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An adverse event following immunization (AEFI) is any untoward medical occurrence in a vaccine that follows immunization. It does not necessarily have a causal relationship with the vaccine or the immunization process.
- On This Page
- Introduction
- Adverse Events Following Immunization (AEFI) Definitions
- When and How to Report An AEFI
- Investigating and Managing AEFI
- Proof of Causal Association
- Individual Case Causality Assessment of AEFI
- Selected References
Evidence regarding vaccine safety generated throughout the vaccine life cycle helps to inform the risk-benefit discussion between immunization providers and potential vaccine recipients or their caregivers. Knowing about proven vaccine associations helps healthcare providers to assess clients who present with an illness in the post-immunization int...
The definitions below align with those used by the Canadian Adverse Events Following Immunization Surveillance System (CAEFISS). AEFI general definition: any untoward medical occurrence which follows administration of an active immunizing agent and which does not necessarily have a causal relationship with the use of a vaccine. The adverse event ma...
Timely AEFI reporting is essential to detect possible changes to the safety profile of all vaccines. The key criteria for reporting an AEFI are temporal association and has no other clear cause at the time of reporting. A causal relationship does not need to be proven. Vaccine providers contribute to vaccine safety by reporting AEFI which allows fu...
It is important to use standard case definitions for AEFI investigation and reporting. The Canadian Adverse Event Following Immunization Surveillance System (CAEFISS) AEFI report form has been structured to facilitate establishing whether or not reported events meet standard case definitions for AEFIs considered to be of special public health impor...
The goal of adverse event investigation and reporting is to determine whether these events are associated with the vaccine or immunization. Vaccine attributable risk is defined as the difference between the frequency of the event in the vaccinated compared to the unvaccinated population. Determination of vaccine attributable risk is primarily done ...
It is nearly impossible to assess causality without a thorough investigation, near to the time an event occurs. This is especially important for serious as well as unexpected AEFI, and it underscores the important role that immunization and other healthcare providers have in managing AEFI. The WHO guidelines for individual case assessment are an im...
De Serres G. et al. Importance of attributing risk in monitoring adverse events after immunization: hepatitis B vaccination in children. Am J Public Health 2001;91(2): 313-15.Health Canada. Canada Vigilance Program. Dated 2022-06-1. Accessed December 23, 2022: https://www.canada.ca/en/health-canada/services/drugs-health-products/medeffect-canada/canada-vigilance-program...ICH Expert Working Group. International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use. Post-approval safety data management: Definitions an...Peltola H, Heinonen OP. Frequency of true adverse reactions to measles-mumps-rubella vaccine.Lancet 1986;1(8487): 939-42.An adverse event is an untoward event that occurs after a vaccination that might be caused by the vaccine product or vaccination process. These events range from common, minor, local reactions to rare, severe, allergic reactions (e.g., anaphylaxis).
Medical Management of Vaccine Reactions in Adults in a Community Setting. The table below describes steps to take if an adverse reaction occurs following vaccination. Administering any medication, including vaccines, has the potential to cause an adverse reaction.
Psychological fright and syncope (fainting) All vaccines have the potential to cause an adverse reaction. In order to minimize adverse reactions, patients should be carefully screened for precautions and contraindications before vaccine is administered. Even with careful screening, reactions may occur.
When adverse reactions do occur, they can range from minor (e.g., soreness, itching) to serious (e.g., anaphylaxis). Be prepared. Vaccinators should know how to recognize allergic reactions, including anaphylaxis. Have a plan and supplies ready to provide appropriate medical care if an event occurs. Medical Management of Vaccine Reactions in Adults
All vaccines have the potential to cause an adverse reaction. In order to minimize adverse reactions, patients should be carefully screened for precautions and contraindications before vaccine is administered. Even with careful screening, reactions may occur.
