Understanding the Rare Side Effects of Myocarditis and Pericarditis of COVID-19 Vaccines

After receiving some questions about the COVID-19 vaccines and the rare side effects of myocarditis and pericarditis, we decided to provide an informed update regarding these concerns. As of September 24, 2021, with 56 million COVID-19 vaccine doses given, there have been 812 reported cases of myocarditis and/or pericarditis in Canada.

What is myocarditis and pericarditis?

Myocarditis is the inflammation of the heart muscle whereas pericarditis is the inflammation of the lining surrounding the heart. Most of the reported cases are affecting young males under the age of 30. For those affected, symptoms typically begin within one week after vaccination and may appear as chest pain, a rapid heartbeat, and shortness of breath. Nonetheless, most of the cases were mild and improved quickly with appropriate treatment and rest.

Although rare, there have been more cases of these side effects with the Moderna vaccine than the Pfizer-BioNTech vaccine and even less with the AstraZeneca vaccine. In Ontario, as an additional precautionary measure, the following suggestion has been made: For individuals between the ages of 18-24, the Pfizer-BioNTech vaccine is the preferred vaccine over Moderna.

The National Advisory Committee on Immunization (NACI) currently recommends that individuals who experienced myocarditis and/or pericarditis after the first dose are advised to discuss second dose options including timing with their care provider.

As per the latest recommendations, the benefits of vaccinations continue to greatly outweigh the risks. Therefore, all eligible individuals are still strongly encouraged to get vaccinated at the earliest possible time.

Kunal Bhatt, RPh, PharmD, HBSc is a staff pharmacist for Charlton Health. As a 2020 PharmD graduate from the University of Toronto, Kunal possesses a diverse range of experiences from working in hospital and community pharmacy settings. Since January 2021, Kunal was heavily invested in contributing to the efforts against COVID-19 by administering upwards of 5000 COVID-19 vaccines at William Osler Health System’s vaccination clinics.

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