That's much too small. If all the participants of that study were were highest risk (18-25 males) and early COVID strains and vaccines were equally risky that s

That's much too small. If all the participants of that study were were highest risk (18-25 males) and early COVID strains and vaccines were equally risky that study should have expected to find 2-5 cases. Then there are also problems like biases toward finding myocarditis towards the end of the pandemic when there was higher awareness.