On February 26, 2021, Health Canada authorized the AstraZeneca COVID-19 vaccine as safe and effective for use in adults 18 years of age and older in Canada. On April 12th, following a safety review, Health Canada concluded that there is a possible link between very rare blood clotting events accompanied by low platelets and the use of the AstraZeneca vaccine, having assessed the latest available international data. As a result, the AstraZeneca COVID-19 vaccine product monograph has been updated accordingly by Health Canada. Overall, Health Canada concluded that the benefits of this vaccine continue to outweigh the potential risks. This adverse event is being referred to as Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) and is estimated to occur in one in every 100,000 to one in every 250,000 people vaccinated with the AstraZeneca COVID-19 vaccine.
Based on international evidence on VITT, as well the risk of severe outcomes of COVID-19 in Canada, the National Advisory Committee on Immunization (NACI) has updated its recommendations on the use of the AstraZeneca vaccine. The recommendations have been updated based on an assessment of the risk of VITT, COVID-19 exposure risk and the benefits of the vaccine in preventing serious COVID-19 disease for various age groups. NACI has lowered the age threshold for the AstraZeneca vaccine and has provided jurisdictions with considerations that will help us determine how to achieve the greatest benefits from the use of this vaccine. There are no clear risk factors for VITT; it occurs across a range of ages. However, age is a key factor in the risk of serious complications of COVID-19.
As Canada's Chief Medical Officers of Health, we thank NACI for their thorough benefit-risk analysis and for providing an assessment framework to inform provincial/territorial and regional public health decisions on how AstraZeneca COVID-19 vaccines are best used in vaccination programs.
Given some areas of Canada are experiencing high levels of cases of COVID-19 with increasing hospitalizations and deaths, and there is the potential for surges and outbreaks of COVID-19 accelerated by variants of concern across the country, NACI advises that provinces and territories should adjust the age threshold for the use of AstraZeneca vaccine based on their local epidemiology.
In addition, the optimal use of the AstraZeneca COVID-19 vaccine in our immunization programs will also vary across jurisdictions based on current and expected vaccine supply and logistical considerations.
As individuals make informed vaccination decisions, they should consider:
- Their risk of exposure to COVID-19 and the measures they can take to reduce their risk (e.g., can they remain at home or must they go out for work, etc.);
- Their risk of severe complications from COVID-19 due to their age or underlying medical conditions; and
- The benefit of being vaccinated against COVID-19 sooner.
We continue to be committed to providing information to support individuals in informed decision-making on vaccination.
Our overall goal continues to be focused on enabling as many people as possible to be immunized as quickly as possible against COVID-19 with a safe and effective vaccine, while ensuring that high-risk populations are prioritized. All of Canada's approved COVID-19 vaccines provide a high level of protection against COVID-19. Through earlier access to vaccination, we have the opportunity to vaccinate more people faster, protect our health care system, reduce severe illness and save lives.
As Chief Medical Officers of Health, we take vaccine safety very seriously. In Canada there are mechanisms to investigate and share reports of serious adverse events following COVID-19 vaccination. We continue to make safety a priority in the careful design of our advice and vaccine programs. Health Canada, the Public Health Agency of Canada, NACI and the Council of Chief Medical Officers of Health will continue to examine and assess any safety concerns and take appropriate action. Our guidance will continue to be grounded in the latest evidence and will necessarily adapt to provide the best possible advice for everyone in Canada.
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The Council of Chief Medical Officers of Health includes the Chief Medical Officer of Health from each provincial and territorial jurisdiction, Canada's Chief Public Health Officer, the Chief Medical Advisor of Health Canada, the Chief Medical Officer of Public Health of Indigenous Services Canada, the Chief Medical Officer from the First Nations Health Authority, and ex-officio members from other federal government departments.
