Rare cases of myocarditis and pericarditis after COVID-19 mRNA vaccination have been recently reported in male adolescents and young adults. Acute myocarditis and pericarditis following COVID-19 mRNA vaccination in male adolescents and young adults may be connected with age-related lower levels of T-bet and PD-1 in predisposed individulas with T-bet polymorphisms by the release od autoreactive CD8+CTL. Upregulatiomn of T-Bet and PD-1 by estrogen might explai the higher incidence of men developing myocarditis or pericarditis in comparison to women.