Male adolescents and young adults experienced a higher risk for myocarditis after receiving their second COVID-19 vaccination dose, a study published Jan. 25 in JAMA found.
Researchers used the Vaccine Adverse Event Reporting System to study reports of myocarditis, or inflammation of the heart muscle, occurring after mRNA-based COVID-19 vaccination between December 2020 and August 2021 in over 192.4 million individuals older than 12 in the U.S.
Noted limitations to the study included potential for myocarditis reports to be incomplete in the passive recording system and potential for incomplete vaccine administration information.
Key findings:
- There were 1,991 reports of myocarditis to the system, and 1,626 of these reports met the case definition of myocarditis.
- Of those with myocarditis, the median age was 21 years old and the median time for symptom onset was 2 days.
- Males comprised 82 percent of the myocarditis cases in which sex was reported.
- The rates of myocarditis were highest after the second vaccination dose in adolescent males ages 12 to 15 years, in adolescent males ages 16 to 17 years and in young men ages 18 to 24 years.