Myocarditis Risk Is 17 Times Higher for Unvaccinated Patients Who Get COVID-19

New study results show that there are more incidences of this inflammation of the heart muscle related to not being vaccinated than there are to the vaccine itself.

The 30-day incidence of myocarditis following a COVID-19 diagnosis was nearly 17 times higher than the incidence among patients receiving the COVID-19 vaccine, new data show.

That stands in contrast to recent reports indicating that adolescents and young adults, particularly males ages 12 to 29, who receive an mRNA COVID-19 vaccine have an increased risk of myocarditis, which is an inflammation of the heart muscle.

In October 2021, the FDA delayed the authorization of the Moderna COVID-19 vaccine for adolescents because of these concerns.

The results of previous studies by Epic Research show that the risk of myocarditis following the COVID-19 vaccine was not substantively different from the incidence before the COVID-19 pandemic.

In this study, Epic Research aimed to determine the risk of myocarditis among individuals aged 12 to 30 years across 3 age, sex, and vaccine type.

To determine the risk, investigators examined historical incidence, risk after vaccination, and risk after a COVID-19 diagnosis.

Historical incidence was determined by the annual incidence of individuals aged 12 to 30 who had an interaction with the health system in 2019. The historical incidence was used as a baseline to put the risk after vaccination and risk after COVID-19 diagnosis into perspective, but investigators said that it should not be directly compared with the other 30-day risks.

For risk after vaccination, investigators viewed the 30-day incidence of a new myocarditis diagnosis after the first or second vaccination against COVID-19 among individuals aged 12 to 30 years who received at least 1 vaccination dose between December 11, 2020, and December 20, 2021.

The risk after a COVID-19 infection was defined as the 30-day incidence of a new diagnosis of myocarditis following a diagnosis of COVID-19 among individuals aged 12 to 30 years who did not receive a COVID-19 vaccine between January 20, 2020, and November 21, 2021.

Investigators found that the risk of myocardia following a COVID-19 diagnosis is much higher than the risk of myocarditis following a COVID-19 vaccination for all ages and sex studied.

Overall, the 30-day incidence following a COVID-19 diagnosis was nearly 17 times higher than the incidence among individuals receiving the COVID-19 vaccine.

The historical incidence of myocarditis was 11.7 cases per 100,000 individuals.

Investigators also broke down the risk of myocarditis by sex and found that their data were consistent with other reports showing that adolescent and young adult males have a higher risk than females.

Additionally, the investigators also analyzed the risk based on vaccine manufacturer.

The Pfizer-BioNtech vaccine was the only one evaluated for the 12- to 17-years-old age group, as it was the only vaccine authorized for that age group during the study period.

For the 18-to-30-year-old age group, which had all 3 vaccines authorized for use, incidents of myocarditis were similar across vaccine manufacturers.

The results of the analysis show that the 30-day risk of myocarditis was less than the 1-year historical incidence across all 3 vaccine manufacturers when both age and sex were considered.

When evaluating the combinations of age, gender, and manufacturer, 73 cases of myocarditis was reported of 364,249 male individuals who received the Moderna vaccine, making it about 20 cases per 100,000 individuals.

This is significantly higher than other combinations age, sex, and manufacturer. However, the risk of myocarditis after vaccination remains significantly less than the risk after a COVID-19 infection.

Reference

Little D, MacGibbon A, Allen S, Posner X, and Keogh T. Myocarditis risk 17 times higher for unvaccinated patients ages 12-30 who get COVID-19 than COVID-vaccinated patients. Epic Research. January 24, 2022. Accessed January 24, 2022. https://epicresearch.org/articles/myocarditis-risk-17-times-higher-for-unvaccinated-patients-ages-12-30-who-get-covid-19-than-covid-vaccinated-patients