COVID-19 Infection More Likely to Inflame Heart Than Vaccine

By Jonathan Springston, Editor, Relias Media

After analyzing the data of millions of people, researchers have determined patients are more likely to experience myocarditis after contracting COVID-19 than in the weeks after receiving the vaccine.

Investigators combed through England’s national immunization database to scrutinize the information of more than 40 million patients age 13 years or older who had received at least one dose of a COVID-19 vaccine between Dec. 1, 2020, and Dec. 15, 2021. More than 21 million people had received three doses of the vaccine. Almost 6 million tested positive for COVID-19 before or after receiving a vaccine. During the study period, 2,861 people were hospitalized or died with myocarditis.

Patients infected with the virus before receiving a vaccine were 11 times more likely to develop myocarditis within 28 days of testing positive. That risk declined by half if a patient tested positive for SARS-CoV-2 after receiving at least one dose of a vaccine.

For men younger than age 40 years, the researchers reported an estimated four additional cases of myocarditis associated with the first dose of Pfizer's vaccine and 14 extra episodes with the first dose of Moderna's solution for every 1 million men vaccinated. The authors noted this risk increased with the second dose for all three vaccines studied. The risk was highest for the Moderna shot; there were 97 more myocarditis cases per 1 million. For unvaccinated men younger than age 40 years who had contracted COVID-19, there were 16 additional myocarditis cases per 1 million.

"It is important for the public to understand that myocarditis is rare, and the risk of developing myocarditis after a COVID-19 vaccine is also rare," said study co-author Nicholas Mills, chair of cardiology at the University of Edinburgh in Scotland. "This risk should be balanced against the benefits of the COVID-19 vaccines in preventing severe COVID-19 infection. It is also crucial to understand who is at a higher risk for myocarditis and which vaccine type is associated with increased myocarditis risk."

For more on this and related subjects, be sure to read the latest issues of Clinical Cardiology Alert.