Vaccine pharmacovigilance


According to the 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 events following immunization and other vaccine- or immuni­zation-related issues, and to the prevention of untoward effects of the vaccine or immunization".78

Like drug pharmacovigilance, vaccine pharmacovigilance aims to detect adverse events early to trigger accurate risk assessment and appropriate response (risk-management) to the problem. This ensures the minimization of negative effects to individuals. Another goal of vaccine pharmacovigilance is to lessen the potential negative impact on immunization programmes.49

Vaccine pharmacovigilance relies on three steps:39

Detect signals that suggest that an AEFI is related to a vaccine and does not occur by chance. Spontaneous reporting by health workers through AEFI surveillance systems typically generates these safety signals. Develop hypotheses on whether there is a possible causal association between an adverse event and vaccination based on the reported signals. Test hypotheses through the use of appropriate epidemiological methods, including the study of available datasets.


In Module 1 you were introduced to the rotavirus vaccine case. Take a look at the additional information in the Rotavirus vaccine example given in this question.

What hypothesis was developed as a result of the post-licensure surveillance of RotaShield® vaccine to explain why the original clinical trial (on 10 000 vaccinees) did not detect the incidence of intussusception?


  • Pharmacovigilance authorities concluded that the original clinical trial contained too few vaccinees to detect the real incidence of such a rare adverse event. As a consequence, subsequent rotavirus vaccines were subject to clinical trials containing at least 60,000 infants. This example illustrates why signal detection, hypothesis generation and testing are vital in post-licensure pharmacovigilance of vaccines.