Nordic cohort study suggests that myocarditis risk slowly snowballs with more spike protein exposure

In this cohort study of 23.1 million Nordic residents aged 12 years or older, the risk of myocarditis was higher within 28 days of vaccination with both BNT162b2 and mRNA-1273 compared with being unvaccinated, and higher after the second dose of vaccine than the first dose. The risk was more pronounced after the second dose of mRNA-1273 than after the second dose of BNT162b2 [Moderna has a higher dose of active ingredient], and the risk was highest among males aged 16 to 24 years. Our data are compatible with 4 to 7 excess events within 28 days per 100 000 vaccinees after a second dose of BNT162b2, and 9 to 28 excess events within 28 days per 100 000 vaccinees after a second dose of mRNA-1273.

A different study looking at an online cohort over time found that side effects are more common after having had previous COVID. This suggests that spike protein damage is cumulative and adds up over time the more times you are exposed.