Affects Fewer Than 20 People Per 1,000,000 Vaccinations
Researchers at the Yale School of Medicine studied 23 participants who developed the heart condition after their second dose of COVID-19 vaccine to learn how it developed in these few cases. Authors say the study’s small sample size is a testament to the condition’s rarity. “We were really motivated to understand this rare vaccine-associated myocarditis to hopefully make it even more rare in the future,” said co-lead author Carrie Lucas, associate professor of immunobiology at Yale School of Medicine.
A new study may partly explain what’s driving rare cases of heart inflammation, called myocarditis, in some young people who have gotten repeat doses of the mRNA COVID-19 vaccines. After running a series of tests, Yale scientists discovered myocarditis may likely be caused by an overreaction from the body’s natural immune system — and not from antibodies induced by COVID-19 vaccines, according to the study published Friday in Science Immunology.
The CDC says cases of myocarditis most frequently occur in teens and young adult males within seven days after receiving the second dose of an mRNA vaccine. Yale researchers said their study further confirmed this as 87% of their participants were male and ages ranged from 13 to 21, with the average age falling around 16 years old.
✱ Studies show people who are unvaccinated and contract COVID-19 are still more at risk of developing myocarditis compared to vaccine-related cases, and the vaccine continues to be important in preventing severe disease and transmission.
✱While severe cases can damage the heart and cause heart failure, cases of COVID vaccine-related myocarditis have typically been mild in nature,
✱Most cases of vaccine-related myocarditis have been mild and resolved on its own.
✱But it’s still unclear why the rare cases of myocarditis are concentrated in young men. “What we need to understand in a broad way is — how is the response of that age category and that sex category different from other categories in vaccination?”