CPHA Canvax

Enhancing Canada’s Vaccine Safety Surveillance for COVID-19 Vaccination Programs

Karina A. Top, Julie A. Bettinger, Jeffrey C. Kwong, Sarah E. Wilson, Sandani Hapuhennedige

Top, Karina A.1,  Bettinger, Julie A.2,  Kwong, Jeffrey C.3, Wilson, Sarah E.3,4, Hapuhennedige, Sandani5 

  1. Canadian Center for Vaccinology, Dalhousie University, IWK Health Centre 
  2. Vaccine Evaluation Center, BC Children’s Hospital Research Institute, University of British Columbia 
  3. Centre for Vaccine Preventable Diseases and Dalla Lana School of Public Health, University of Toronto, ICES, Public Health Ontario 
  4. Public Health Ontario, Dalla Lana School of Public Health, University of Toronto, ICES 
  5. Dalla Lana School of Public Health, University of Toronto

Disclosure of Conflict of Interest statement – COI: KAT has received grants from GSK and consultancy fees from Pfizer unrelated to this work. JAB: none. SEW: none. JCK: none. SH: none. 

Canada’s well-established vaccine safety surveillance system involves federal and provincial/territorial collaborations that involve both passive and active surveillance for adverse events following immunization (AEFIs). Adverse events are health events that are temporally associated with, but not necessarily causally linked to, vaccination. Through passive surveillance, AEFI reports are submitted to public health authorities, who review the reports and collect further information to assign events to surveillance case definitions. In most jurisdictions, healthcare workers are mandated to report AEFIs that meet provincial/territorial reporting criteria. Several provinces also accept AEFI reports submitted by individuals or caregivers, although this represents a minority of the reports received. At the provincial/territorial level, AEFI reports are reviewed and summarized in surveillance products; individual reports are submitted to the Public Health Agency of Canada (PHAC) as part of the Canadian Adverse Event Following Immunization Surveillance System (CAEFISS). PHAC works closely with Health Canada, which receives reports from vaccine manufacturers and has the responsibility for any regulatory actions in the event of a vaccine safety signal.

In contrast, active surveillance involves proactively searching for AEFIs in health records or eliciting symptoms and health events from individuals following vaccination. In Canada, active monitoring is currently being conducted through two programs: Immunization Monitoring Program ACTive (IMPACT), and Canadian National Vaccine Safety Network (CANVAS).The former involves 12 tertiary care pediatric hospitals (13 for COVID-19) and scrutinizes health records to detect and select AEFIs that lead to hospitalization. The second program, CANVAS, is part of the Canadian Immunization Research Network (CIRN) and relies on participant-centered reporting via web surveys to identify AEFIs that prevent daily activities or require medical attention. CANVAS has been used to rapidly gather safety data about adults and children during annual influenza vaccination campaigns.1    

Canada’s vaccine safety system is also equipped to assess and manage individuals who have experienced AEFIs via the Special Immunization Clinic (SIC) Network, another CIRN network. Through the SICs, physicians assess individuals who have experienced serious AEFIs and provide recommendations on future vaccinations.2,3 These cases are logged into a registry to assess outcomes following re-immunization; this enables further understanding of how to manage patients with similar AEFIs.2,3 SICs currently operate in eight provinces through a referral process, and until recently focused primarily on pediatric populations.

Enhancing Surveillance for COVID-19 Vaccines

As with any new vaccination program, the risks of very rare adverse events following COVID-19 vaccination (e.g., occurring in <1 per 100,000) are not fully known until the vaccines are administered to millions of individuals. In addition, the safety profile of COVID-19 vaccines in population groups not included in clinical trials (e.g., pregnant people, immunocompromised individuals) was not known at the time of Health Canada authorization and has since been informed by post-implementation safety assessments using observational data.4,5  

Recognizing these challenges, existing surveillance systems have been augmented or expanded to ensure robust safety monitoring of COVID-19 vaccination programs. After the launch of COVID-19 vaccination programs, provinces and territories supported enhanced weekly reporting of COVID-19 vaccine AEFIs to CAEFISS; enhanced surveillance continues for select AEFIs of special public health interest (e.g., myocarditis).CANVAS has also expanded its participant-centered monitoring of COVID-19 vaccinations (see https://canvas-covid.ca) through online enrollment of participants across at least seven provinces/territories. CANVAS is uniquely positioned to capture data on Canadians receiving COVID-19 vaccines. CANVAS also collects information on people who have not yet been vaccinated (i.e., a control group) to estimate the expected background rate of health events. This facilitates analysis of health outcomes and detection of safety signals with greater precision. Similar participant-focused active vaccine safety surveillance networks exist in other countries, such as the United States (via V-safe6) and Australia (via AusVaxSafety7). However, Canada is unique in its inclusion of a control group. 

The SIC Network has also scaled up by (i) adding several new clinics for adults with AEFIs following COVID-19 vaccinations and (ii) collaborating with allergy-immunology specialists in additional provinces. The SICs are also collaborating with CANVAS, as well as public health authorities, to facilitate rapid referrals; this helps to minimize delays in responding to vaccine safety concerns and managing a patient’s completion of the COVID-19 vaccination series. Harmonized protocols have been developed to manage patients with hypersensitivity reactions and myocarditis/pericarditis after COVID-19 vaccination. Additionally, the SICs are collaborating on studies evaluating vaccine safety and immune responses in immunocompromised patients who were not included in clinical trials for COVID-19 vaccines. This investment will ultimately provide guidance on how to vaccinate these populations.

Finally, CIRN’s Provincial Collaborative Network (PCN), a network that facilitates the linkage of large-scale health data (e.g. laboratory, immunization, and health administrative databases) in several provinces, is also supporting assessments of COVID-19 vaccine safety by estimating background rates of AEFIs of special public health interest and by conducting hypothesis-driven studies to confirm vaccine safety signals identified in Canada or elsewhere. Through administrative data linkage, PCN can identify population sub-groups, such as people who are pregnant or who have underlying medical conditions, to monitor these groups for vaccine safety outcomes following vaccination.

Together these enhancements to Canada’s vaccine safety monitoring systems facilitated an early response to safety concerns detected in other countries such as thrombosis with thrombocytopenia syndrome following adenoviral vector COVID-19 vaccines (e.g., AstraZeneca) and myocarditis/pericarditis following COVID-19 mRNA vaccination, allowing early recognition and prompt treatment of cases in Canada. The detection of these safety signals in Canada also led to public health action, such as a recommendation against use of adenoviral vector vaccines in individuals under 30 years of age, and eventually ending the use of that vaccine altogether as mRNA vaccine supply increased.

Building Public Confidence

Equally important to robust and enhanced vaccine safety monitoring is the thoughtful inclusion of clear vaccine safety communication strategies to ensure transparency and ideally to build public confidence. Knowledge-sharing mechanisms can include publicly accessible vaccine safety dashboards such as those updated weekly by PHAC9 and CANVAS10, as well as provincial/territorial vaccine safety surveillance reports11, 12

Beyond these communication strategies, healthcare providers (HCPs) play a large role in building public confidence, given their rapport with patients and their influence over immunization decision-making.13,14,15 HCPs can use routine visits to communicate the safety of COVID-19 vaccines, counsel patients who may have concerns, and ultimately build vaccine confidence. To do this effectively, HCPs should ;be familiar with vaccine safety surveillance systems to be able to integrate this information into discussions with patients.15,16 However, HCPs should also be aware of their critical role in ensuring the success of vaccine safety surveillance efforts by reporting AEFIs to their local public health authority. Additionally, and where possible, HCPs can inform patients/clients about CANVAS and refer patients with AEFIs to SICs when appropriate.


The evidence to date, with about 4.9 billion COVID-19 vaccine doses administered worldwide17, supports the safety of these vaccines. However, investment in vaccine safety surveillance has been critical, considering the pace of vaccination against COVID-19, the anticipated approval of other new COVID-19 vaccine products and the expansion of vaccination programs to younger age groups. There is a need for enhanced vaccine safety monitoring systems and studies among special populations to continue to build evidence on COVID-19 vaccine safety. To support vaccine acceptance, it is also important to ensure that information about COVID-19 vaccine safety is communicated clearly to both the public and healthcare providers. 


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