application of mumps- measles vaccines in this age group [Schwarz et al, 1975; Ehrenkranz et al, 19751.

The present study shows that the immunogenicity of the measles component of both vaccines under study is similar and that the Urabe Am 9-Schwarz vaccine induces a significantly better mumps virus antibody response than the JLM vaccine in the age group studied. Long-term follow-up studies will be necessary to show whether the difference in the mumps antibody responses between the two vaccines actually reflects a difference in the protection rate against this disease.

ACKNOWLEDGMENTS

The authors thank Mrs. Ch. Rabeck, Mrs. B. Spiegel, and Mrs. H. Dippe for excellent technical assistance and Mag. U. Apfelthaler for typing the manuscript.

REFERENCES

Albrecht P, Ennis FA, Saltzman El, Krugman S (1977): Persistence of maternal antibody in infants beyond 12 months: Mechanism of measles vaccine failure. The Journal of Pediatrics 91:715-718.

78 Popow-Kraupp et a1

Bishop RF, Cipriani E, Lund JS, Barnes GL, Hosking CS (1984): Estimation of rotavirus immunoglob- ulin G antibodies in human serum samples by enzyme-linked immunosorbent assay: Expression of results as units derived from a standard curve. Journal of Clinical Microbiology 19:447-452.

Brunell APh, Weigle K, Murphy D, Shehab Z, Cobb E (1983): Antibody response following measles- mumps-rubella vaccine under conditions of costumary use. The Journal of the American Medical Association 250: 1409-1412.

Buynak EB, Hilleman MR (1966): Live attenuated mumps virus vaccine. 1 . Vaccine development. Proceedings of the Society for Experimental Biology and Medicine 123:768-775.

Chanock RM, Wong DC, Huebner RJ, Bell JA (1960): Serological response of individuals infected with parainfluenza viruses. American Journal of Public Health 50: 1858-1865.

Ehrengut W, Georges AM, AndrC FE (1983): The reactogenicity of the Urabe Am 9 live mumps vaccine and persistence of vaccine induced antibodies in healthy young children. Journal of Biological Standardization 11: 105-113.

Ehrenkranz NJ, Ventura AK, Medler EM, Jackson JE, Kenny MT (1975): Clinical evaluation of a new measles-mumps-rubella combined live virus vaccine in the Dominican republic. The Bulletin of the World Health Organization 52:81-85.

Forghani B, Schmidt NJ (1979): Antigen requirements, sensitivity, and specificity of enzyme immunoas- says for measles and rubella viral antibodies. Journal of Clinical Microbiology 9:657-664.

Henle W (1969): Mumps virus. In: Lennette EH, Schmidt NJ (eds.): Diagnostic Procedures for Viral and Rickettsia1 Diseases. New York: American Public Health Association, pp 457-480.

Isomura S, Asano Y, Hon AS, Miyala T, Suzuki S (1973): Studies on live attenuated mumps vaccine. I. Comparative field trials with two different live vaccines. Biken Journal 16:39-42.

Krugman S, Giles JP, Jacobs AM, Friedman H (1965): Studies with a further attenuated live measles virus vaccine. Pediatrics 66:471-488.

Kuno-Sakai M, Iwasaki H, Kimura M (1984): Enzyme-linked immunosorbent assay of mumps antibody for evaluation of immune status before and after vaccination. The Journal of Infectious Diseases 149: 8 13.

Lenikki PO, Shekarchi I, Tzan N, Madden DL, Sever JL (1979): Evaluation of enzyme-linked immu- nosorbent assay (ELISA) for mumps virus antibodies. Proceedings of the Society for Experimen- tal Biology and Medicine 160:363-367.

Lennette EH, Jensen FW, Guenter RW, Magoffn RL (1963): Serological response to parainfluenza viruses in patients with mumps virus infection. Journal of Laboratory and Clinical Medicine

Malvano R, Boniolo A, Dovis M, Zannino M (1982): ELISA for antibody measurement: Aspects related to data expression. Journal of Immunological Methods 4 8 3 1-60,

Meurman 0, Hanninen P, Krishna RV, Ziegler T (1982): Determination of IgG- and IgM-class antibodies to mumps virus by solid-phase enzyme immunoassay . Journal of Virological Methods

Popow-Kraupp T (198 I): Enzyme-linked immunosorbent assay (ELISA) for mumps virus antibodies. Journal of Medical Virology 8:79-88.

Popow-Kraupp T, Kunz Ch, Hofmann H (1982): Antibody response after application of a new live attenuated mumps vaccine (PariorixR) measured by enzyme-linked immunosorbent assay (ELISA). Journal of Medical Virology 10: 119-129.

Sakata H, Hishiyama M, Sugiura A (1984): Enzyme-linked immunosorbent assay compared with neutralization tests for evaluation of live mumps vaccines. Journal of Clinical Microbiology

Schwarz AJF, Jackson JE, Ehrenkranz NJ, Ventura A, Schiff GM, Walters VW (1975): Clinical evaluation of a new measles-mumps-rubella trivalent vaccine. The American Journal of Diseases of Children 129: 1408-1412.

Ukkonen P, Vaisanen 0, Penttinen K (1980): Enzyme-linked immunosorbent assay for mumps and parainfluenza type 1 immunoglobulin G and immunoglobulin M antibodies. Journal of Clinical Microbiology 1 1 :3 19-323.

Vesikari T, AndrC FE, Simoen E, Florent G, Ala-Laurila EL, Heikkinen A, Kuusinen H, Terho A (1983): Evaluation in young children of the Urabe Am 9 strain of live attenuated mumps vaccine in comparison with the Jeryl Lynn strain. Acta Paediatrica Scandinavica 72:37-40.

Vesikari T, AndrC FE, Simoen E, Florent G, Ala-Laurila EL, Heikkinen A, Kuusinen H, Terho A (1983): Comparison of the Urabe Am 9-Schwarz and Jeryl Lynn-Moraten combinations of mumps-measles vaccines in young children. Acta Paediatrica Scandinavica 72:41-46.

61~780-788.

4:249-257.

19:2 1-25.

Evaluation of Two Mumps-Measles Vaccines 79

Weibel RE, Stokes J, Buynak EB, Whitman J, Hilleman MR (1967): Live attenuated mumps virus vaccine. 3. Clinical and serologic aspects in a field evaluation. New England Journal of Medicine

Weibel RE, Villarejos VM, Hernandez CG, Stokes J, Buynak EB, Hilleman MR (1973): Combined live measles-mumps virus vaccine. Archives of Diseases in Childhood 48532-536.

Yamanishi K, Takahashi M, Ueda S , Minekawa Y, Ogino T, Suzuki N, Okuno Y, Kan I (1973): Studies on live mumps virus vaccine. V. Development of a new mumps vaccine “Am 9” by plaque cloning. Biken Journal 16: 161-166.

276:245-251.