Canadian Adverse Events Following Immunization Surveillance System (CAEFISS)

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Adverse events following immunization in Canada

Health Canada (HC) and the Public Health Agency of Canada (PHAC) share the monitoring of the safety of vaccines in Canada. Market authorization holders are required to report serious adverse events following immunization (AEFIs) to the Canada Vigilance Program (CVP) in HC.

The Canadian Adverse Events Following Immunization Surveillance System (CAEFISS) is a federal, provincial and territorial (FPT) public health post-market vaccine safety surveillance system. CAEFISS is managed by PHAC and is unique in that it includes both passive (spontaneous reports from FPTs) and active surveillance.

About the system


  • continuously monitors the safety of marketed vaccines in Canada
  • identifies increases in the frequency or severity of previously identified vaccine-related reactions
  • identifies previously unknown adverse events (PDF) following immunization that could possibly be related to a vaccine (unexpected AEFI)
  • identifies areas that require further investigation and/or research
  • provides timely information on AEFI reporting profiles for vaccines marketed in Canada that can help inform immunization-related decisions

Reporting adverse events following immunization

The following diagram depicts how AEFI reports flow from origin (vaccine recipient) to PHAC. CAEFISS includes spontaneous, enhanced and active AEFI reporting processes that are further described below.

Figure 1: Public health reporting pathway for AEFIs to CAEFISS

Abbreviations: IMPACT, Immunization Monitoring Program ACTive; HPFB, Health Products and Food Branch

Text Equivalent - Figure 1

At the top of the diagram is a circle representing the vaccine recipient. From the circle, an arrow points down to a box with the immunization provider and/or health care provider with another arrow pointing from this box down to a box with local public health units. From this box, there is an arrow pointing down to a box with Federal/Provincial/Territorial Immunization Authorities and an arrow pointing to a box with Public Health Agency of Canada (CAEFISS Database).

On the left of this flow diagram, is a red box depicting IMPACT, a paediatric hospital-based national active surveillance network, with a thick arrow pointing from here to the CAEFISS Database box and 2 thin arrows pointing from IMPACT to the Federal/Provincial/Territorial Immunization Authorities box and the Local Public Health Units. To the right of the flow diagram is a box titled Marketed Health Products Directorate Canada Vigilance Program (within Health Products and Food Branch) with a dotted line, double arrow pointing between the CAEFISS Database box and the Canada Vigilance Program box.

Submitted reports

CAEFISS reports are submitted by public health authorities in provinces and territories, who in turn receive them from local public health units. Provincial and territorial authorities also receive reports from federal authorities that provide immunization within their jurisdiction, including:

  • the RCMP
  • Indigenous Services Canada
  • Correctional Service Canada

Most of these reports are generated by nurses, physicians or pharmacists who provide immunizations or who care for individuals with AEFIs. AEFIs received by National Defence and the Canadian Armed Forces are reported directly to PHAC.

Manufacturers of all drugs, including vaccines, are required to report serious adverse events as well as unexpected adverse events to the Marketed Health Products Directorate (MHPD) Canada Vigilance Program within the Health Products and Food Branch (HPFB) of HC.

Active surveillance has been conducted since 1991 by IMPACT. IMPACT is funded by PHAC through a contract with the Canadian Paediatric Society. This contract currently includes 12 pediatric centres across Canada, representing over 90% of all pediatric tertiary care beds in the country.

IMPACT screens hospital admissions for neurologic events, such as:

  • seizures
  • encephalitis
  • thrombocytopenia
  • vaccination site abscess/cellulitis
  • acute flaccid paralysis (including Guillain-Barré syndrome and aseptic meningitis)
  • other complications that may have followed immunization

Any found to be temporally linked to immunization without clear explanation are reported as an AEFI. IMPACT reports are sent to PHAC to be entered into CAEFISS, as well as to local and provincial/territorial health officials to ensure appropriate follow-up at the individual level.

Find out how to report an adverse event following immunization.

Public health actions

The flow of AEFI reports as shown in the diagram enable specific actions to be taken at each step along the way.

AEFI management, including investigation as appropriate to determine possible cause, is usually undertaken by the reporting immunization or health care provider.

Individual public health action, such as advice regarding future immunizations, is taken at the Public Health Unit or immunization provider level.

FPT health authorities collect AEFI reports as part of ongoing evaluation of their immunization programs. At the population level, public health action related to AEFI reports could include changes in immunization program policy.

PHAC collates AEFI reports in the Canadian Adverse Event Following Immunization (CAEFI) database for purposes of signal detection analysis and reporting.

If a potential signal is identified, PHAC will work closely with HC's MHPD to discuss data extracts from CAEFISS and the CVP to enable regulatory action related to vaccines marketed in Canada.

Causality assessments

The Advisory Committee on Causality Assessment (ACCA) is part of Canada's vaccine safety surveillance system and is a critical part of vaccine safety monitoring. ACCA reviews reports of adverse events following immunization received through national surveillance. The committee determines whether an event was likely to have been causally related to a given vaccine. ACCA performs its causality assessments using a process based on a standardized procedure developed by the World Health Organization.

Causality assessment findings

COVID-19 adverse events following immunization

We update this page regularly.

Previously published vaccine safety reports

For a copy of a report that is not posted online, contact the Public Health Agency of Canada.

AEFI summaries for vaccines administered over specific time periods

Reports on specific vaccines

Reports on specific adverse events

  • Myocarditis and/or pericarditis risk after mRNA COVID-19 vaccination: A Canadian head to head comparison of BNT162b2 and mRNA-1273 vaccines. Vaccine. 2022 Jul 30;40(32):4663-4671.
  • Thrombosis with thrombocytopenia syndrome (TTS) following adenovirus vector COVID-19 vaccination in Canada. Vaccine. 2023 Oct 6:S0264-410X(23)01159-3.
  • Oculo-Respiratory Syndrome Following Influenza Vaccination: Review of Post-Marketing Surveillance through Four Influenza Seasons in Canada. CCDR 2005; Vol. 31-21:217-225 (PDF, archived)
  • Oculo-Respiratory Syndrome in Association with the Influenza Vaccine: Canada, October-November 2000 (preliminary report). CCDR 2000; Vol. 26-23:201 (PDF, archived)

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