Vaccine Safety

Vaccine safety surveillance is essential to the success of immunization programs.

PHO leads the provincial surveillance of adverse events following immunization (AEFIs). An 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.

In Ontario, health professionals are required to report AEFIs to their local public health unit. Public health units investigate AEFIs and provide support to immunizers, individuals, and their families.

If you experience an adverse event after immunization, please contact your health care provider.

For information specific to COVID-19, please visit the COVID-19 Vaccine webpage.

Vaccine Safety Net logo

Public Health Ontario is a member of Vaccine Safety Net – a global network of websites, evaluated by the World Health Organization, that provides reliable information on vaccine safety.

How to Report an AEFI

  1. Complete an AEFI Reporting Form
  2. Send it to your local public health unit

See our AEFI Reporting Fact Sheet for more information.

Having trouble opening PDF forms? Download and save the form directly onto your device.

Vaccine Safety in Ontario, 2019

Ongoing surveillance of adverse events following immunization (AEFI) is essential for monitoring vaccine safety and maintaining confidence in immunization programs. The following resources provide a summary of AEFIs reported in Ontario following vaccines administered in 2019, as well as trends comparing AEFIs reported across eight years between 2012 and 2019.

Vaccine Safety Surveillance Tool


Past Surveillance Reports and Supporting Resources



PHO Rounds: Updates on Influenza, COVID-19, and RSV for the 2023-24 Season

 This session will provide an overview of respiratory virus activity in Ontario and Canada during the 2022-23 season and the southern hemisphere’s 2023 season.

See the Event Details

To obtain or inquire about an immunization record, or for general immunization information, please contact your local public health unit.

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Immunization and Emergency Preparedness

Updated 29 Nov 2021