A higher-than-usual number of cases of a type of heart inflammation has been reported following Covid-19 vaccination, especially among young men following their second dose of an mRNA vaccine, the CDC said Thursday. Overall, 226 cases of myocarditis or pericarditis after vaccination in people younger than age 30 have been confirmed … Further investigation is needed, however, to confirm whether the vaccination was the cause of the heart problem. Normally, fewer than 100 cases would be expected for this age group.