Rare cases of myocarditis have been after Covid vaccination.
This side effect seems to occur more frequently in young men.
There have been 393 cases of myocarditis/pericarditis in people 30 and under after getting vaccinated; there have been over 300 million vaccine doses administered.
In most cases, the cardiac complication was mild and resolved on its own.
Myocarditis as a side effect has been seen with other vaccines, including smallpox.
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"Although the data is still coming in on apparent myocarditis following the COVID-19 vaccine, CDC numbers through late May estimated that 16 cases of myocarditis or pericarditis would be reported for every million second doses given to people ages 16 to 39. That works out to 0.0016%, or roughly 1 in 62,000.
By contrast, de Lemos said the best studies on college athletes put the chances of a young person getting myocarditis after COVID-19 at between 1% and 3%. That's roughly 1 in 50.
So, a young person's risk of myocarditis "is much higher if they get COVID than it is if they get vaccinated," de Lemos said."