The study also shows that there was practically no increase in risk for the third shot (though with a fairly wide CI), so it's possible the risk may just depend on whether someone is immunonaive or not.
The risk is given by the FDA as up to 1:14285 (males aged 12-17) for the second dose:
https://www.fda.gov/media/154869/download
However, a study from Hong Kong found an incidence of up to 1:2700 in the second dose (males aged 12-17):
https://pubmed.ncbi.nlm.nih.gov/34849657/
What we don't know is whether a vaccination would actually prevent Myocarditis in a breakthrough infection. These risks may well not be mutually exclusive. In any case, the risks are not directly comparable unless you assume 100% PCR-confirmed infection risk over six months, which is of course unrealistic.
> In any case, the risks are not directly comparable unless you assume 100% PCR-confirmed infection risk over six months, which is of course unrealistic.
I do wonder how unrealistic it is with Omicron, but maybe we'll get lucky and Omicron's less likely to cause myocarditis.
[1]: https://www.medrxiv.org/content/10.1101/2021.07.23.21260998v...