Risk of myocarditis (heart inflammation) in men under 40 years old is higher after 2 doses of an mRNA vaccine than from SARS-CoV-2 itself, particularly after Moderna where it's many times higher: https://vinayprasadmdmph.substack.com/p/uk-now-reports-myoca...

Article is an overview of the most interesting findings; in particular I'm referencing the second image, which is copied directly from a study that's linked right above it.