Adverse Events Following Immunization

An adverse event following immunization (AEFI) is an unwanted or unexpected health effect that happens after someone receives a vaccine, which may or may not be caused by the vaccine. Health care providers (i.e., physicians, nurses and pharmacists) are required by law to report AEFIs.

Reports of adverse reactions occurring in the Thunder Bay District should be made using the Ontario AEFI Reporting Form (PDF) (note: this document has shown to be difficult opening in Firefox and potentially other browsers. Please try opening the link in a different browser if you are having issues) and faxed to the Vaccine Preventable Disease department of the Thunder Bay District Health Unit at (807) 625-4828. You can also email the AEFI Reporting Form to either or


For Further Information

Contact the Vaccine Preventable Diseases Program at (807) 625-5900.

Public Health Ontario: Vaccine Safety

Last Updated: 25/04/2022