Myocarditis occurred most predominantly in the various studies in young men, age 16 and 17

Dr. Philip Krause, Former FDA Deputy Chief for Vaccines: "Myocarditis occurred most predominantly in the various studies in young men, age 16 and 17 but there were increased rates, higher in men than in women going up also to much older ages although not as high as the youngest. So I don't know if it's necessarily a puberty issue because this also affected people as they got older. But that was what we saw it most frequently.
And the rates of myocarditis in these young men was quite high. In the early studies it appeared to be around 1 in 5000 vaccinees. We still don't understand why that was the case. What we luckily found was that most of these cases were mild and yet there were some cases that were not mild. There were also many cases where if once diagnosed with myocarditis that changes a young man's life because he'll probably then avoid being in sports and will still have some continued medical follow up.
We don't understand it, it's most common after the 2nd dose of vaccine. We found luckily that it did not appear to be as frequent as children got younger and it also did not appear to occur with anywhere near as high frequency with 3rd and subsequent doses of vaccine.
But it is a real finding that is associated with the vaccine. Luckily in most people when they get it not severe but certainly was enough to give us pause when we were evaluating the vaccine."