As concerns regarding mRNA vaccine-caused myocarditis skyrocket on social media and news outlets, researchers have published a study in the American Heart Association’s Circulation journal with statistics regarding the potential side effect.
Myocarditis is a condition that causes inflammation in the heart, which can weaken its ability to regularly pump blood throughout the body. It can lead to heart failure, abnormal heartbeat, and sudden death. Most cases of myocarditis are caused by viruses, but the rare heart condition has been noticed as a potential side effect of mRNA vaccines for COVID-19.
The study published in Circulation statistically analyzed cases in patients younger than 21 years old who had received an mRNA vaccine within 30 days of showing symptoms of myocarditis. Researchers found that, in general, young people who experience myocarditis as a side effect of the COVID-19 vaccine recover quickly and completely.
The Circulation study found that 90.6% of adolescent and young adult patients who experienced myocarditis after vaccination were male. In most cases, symptoms presented 2 days after vaccination. The most common symptom was chest pain, which presented in 99.3% of the patients. 18.7% of the patients had low left ventricular ejection fraction (LVEF), meaning that not enough blood was pumping out of their hearts. However, all patients with low LVEF who followed up had fully recovered with normalized function.
Another study published in the New England Journal of Medicine reported that only 2.13 in 100,000 people who received the mRNA vaccine experienced myocarditis. This is much lower than the 150 in 100,000 rate of myocarditis in unvaccinated patients infected with COVID-19 as reported by the Morbidity and Mortality Weekly Report. This means that unvaccinated people infected with COVID-19 had about 70 times greater incidence of myocarditis than any person receiving the mRNA vaccine.
The Circulation study’s first author, Dr. Dongngan T. Truong, told the American Heart Association Newsroom that the data showed that “most cases of suspected COVID-19 vaccine-related myocarditis in people younger than 21 are mild and resolve quickly.”
As the data shows that myocarditis as a side effect of COVID-19 vaccination is extremely rare (2.13 in 100,000) and that almost all of those patients recovered quickly and completely, the American Heart Association continues holding its position that COVID-19 vaccines are safe and highly effective (preventing hospitalization and death in 91% of severe infections). Dr. Donald M. Lloyd-Jones, president of the AHA, said that COVID-19 vaccines were “fundamental to saving lives, protecting our families and communities against COVID-19, and ending the pandemic,” then urging parents to vaccinate their children as soon as possible.
- American Heart Association. (2021, December 6). Young people recover quickly from rare myocarditis side effect of COVID-19 vaccine. https://newsroom.heart.org/news/young-people-recover-quickly-from-rare-myocarditis-side-effect-of-covid-19-vaccine
- Boehmer, T. K, et al. (2021, September 3). Association between COVID-19 and myocarditis using hospital-based administrative data — United States, March 2020–January 2021. Morbidity and Mortality Weekly Report. https://dx.doi.org/10.15585/mmwr.mm7035e5
- Truong, D. T, et al. (2021, December 6). Clinically suspected myocarditis temporally related to COVID-19 vaccination in adolescents and young adults. Circulation. https://doi.org/10.1161/CIRCULATIONAHA.121.056583
- Witberg, G, et al. (2021, December 2). Myocarditis after COVID-19 vaccination in a large health care organization. New England Journal of Medicine. https://doi.org/10.1056/NEJMoa2110737
Note from the Editors
This article does not offer medical advice. It is a review of statements and data offered by the American Heart Association. Consult with a doctor regarding concerns related to health effects from the COVID-19 vaccine.