Vaccine Safety

Vaccines are held to the highest standards of safety. Before they are approved for use in Canada, they must be shown through multiple clinical studies to be not only effective in preventing disease but also safe to use. Canada’s long-standing vaccine safety system ensures that vaccines marketed and used in Canada are as safe as possible. Health authorities in Canada take vaccine safety very seriously.

Vaccines undergo a series of testing before they are approved for use. Most common adverse events associated with a vaccine are identified in studies before the vaccine is licensed, but rare adverse events may not be detected in these studies. Therefore, the Canadian vaccine safety system continuously monitors for possible adverse events after a vaccine is licensed. When millions of people receive a vaccine, less common adverse events that were not identified earlier may emerge.

If a link is found between a possible adverse event and a vaccine, public health officials take appropriate actions. These include determining if the recommendation for using the vaccine should change.

Although vaccines, like any medication, can have associated adverse events, not immunizing also involves risk. Not immunizing puts oneself and others who come into contact with him or her at risk of contracting diseases vaccines are meant to prevent, which can be serious, or even deadly. Even though many of these diseases have become rare in this country (thanks in large part to vaccines), they still commonly occur elsewhere around the world and can be brought into Canada, putting unvaccinated individuals at risk.

Video © 2018 Government of Canada

Adverse Events Following Immunization

An Adverse Event Following Immunization (AEFI) is any untoward medical occurrence in a vaccinee that follows immunization. It may be any unfavourable and/or unintended sign, abnormal laboratory finding, symptom or disease. The vaccine or its administration may not necessarily have been the cause.

The Public Health Agency of Canada’s (PHAC) Canadian Adverse Events Following Immunization Surveillance System (CAEFISS) monitors AEFIs from across the country through local public health units. The surveillance system seeks to ensure the continued safety of vaccines in the Canadian market.

The most common AEFIs are mild, such as redness and swelling where the shot was given, and go away within a few days. If your child experiences a reaction at the injection site, you can use a cool, wet cloth to reduce redness, soreness, and swelling.

Serious AEFIs, such as severe allergic reaction, are very rare, and doctors and clinic staff are trained to deal with them. After vaccination, if you observe any reaction that concerns you, consult a health care professional.

How AEFIs are monitored

In Manitoba, AEFI reports are received at the health regions from multiple sources: physicians, nurses, pharmacists and public health. In addition, reports are also received from a pediatric hospital-based surveillance system known as the Immunization Monitoring Program ACTive (IMPACT).

Recommendations are made by the regional Medical Officer of Health, who conveys it to the vaccine recipient’s immunization provider. The data are shared with Manitoba Health, Seniors and Active Living (MHSAL), which reviews them before forwarding to PHAC. MHSAL may, in coordination with the concerned RHA and in consultation with other local experts as well as with PHAC, perform any further investigation that may be required.

Personnel in PHAC’s Vaccine Safety Section screen all submitted reports, ensure they are entered into the CAEFISS database and coded using standard international coding terminology. Reports are monitored with special attention to serious or unusual events that could signal a concern regarding vaccine safety.

This reporting process is illustrated below:

AEFI Reporting Flow


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