ImmunizationAmha Mekasha, MD, Msc

DPCH

June 2012

Session objectives

• Define types of immunity

• Describe types of vaccines

• List contraindications of vaccinations

• Identify adverse effects following immunization

• Describe cold chain in immunization

• Define some key concepts in vaccination management

Under 5 Deaths from Vaccine Preventable Under 5 Deaths from Vaccine Preventable Diseases - 2002Diseases - 2002

Others = Polio, YF, Hep.B, Jap encep, Meningococcal

Over 2 Over 2 Million Million

Deaths to Be Deaths to Be PreventedPrevented

Passive & active immunity

natural immunity artificial immunity

post- infection

active

maternal antibody

transfer to the fetus

passive

exposure to antigen

active immunisation

active

injection of antibodies

passive immunisation

passive

Passive immunisation

antibody donor(immune subject)

antibody recipient(non-immune subject)

antibody transfer

Passive immunisation

anti

bod

y co

nce

ntr

atio

n

weeks4 8 12 16 20

injection of Ig

• short-term protection

• potential safety concerns

Vaccination

antigen (vaccine)administered to non-immune subject

actively immunised subject

Active immunization

anti

bod

y co

nce

ntr

atio

n

weeks4 8 12 16 20injection of vaccine

• long-term protection

• cost-effective

• safe

• is affordable & accessible to all

• has an acceptable reactogenicity profile

• is immunogenic and protective

• provides long-lasting protection

• does not require frequent boosters

• can be integrated into EPI

• is stable in field use

The ideal vaccine ….

• reduces morbidity & mortality• is a cost-effective intervention• protection of the individual• protection of communities (herd immunity)

• control of disease• elimination of diseases• eradication of disease & the pathogen

Benefits of vaccination

Benefits of vaccination

20

40

60

1980 1990 2000

polio - worldwidere

po

rted

ca

ses

(000

s)

EPI implemented

1950 1960 1970 1980

measles - US

vaccine introduced

20

40

60

1940 1950 1960

Diphtheria – England & Wales

rep

ort

ed c

ase

s (0

00s

)

vaccine introduced

Types of vaccines

• live-attenuated vaccines– polio Sabin (OPV), measles, mumps, varicella,

yellow fever, – BCG, cholera, typhoid fever ….

• killed, inactivated vaccines– polio Salk (IPV), hepatitis A, whole cell

pertussis (Pw) ….

Types of vaccines

• sub-unit vaccines– diphtheria, tetanus, pertussis toxoids– purified acellular pertussis (Pa) components– genetically engineered HBsAg, HPV, malaria– polysaccharides (Vi, Men, Pneumo) – conjugated polysaccharides (Hib, Men, Pneumo)– split or sub-unit influenza vaccines H1N1,

H3N2 (H5NI)

Types of vaccines

• combined vaccines– DTPw-HepB (Tetra); DTPw-HepB/Hib (Penta)– DTPw-HepB/Hib-MenAC (Hepta)– DTPa-HepB-IPV/Hib– Hib-MenC; Hib-MenCY; Hib-MenAC(W?)– Men ACWY polysaccaride vaccines– MenACWY conjugate PS vaccines– HepA/Vi; HepAHepB ….

Live-attenuated vaccines

strain attenuation in cell culture

wild virus replication in unfavourable conditions

the process is repeatedmany times …

… to produce an attenuated strain, unable to cause disease

Live-attenuated vaccines

attenuated virus from the Master Working Cell Bank …

is replicated on a

large scale

then harvested, tested, and formulated into a vaccine

Live-attenuated vaccines

disadvantages• may retain some pathogenicity

• may revert to virulence

• may not be safe enough to vaccinate highly immuno-compromised subjects

• require a good cold chain

Live-attenuated vaccines

advantages

• mimic natural infection• produce a large antigenic stimulus• generally induce T&B lymphocyte responses• provide long-lasting protection

Killed, inactivated vaccines

the pathogen is grown under suitable conditions

purified and treated with heat or chemicals

… so that it is inactivated but still immunogenic

Killed, inactivated vaccines

disadvantages

• often less effective than live-attenuated vaccines

• several doses needed for long-termprotection

• repeat administration may increase reactogenicity

• limited production capacity & higher price

Sub-unit vaccines

toxoid production

inactivation

antigenic determinantscapable of inducing an immune response

toxic groups

toxin

toxoid

Sub-unit vaccines

Purified antigenic extractsacellular pertussis vaccine components

• pertussis toxoid (excreted)

• filamentous haemagglutinin (excreted)

• pertactin (69 kDa outer membrane protein)

• fimbrial antigens

polysaccharides

• T-cell independent Ags• not immunogenic in infants• do not induce an immune memory (no booster effect

Sub-unit vaccinesconjugated polysaccharide vaccines

conjugated PSs

• T-dependent Ags

• immunogenic in infants as of 6 weeks

• establish immune memory• strong booster effect

Sub-unit vaccinesrecombinant HBsAg vaccines

isolation of HBV in the 1970s

isolation of the surface antigen gene

insertion of the gene into bakers’ yeast and HBsAg expression

Sub-unit vaccines

multiplication of yeast cells in fermentors

the yeast cells produce surface antigen

isolation & purification of the surface antigen particles

Adjuvants

anti

bod

y co

nce

ntr

atio

n

weeks2 4 6 8 10vaccination

primary response in the absence of adjuvant

+ adjuvant

Methods of administration

subcutaneous intramuscular

intradermaloral

Adverse reactions

• local reactions– pain at injection site, redness

– swelling

• systemic reactions– fever, malaise ...

vaccine Reaction Onset interval

BCG Lymphadenitis, Ostities, Disseminated BCG

2-6 mos1-12 mos1-12 mos

HepB Anaphylaxis 0-1 hr

MMR Febrile seizure,ThrombocytopeniaAnaphylaxisEncephalopathy

6-12 hrs15-35 days0-1 hrs6-12 days

OPV Paralytic polio 4-30 days

Tetanus Brachial neuritisanaphylaxis

2-28 days0-1 hr

DPT Seizurehyptonic hyporesponsive episodesAnaphylaxisEncephalopathypersistent inconsolable screaming >3 hrs

0-2 days0-24 hrs0-1 hr0-2 days0-24 hrs

Contra-indications• Hypersensitivity

• Symptomatic HIV infection (BCG)

• Pregnancy (except for vaccination against neonatal tetanus)

A network of refrigerators, cold stores, freezers and cold boxes organized and maintained so that vaccines are kept at the right temperature to remain potent during orders, supplies, transportation, storage, distribution to the point of

administration to the target population.

Cold chain

Storage and distribution

live-attenuated vaccines

• vaccine (but not diluent) can be stored in a freezer or at +2°C to +8°C

• after reconstitution, use as soon as possible; discard after 6 hoursor at the end of the session

Cold chain

• some vaccines are cryostable (stable if frozen)

• some vaccines are cryolabile (unstable if frozen)

• most vaccines are thermolabile (unstable if exposed to temperatures above +2°C to +8°C)

• some vaccines are more thermostable than others (DTP > measles > OPV)

Arranging Vaccine - 1Arranging Vaccine - 1

Correct use of upright refrigerators

Unplanned Storage capacity needsUnplanned Storage capacity needs

• Never freeze BCG if the diluent and the vaccine are packed together

• Freezing causes damage to: DPT-HepB-Hib, TT, inactivated polio, HepB.

Definition of some key concepts

• Coverage: is the percentage of immunized individuals among the target population

• Drop out: The drop-out rate is a comparison of number of children who start the immunisation schedule and the number who complete it.

• Access: First contact with the regular immunization service (DPT1)

• Missed opportunities: Failure to provide all antigens to the child or woman of child bearing age for which he/she is eligible

Drop-out rate: calculation

DTP1 – DTP3 drop-out rate:

cumulative doses of DTP1 - cumulative doses of DTP3 x 100

cumulative doses of DTP1

DTP1 – Measles drop-out rate:

cumulative doses of DTP1 - cumulative doses of measles

cumulative doses of DTP1x 100

• Ensure continuous supply of vaccines• Rescheduling of cancelled clinics where possible• Reduce waiting time• Client education

– Number of doses – Dates for return– Possible side effects

• Establishing a system for defaulter tracing involving both HWs and Community members.

REDUCING DROP OUTS

Calculating vaccination coverage by antigen/vaccine

CR = CR = Doses administered for a Doses administered for a vaccinevaccine x 100 x 100

target populationtarget population

• Ensure screening at every opportunity• Ensure children/mothers have immunization cards to

make screening easier

• Give all vaccines due whenever a child presents

• Eliminate all false contraindications

Preventing Missed Opportunities

Thank you