Staying Fit
Most COVID-19 vaccine recipients are well-versed in the common side effects that follow shots one and two in the Pfizer and Moderna series — a sore arm, maybe a headache, perhaps some muscle pain or fatigue. But a much rarer reaction has been drumming up concern lately: myocarditis, or inflammation of the heart muscle.
Here’s what you need to know about the condition and its link to COVID-19 and the vaccines.
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1. Myocarditis has many causes
It may be the first time you’re seeing it in headlines, but myocarditis is not a new ailment. A number of things can cause it, including viral infections, certain medications, some autoimmune diseases, and exposure to environmental toxins like heavy metals and radiation. A reaction to a vaccine can also lead to myocarditis, although it’s rare, according to the National Heart, Lung and Blood Institute.
The Centers for Disease Control and Prevention (CDC) says it is “actively monitoring” reports of myocarditis and pericarditis (inflammation of the sac that surrounds the heart) in a small share of people who have received the mRNA vaccines from Pfizer and Moderna; in most cases the condition occurs after the second shot. The agency estimates there are 12.6 cases of myocarditis per million second doses of mRNA COVID-19 vaccines administered to individuals 12 to 39 years of age. A more recent study published in JAMA Internal Medicine found a rate of 5.8 cases of myocarditis per million second doses in adults.
“The other thing that's notable is that the vast majority of cases are self-resolving,” says Nisha Gilotra, M.D., an assistant professor of medicine and director of the Cardiac Sarcoidosis Program at Johns Hopkins Medicine — meaning most patients get better quickly after rest and without major medical treatment.
“In fact, [myocarditis] is probably underreported because so many of the cases can be asymptomatic or subclinical. A very rare proportion will [have symptoms that bring them into a health care setting] or be on the more severe spectrum,” Gilotra adds.
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