The CDC officially reported on a potential vaccine side effect of Myocarditis on June 23rd 2021 and published an additional report on July 6th of 2021. The additional report added on to this news with an update from the Advisory Committee on Immunization Practices (ACIP). The group which seemed to be the most at risk were young adult men. “We observed 411 myocarditis or pericarditis events after any dose of either mRNA vaccine, with 33–42% in people aged 18–25 years, 58–73% in men, and 6–13% in people with a history of COVID-19 diagnosis” (H.L Wong et al. 2022).
The ACIP concluded ,however, that the benefits for all suggested age groups of the mRNA COVID-19 vaccine notably outweighed vaccination risks, such as the risks of myocarditis post-vaccination (Gargano et al. 2021). Among vaccinated people from 12 years old – 39 years old there are about 12.6 cases for every million booster recipients after the second COVID-19 booster vaccine (Hromić-Jahjefendić et al. 2023). After the second dose is when symptoms most commonly occur in cases of this side effect. Myocarditis can be joined by pericarditis as well, which is the inflammation of the pericardium, the thin tissue around the heart (Gargano et al. 2021). Adolescent boys and young men reported as being at a higher risk for myocarditis after the second dose of the vaccine is something that those who are already resistant to the vaccine may be considered to be another reason for vaccine hesitancy or resistance.
NIAID: National Institute of Allergy and Infectious Diseases