From the Guidelines
The rate of myocarditis from mRNA COVID-19 vaccines is approximately 1-10 cases per 100,000 vaccinated individuals, with the highest risk observed in males aged 12-17 years, at around 62.8 cases per million after the second vaccine dose. This adverse event occurs more frequently in young males, particularly adolescents and young adults under 30 years of age, and is more common after the second dose of the vaccine 1. The risk appears highest in males aged 12-17 years and 18-24 years, with 62.8 and 50.5 cases per million following the second vaccine dose, respectively. Most cases of vaccine-associated myocarditis are mild and self-limiting, with patients typically recovering within days to weeks with conservative treatment. Some key points to consider include:
- The risk of myocarditis from COVID-19 infection itself is substantially higher than the risk from vaccination 1.
- The benefits of protection against severe COVID-19 disease outweigh the risks, with an estimated 560 fewer hospitalizations, 138 fewer ICU admissions, and 6 fewer deaths per 1,000 male individuals 12-29 years of age receiving a second dose of the COVID-19 mRNA vaccine 1.
- The exact mechanism of vaccine-associated myocarditis remains under investigation, but it is thought to result from an inflammatory immune response triggered by the vaccine. Some of the key statistics on myocarditis rates from mRNA vaccines are:
- 62.8 cases per million in males aged 12-17 years after the second vaccine dose 1.
- 50.5 cases per million in males aged 18-24 years after the second vaccine dose 1.
- 2.4 cases per million in male individuals aged >30 years after the second vaccine dose 1.
- 4.2 cases per million in female individuals aged 12-29 years after the second vaccine dose 1.
- 1.0 cases per million in female individuals aged >30 years after the second vaccine dose 1.
From the Research
Myocarditis Rates from mRNA Vaccines
- The rate of myocarditis from mRNA vaccines is approximately 12.6 cases per million doses of second-dose mRNA vaccine among individuals 12 to 39 years of age 2.
- A study found that the highest risk of myocarditis was seen in males 12-17 years of age with approximately 6 cases per 100,000 second doses 3.
- Another study reported that cases of myocarditis per 100,000 vaccine doses were higher for people aged 12-17 years (2.64) and 18-29 years (2.63) than for older age groups 4.
- The crude reporting rates for cases of myocarditis within 7 days after COVID-19 vaccination exceeded the expected rates of myocarditis across multiple age and sex strata, with the highest rates seen in adolescent males aged 12 to 15 years (70.7 per million doses of the BNT162b2 vaccine) and in adolescent males aged 16 to 17 years (105.9 per million doses of the BNT162b2 vaccine) 5.
- A cohort study found that the pooled incidence rate of myocarditis or pericarditis was highest after the second dose, at 1.71 per 100,000 person-days for BNT162b2 and 2.17 per 100,000 person-days for mRNA-1273, among men aged 18-25 years 6.
Age and Sex Factors
- Myocarditis rates were higher in males than in females, with males comprising 82% of the myocarditis cases for whom sex was reported 5.
- The risk of myocarditis was higher in younger age groups, with the highest risk seen in males 12-17 years of age 3.
- A study found that the observed-to-expected ratio was highest after the second dose among males aged 18-29 years who received the mRNA-1273 vaccine (148.32) 4.
Vaccine Type
- A study found that the risk of myocarditis was higher after the second dose of the mRNA-1273 vaccine compared to the BNT162b2 vaccine, with an excess risk of 27.80 per million doses 6.
- Another study reported that the observed-to-expected ratio was higher for those who received the mRNA-1273 vaccine compared to the BNT162b2 vaccine (1.44 vs 0.74) 4.