Health care practitioners are required to report all Adverse Events Following Immunization (AEFI) to Toronto Public Health under the Health Protection and Promotion Act.


An AEFI is any event or reaction that occurs after receiving a vaccine. A causal relationship does not need to be proven before reporting. Of particular interest are those of a serious nature, requiring urgent medical attention or are unusual or unexpected events.

Report an AEFI when:

  • there is a concern to the patient, caregiver or health professional
  • there is an unexpected reaction in terms of type or frequency
  • there is a severe reaction requiring hospitalization or urgent medical attention
  • it is within 30 days after administering a live vaccine (such as measles, mumps, rubella or chickenpox)
  • is up to eight weeks for immune-mediated events

Fax the completed AEFI Reporting Form (Public Health Ontario) to 416-696-3492 or email the completed form to

Note: If the form doesn’t open from the link above, download it using the download icon on the top right of the page. Use Adobe’s free Acrobat Reader software to complete and save the fillable form.

What to report
Patient unique identifier, date of birth and sex
Immunization event(s) province/territory where given, date, all vaccines given including name, manufacturer, lot number, administration site and route, as well as the number in series of vaccine doses if relevant
Adverse event(s) description, including time of first onset following immunization, duration, health care utilization, treatment and outcome
Relevant medical history underlying disease, known allergies, prior AEFI
Associated event(s) acute illness, current medication, injury, exposure to environmental toxins

See the Ministry parent information sheet on vaccine safety, June 2016

To ensure the safety of vaccines, a surveillance system is set up to monitor adverse events and unusual occurrences. All adverse events investigated by Toronto Public Health are forwarded to the province, then to Public Health Agency of Canada. Adverse events are also compared internationally. Companies that produce vaccines do not help with investigations of AEFIs, but they are aware of reports for the safety of their products.