Who is at risk?
If it’s occuring in young healthy people isn’t everyone at risk?
Or have they identified risk factors?
Most at risk are young males (~12 - 30), particularly those who are athletes. A study looking at athletes in the Big 10 (college athletes) found mycarditis in 2.3% of their athletes after COVID-19 infection. (https://jamanetwork.com/journals/jamacardiology/fullarticle/2780548)
This adds to other evidence collected thus far which has shown that incident rates for myocarditis for the vaccines is about 4,000 times lower than it is for COVID-19 infection.
I think the smart policy here would be to more closely monitor anyone who fits the profile for higher risk of vaccine-induced myocarditis and possibly avoid the second shot if they show significant clinical presentation. However, the vast majority of cases of myocarditis resolve without intervention. The individual simply rests from strenuous activity for a period and they’re fine.
These are decisions that parents should be making alongside the advice of their pediatrician. The vaccines should be available, but there will always be cases where individuals show a particular risk factor that changes that risk/benefit calculation.