Study: Myocarditis Following Second COVID-19 Vaccine Dose Rare, Should Not Discourage Vaccination


A retrospective case series published in JAMA Cardiology found that although there are rare instances of myocarditis—inflammation of the heart muscle—in younger men following COVID-19 vaccination, the greater risk for heart damage and death comes from COVID-19 infection. Although several recent studies have suggested hypersensitivity myocarditis is a rare adverse reaction to COVID-19 vaccination that health care professionals should monitor, the investigators stress that overall confidence in vaccination should not be affected by this.

The study reviewed 23 men in the US military hospitalized with myocarditis symptoms between January and April 2021 within 4 days of being given the second dose of a messenger RNA COVID-19 vaccine. Three patients had previously been infected with COVID-19, and their symptoms arose after the initial dose. However, the researchers stress that these 23 cases should be contextualized by the military’s administration of more than 2.8 million doses of messenger RNA COVID-19 vaccines at that time.

“People of all ages should choose to get a COVID-19 vaccine because the risks are extremely low compared to the benefits,” said Leslie Cooper, MD, chair of the Department of Cardiology at Mayo Clinic in Florida, in a press release. “Additionally, the growing body of research shows that vaccine-associated myocarditis resolves quickly in almost all cases.”

A second observational case study reviewed by the investigators followed 8 men between 21 and 56 years of age hospitalized with chest pain within 2 to 4 days of receiving their second dose of a COVID-19 vaccine and who were diagnosed with myocarditis by laboratory and cardiac MRI. One patient had previously recovered from COVID-19, and symptoms began after the first dose.

All 8 patients recovered from the effects of myocarditis and no longer suffered from chest pain at the time of review.

“Hypersensitivity myocarditis following vaccination is rare, with the exception of smallpox vaccine,” Cooper said in the release. “The risk of myocarditis after receiving mRNA vaccine is far less than the risk of myocarditis following actual COVID-19 infection.”


Reported cases of myocarditis in younger men following COVID-19 vaccination are rare; vaccination remains important [news release]. EurekAlert; June 29, 2021. Accessed June 30, 2021.

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