Every medical intervention comes with both benefits and risks. For vaccinations, the benefits generally outweigh any potential risks for most people.
The new COVID-19 vaccines based on mRNA technology are no exception. However, one risk associated with them—particularly for young men—has raised concerns among the public.
A recent study has found that the risk of developing myocarditis—inflammation of the heart muscle, often triggered by the immune system’s response to an infection—shortly after receiving the COVID-19 vaccine is lower than the risk that can arise from contracting the disease itself.
Researchers led by Dr. Mahmoud Zureik, professor of epidemiology and public health at the University of Versailles, studied individuals aged 12 to 49 who had been hospitalized with myocarditis in France from December 2020 to June 2022, a period during which mass vaccination campaigns were underway. They categorized individuals into three groups: those who developed myocarditis and were hospitalized within seven days of receiving an mRNA shot, those admitted to the hospital within 30 days of contracting COVID-19 but had not received an mRNA vaccine in the prior seven days, and individuals with myocarditis attributed to other causes. All participants were followed for 18 months.
During this period, individuals with vaccine-related myocarditis were half as likely to be readmitted to the hospital for myocarditis or heart-related events compared to those with infection-related myocarditis or individuals with myocarditis due to other causes.
These findings suggest that the risk of myocarditis associated with the mRNA vaccines “is very, very low,” according to Dr. Zureik. It’s crucial to remember that the risk of COVID-19 to the heart “is not limited to myocarditis. There are other cardiovascular risks as well.”
These results are timely, as COVID-19 cases and hospitalizations continue to rise in the U.S. These increases are partly due to new variants and waning immunity from previous vaccines, which targeted different versions of SARS-CoV-2. Consequently, the U.S. Food and Drug Administration recently updated the COVID-19 vaccine to address the currently circulating variants. However, uptake of recent vaccine doses has been low.
The study did not delve into the reasons behind the slight link between the vaccines and myocarditis, or why the immune system’s response to the vaccine appears different from that generated by a COVID-19 infection. Dr. Zureik suggests that individuals hospitalized for myocarditis after vaccination might experience milder cases due to awareness of the potential risk.
Further research is required to gain a more comprehensive understanding of how the mRNA vaccines interact with the body’s immune system. Nevertheless, these findings provide some reassurance that the vaccines do not seem to be associated with a significantly increased risk of heart inflammation, even months after immunization.