Last updated on December 8th, 2025 at 01:42 pm

One of the few adverse events associated with the COVID vaccine has been an increased risk of myocarditis, a rare and temporary inflammation of the heart muscle. A new study has been published that examines the risk of myocarditis after receiving a COVID vaccine and after a COVID infection.

Not to give away the story I am about to write, but patients who receive the mRNA COVID vaccine and develop myocarditis show a lower frequency of cardiovascular complications than those who had post-COVID infection myocarditis.

This post will review the new research and show that the risks of COVID itself for myocarditis is much greater and worse than from the COVID vaccine.

What is myocarditis?

Myocarditis, also known as inflammatory cardiomyopathy, is a rare inflammation of the heart muscle. Symptoms may include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The duration of the condition can vary from hours to months. Complications of myocarditis may include heart failure due to dilated cardiomyopathy or cardiac arrest.

Most of the time, myocarditis is caused by an infection that reaches the heart. When it does, the immune cells that fight the infection enter the heart. These immune cells produce biochemicals that can damage the heart muscle. Consequently, the heart itself can become thick, swollen, and weak.

Many of the cases are caused by a virus that reaches the heart. These include influenza (flu), coxsackievirus, cytomegalovirus, and adenovirus. The condition may also be caused by bacterial infections such as Lyme disease, streptococcus, mycoplasma, and chlamydia.

As you can see, infectious pathogens, such as viruses and bacteria, are almost always implicated in the etiology of myocarditis. And remember, all of the COVID-19 vaccines do not contain live SARS-CoV-2 virus, they only have a piece of code for the spike protein of the virus.

In most cases, the effects are temporary, and the condition resolves itself within a few weeks or days. In general, it does not kill or permanently harm those who develop myocarditis.

There is solid evidence that COVID mRNA vaccines that were developed by Pfizer-BioNTech and Moderna slightly increase the risk of developing myocarditis, especially in young men who have received two or more doses of the vaccines. However, the risk is very small, approximately 2 per 100,000 doses of the vaccine. On the other hand, the risk of myocarditis after hospitalization with COVID is approximately 226 per 100,000 cases. In other words, the risk of myocarditis is over 110X worse after COVID infection compared to COVID vaccination.

The CDC provides clinical recommendations for physicians to manage and treat rare incidences of myocarditis and pericarditis (a related inflammation of the pericardial sac that surrounds the heart) post-COVID vaccination

COVID vaccine and myocarditis risk paper

In a paper published on 26 August 2024 in JAMA, Mahmoud Zureik, professor of epidemiology and public health at the University of Versailles, France, and colleagues used the French National Health Data System database to review all individuals, ages 12-49 years, who were hospitalized for myocarditis between Dec. 27, 2020, and June 30, 2022.

These were 4,635 people included in the cohort: 12% with post-vaccine myocarditis (within 7 days after receiving the COVID mRNA vaccine), 6% post-COVID myocarditis (within 30 days of SARS-CoV-2 infection), and 82% with conventional (unrelated to COVID infection or vaccine) myocarditis.

Here are the key results of their research:

• With 18-month follow-ups of people hospitalized for myocarditis during the COVID-19 pandemic, it appeared that composite clinical outcomes were more favorable if people had developed myocarditis soon after COVID-19 mRNA vaccination rather than conventional myocarditis.
• Importantly, the risk of poor composite outcomes — counting hospital readmission for myopericarditis, other cardiovascular events, and all-cause death — was comparable between post-COVID-19 myocarditis and conventional myocarditis groups.
• 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 COVID infection-related myocarditis or people with conventional myocarditis.

The authors concluded:

Patients with post–COVID-19 mRNA vaccination myocarditis, contrary to those with post–COVID-19 myocarditis, show a lower frequency of cardiovascular complications than those with conventional myocarditis at 18 months. However, affected patients, mainly healthy young men, may require medical management up to several months after hospital discharge.

Summary

As has been shown previously, there is a small (1 out of 100,000 vaccinations) risk of myocarditis after receiving the COVID vaccine. However, and this is often lost in the discussions, this risk is much lower than the risk of myocarditis from a COVID infection. Moreover, there is a much greater risk of hospitalization from myocarditis in individuals who have had a COVID infection or myocarditis from other causes compared to those who have had the COVID vaccine.

Yes, myocarditis has to be managed, especially in young men, if it appears after a COVID vaccination. But the long-term prognosis is excellent and most people who get post-vaccine myocarditis have excellent outcomes. The same cannot be said for those individuals who get myocarditis from the infection itself.

Anti-vaccine activists love to point to myocarditis as a reason not to get the vaccine. But they seem to ignore the cost-benefit calculation, which shows that catching COVID leads to a much higher risk for myocarditis. And it’s a worse version of the condition.

Myocarditis is not a reason to avoid the vaccine.

Citations

• Semenzato L, Le Vu S, Botton J, Bertrand M, Jabagi MJ, Drouin J, Cuenot F, Zores F, Dray-Spira R, Weill A, Zureik M. Long-Term Prognosis of Patients With Myocarditis Attributed to COVID-19 mRNA Vaccination, SARS-CoV-2 Infection, or Conventional Etiologies. JAMA. 2024 Aug 26:e2416380. doi: 10.1001/jama.2024.16380. Epub ahead of print. PMID: 39186694; PMCID: PMC11348078.