Statement from the Council of Chief Medical Officers of Health (CCMOH): Update on COVID-19 Vaccines and the Risk of Myocarditis and Pericarditis


October 1, 2021 | Ottawa, ON | Public Health Agency of Canada

We continue making great progress with COVID-19 vaccination across Canada. More than 80% of the eligible population aged 12 years and older have now been fully vaccinated. We must continue our efforts to promote vaccination to those who have not yet received their complete vaccination series, in particular for youth and younger adults, given the risks posed by the very contagious Delta variant. Vaccination continues to be one of the most effective ways to protect our families, communities, and ourselves against COVID-19, including those not eligible for vaccine, and to preserve capacity of our health systems. All vaccines authorized for use in Canada are assessed for safety, efficacy and quality by Health Canada. Over 56 million doses of a COVID-19 vaccine have been administered to date, and more than 27 million individuals in Canada are now fully vaccinated, with serious side effects remaining rare (0.008% of all doses administered).

As part of the careful monitoring of these vaccines, reports of rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart) after immunization with mRNA COVID-19 vaccines continue to be reported in Canada and around the world.

Cases of myocarditis and/or pericarditis related to vaccines occur more often in adolescents and adults under 30 years of age, more often in males than in females, more often after a second dose of an mRNA vaccine than after a first dose and most occur within seven days of vaccination. Vaccine safety surveillance data in Canada also suggest relatively higher rates of myocarditis and/or pericarditis reported after Spikevax (Moderna) vaccination compared to Comirnaty (Pfizer-BioNTech). While follow-up is ongoing, the available data indicate that the majority of affected individuals, even if hospitalized, experience relatively mild illness, respond well to conservative treatment, and recover quickly. It is also important to consider that the risk of cardiac complications, including myocarditis, has been shown to be substantially increased following SARS-CoV-2 infection, and that it is higher following infection than after vaccination.

Individuals in Canada should be assured that all COVID-19 vaccines authorized for use in Canada have been rigorously tested and carefully reviewed by Health Canada. Health Canada's independent drug authorization process is recognized around the world for its high standards and rigorous reviews. Observational studies, including those from Canada, continue to show that both approved mRNA vaccines result in high vaccine effectiveness, particularly against severe disease. Some studies suggest that Spikevax (Moderna) vaccine has higher effectiveness and/or immune response and less waning immunity compared to Comirnaty (Pfizer-BioNTech) COVID-19 vaccine.

As part of Canada's vaccine surveillance system, Health Canada, the Public Health Agency of Canada, in collaboration with Canada's provinces and territories, vaccine manufacturers, and international partners, collect, evaluate reports and publicly report suspected adverse reactions following immunization after vaccines are approved for use in Canada.

The National Advisory Committee on Immunization (NACI), in considering the rare risks and known benefits of COVID-19 vaccines, continues to recommend vaccination with either mRNA COVID-19 vaccines for people 12 years of age and over, given the proven benefits of the vaccines in preventing severe illness and death.

Provinces and territories are responsible for designing and delivering their immunization programs. Provincial and territorial governments consider NACI advice in determining the best ways to manage their immunization programs based on their unique needs and circumstances, including local epidemiology, local vaccine supply and rollout logistics, and other public health considerations. These decisions are also based on Canada's successful vaccination strategy, which includes mixed vaccination schedules. We continue to be committed to providing information to the public and health professionals to support individuals in informed decision-making on vaccination.

As Chief Medical Officers of Health, we take vaccine safety very seriously and continue to make safety a priority in the careful design of our advice and vaccine programs.

The benefits of vaccination are clear. Evidence continues to show that vaccines are effective at preventing severe illness, hospitalization and death from COVID-19, including against variants of concern. Canada's Chief Medical Officers of Health encourage all individuals to get vaccinated to protect themselves and those around them.

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.

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