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Reported side effects following COVID-19 vaccination in Canada

This page was last updated on January 19, 2024 with data up to and including January 5, 2023.

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Adverse Event Following Immunization (AEFI)

An AEFI is any untoward medical occurrence that follows immunization. It isn’t necessarily causally related to the usage of the vaccine. The adverse event may be any:

For more information, please refer to the Council for International Organizations of Medical Sciences (CIOMS) and World Health Organization. Report of CIOMS/WHO Working group on Vaccine Pharmacovigilance.

Adverse event report

One adverse event report, which represents 1 person, may report on more than 1 symptom (that is an adverse event following immunization, or AEFI).

Serious adverse event

An event is considered serious if it:

This is based on the International Council on Harmonisation E2D Post-Approval Safety Data Management: Definitions and Standards for Expedited Reporting. See: International Council on Harmonisation.

Medically important event

An event that may not be immediately life-threatening but requires intervention to prevent 1 of the outcomes listed above and may also be considered as serious. This is based on the International Council on Harmonisation E2D Post-Approval Safety Data Management: Definitions and Standards for Expedited Reporting. See:

International Council on Harmonisation.

Adverse Events of Special Interest (AESI)

This is a pre-specified medically significant event that has the potential to be causally associated with a vaccine product. It must be carefully monitored and confirmed by further special studies.

For more information, please refer to the World Health Organization. COVID-19 Vaccines: Safety Surveillance Manual.
Safety signal

Information indicating a new and potentially causal association between a vaccine and an event that could affect health. The event is either unknown or incompletely documented. It could also indicate a new aspect of a known association. The primary purpose of vaccine post-market surveillance is to detect safety concerns, such as:

For more information, please refer to World Health Organization. COVID-19 Vaccines: Safety Surveillance Manual.
Brighton Collaboration diagnostic level of certainty

Brighton Collaboration case definitions are standardized for adverse events following immunization (AEFI). They allow AEFIs to be compared across different data sources. Clinical information on the AEFI is reviewed and categorized into 1 of 5 categories. AEFIs that meet levels 1-3 have enough information to confirm that they are a case. AEFIs that meet level 4 lack sufficient information to meet the case definition. AEFIs categorized as level 5 do not meet the case definition.

Background information on the regulatory processes

Canada’s independent drug authorization process is known around the world for its high standards and rigorous review process. Decisions are based only on scientific and medical evidence showing that the vaccines are safe and effective. The benefits must also outweigh any risks. All vaccines approved in Canada are proven safe, effective and of high quality.

The work to make sure a vaccine is safe starts before the regulatory process even begins. Exploratory, preclinical studies and clinical trials are conducted to assess the vaccine’s safety and efficacy. Evidence from these activities is submitted to Health Canada for regulatory review. Health Canada’s scientific and medical reviewers then conduct a thorough and independent review of all vaccine data. Only then is a vaccine authorized for use in Canada.

Learn more about how vaccines are approved in Canada.

Once a vaccine has been approved, it is distributed and administered, and Health Canada provides regulatory oversight for safety, quality and effectiveness.

For more information, please refer to how Health Canada regulates COVID-19 vaccines in Canada.

To learn more about each COVID-19 vaccine, please refer to the approved COVID-19 vaccines page. Health Canada regularly updates a post-authorization activity table (PAAT) for each COVID-19 vaccine and treatment. The PAAT summarizes activities since authorization, including updates to the product monographs.

Monitoring the safety of marketed vaccines in Canada

Health Canada and PHAC, along with public health authorities in the provinces and territories, actively monitor the safety of COVID-19 vaccines authorized in Canada. This is to ensure that these vaccines are safe, and that their benefits continue to outweigh the risks of the disease.

If you experience any adverse events (side effects) after being vaccinated in Canada, please report them to a healthcare provider. Vaccine monitoring begins with the collection of information from the adverse event reporting forms that are submitted.

For more information, refer to the following:

Data notes

The data presented in this report are estimates and may not accurately represent national COVID-19 vaccine adverse events following immunization for the following reasons:

  1. There may be delays in receiving reporting forms and processing reporting forms which may contribute to variations in the amount of reports presented between postings. These delays may be due to jurisdictions investigating and reviewing each adverse event before submitting the information to PHAC. There are also limitations to reporting practices such as underreporting, missing information, and differing adverse event reporting practices across jurisdictions in Canada.
  2. Each posting, we update the historical data to include any delayed reporting forms from earlier weeks.
  3. Information is collected on individuals for whom an report was submitted, not on the total number of individuals who experience an adverse event as not every adverse event is reported.
  4. New information in this report may not be comprehensive but rather represents preliminary results of data received since the last posting.
  5. Reporting jurisdictions may refer to gender as opposed to sex.
  6. Information on COVID-19 vaccine doses administered are obtained from provincial and territorial partners or their websites. More details on the number of COVID-19 vaccine doses administered, please consult the COVID-19 vaccination coverage webpage.
  7. The data presented in this report represent combined numbers from both CAEFISS and the Canada Vigilance program. Canada Vigilance receives reports directly from vaccine manufacturers, healthcare professionals and consumers. CAEFISS receives reports from regional public health authorities. Although data from these 2 surveillance systems are carefully merged together, the individual programs are subject to different reporting requirements and definitions. It is also possible that the report contains duplicate reports.
  8. Adverse events of special interest are assessed according to the Brighton Collaboration level of diagnostic certainty (if available).
  9. Please note, the adverse event and AESI numbers in Figure 4 and Table 1 may be adjusted following medical case review.
  10. For adverse events with low counts (less than 10) or incomplete data on doses administered, rates will not be provided.
  11. References to age or age group in this report reflects the person's age at the time of vaccination.
  12. Deaths are assessed according to the causality assessment of an adverse event following immunization (AEFI), user manual for the revised WHO classification
  13. If no additional vaccine product information is specified, "Pfizer-BioNTech comirnaty" and "Moderna Spikevax" refer to the original formulation alone.

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