Myocarditis can be a side effect of the Pfizer and Moderna mRNA vaccines, but studies show that rare heart complications are more likely to occur as a result of coronavirus infections than as a vaccine side effect. In fact, coronavirus patients have 16 times the risk for developing myocarditis, compared to people who are uninfected, according to CDC data released in September.

The Food and Drug Administration authorized booster shots of Pfizer-BioNTech’s coronavirus vaccines for 16- and 17-year-olds on Dec. 9, after analyzing data that shows a link between myocarditis and the mRNA vaccines for male adolescents and young men.

Harlan Krumholz, a cardiologist at the Yale School of Medicine, said that in addition to the vaccines being highly effective at preventing coronavirus infections, they also provide protection from illnesses linked to the virus, including myocarditis.“These are highly effective vaccines in preventing covid itself, and that provides a lot of offsetting benefits,” Krumholz said.