2. INTRODUCTION TO VACCINE
Vaccine play a pivotal role in modern health care delivery.
WHO has defined ''Vaccine is a complex biological preparation which function by
inducing the immune system of body' 'to elicit an immune response to a particular
pathogen.
A vaccine is a typically contains an agent that resembles a disease causing
microorganism and is often made from weakened or killed forms of the microbe ,its
toxin,or one of its surface protein.
Vaccination is the process of administering of antigenic material to stimulate an
individual's immune system to develop adaptive immunity to a pathogen.
It is one of the effective way to prevent a disease.
Over the year vaccination has prevented many serious illness ,disabilities and saves
millions of life across the world.
3. DEFINITION OF VACCINE
PHARMACOVIGILANCE
Though vaccines are the best defense we have against infectious disease but no vaccine is actually
100% safe or effective for everyone because each person's body reacts to vaccines differently.
Vaccines are however not risk free and adverse effects will occasionally occur following vaccination.
To ensure the continued success of vaccine ,it's crucial to make sure that vaccines are safe
According to CIOMS WHO Working Group on Vaccine
pharmacovigilance Vaccine Pharmacovigilance is defined as
'the science and activities relating to the'
Detection
Assessment
Understanding and
Communication
Of adverse event following immunization and other vaccine or immunization related issues and to
prevention of untoward effects of vaccine or immunization.
4. OBJECTIVES OF VACCINE SAFETY SURVEILLANCE/
VACCINE PHARMACOVIGILANCE
To detect and identify problems with vaccines, which could be due to their inherent properties or
quality defects in the vaccines.
To detect correct and prevent immunization errors caused by errors in vaccine preparation ,handling
,storage or administration.
To identify signals of unknown vaccine reaction, generate new hypothesis about vaccine reactions
that are specific to a given population.
To reduce the incidence of injection reactions caused by pain or anxiety associated with
immunization by educating and reassuring vaccines, parents/guardian and the general public about
vaccine safety.
Prevent false blame from coincidental events.
5. ELEMENTS TO CONSIDER WHEN CONDUCTING VACCINE
PHARMACOVIGILANCE
Vaccine usually administered to healthy people.
Vaccine may be administered to birth cohort or to groups at high risk for disease complication.
Subpopulation may be more susceptible for certain AEFI.
The age at the time of immunization may coincide with the emergence of some age related disease.
Immunization with certain vaccine is mandate in some countries.
Benefit of immunization may not be immediately visible particularly if target disease incidence is low.
Appropriate method are needed to detect and assess any potential association of serious, rare, delayed
adverse event.
Vaccine are often administered coincidentally with other vaccine making casual attribution to a specific
vaccine difficult.
Vaccine are complex biological products may include antigen ,live organism, adjuvants, preservative .Each
component may have unique safety implication.
Consideration of dechallange and rechallange differ for vaccine compared to other medicine.
Effective communication regarding safety of vaccine and immunization is challenging.Despite strong
evidence that a serious adverse event is not related to immunization perception of harm may persist & may
potentially impact negatively on immunization of the population .
6. STEPS OF VACCINE
PHARMACOVIGILANCE
Vaccine pharmacovigilance relies on three steps-
1. Signal Detection- detects signal that suggests that an adverse event following immunization is related to
a vaccine and does not occur by chance. Spontaneous reporting by health workers through AEFI
surveillance system typically generate these safety signals.
2. Development of causality hypothesis- develop hypothesis where there is a possible causal association
between an adverse event and vaccination based on reported signals.
3. Testing of causality hypothesis- test hypothesis through the use of epidemiological methods including
study of available datasheets.
8. DETECTION AND REPORTING
Parents of immunized infants/children, healthy workers at immunization facilities and staff of accident and
emergency rooms in hospitals are most likely to recognize or detect AEFIs when they first occur.
Health workers have the responsibility to detect AEFIs and report when appropriate.
All immunization staff must be able to identify and report adverse events.
Detection requires effective staff training and education to ensure accurate diagnosis of AEFI based on clear
case definitions, which can be included on the AEFI reporting form and in the national AEFI guidelines.
9. CONDUCTING AN AEFI
INVESTIGATION
The purpose of AEFI investigation is to-
Confirm the diagnosis and determine the outcome of adverse event.
Identify specifications of implicated vaccine used to immunize patient.
Examine operational aspects of immunization programme which may have led to immunization errors.
Justify the search for AEFI cases/clustering.
Compare background risk of adverse event (occuring in unimmunized people) to the reported rate in
vaccinated population.
10. CAUSALITY ASSESSMENT OF AEFI
Causality assessment is the systematic review of data about an adverse event following immunization case.
It determine the likelihood of a causal association between event and vaccine received.
Causality assessment outcomes help raise awareness to vaccine associated risk among healthcare workers.
The quality of causality assessment depends on the-
Quality of AEFI case report.
Effectiveness of AEFI reporting system.
Quality of causality review process.
11. RISK/BENEFIT ASSESSMENT
Continuous evaluation of risk and benefits of vaccines is required to strengthen the confidence in
immunization programmes.
A risk/benefit assessment include-
Address the population at risk.
Take into account contextual issues( economics, availability of vaccines, sociopolitical and cultural factors).
Be prompted by a newly identified risk, but must remain holistic( e.g. take into account the entire safety
profile of a vaccine not only the specific information relating to event that was detected.
