The Mayo Clinic defines myocarditis as an inflammation of the heart muscle that can reduce its ability to pump and cause rapid or abnormal heart rhythms, known as arrhythmias. While this condition can clear without permanent complications, severe instances can result in heart attacks, stroke or sudden cardiac arrest.

Any reasonable person who believes that COVID-19 vaccines cause myocarditis would be hesitant to receive one and owes themselves the opportunity to get informed on the potential risk,” said Vik Ramaswamy, Senior Risk Control Manager at Safety National. “But when considering risks, a reasonable person has to make sensible comparisons, such as ‘what is the risk of this arising from a COVID-19 vaccine versus the risk from a COVID-19 infection?’”

In part two of our COVID-19 employer vaccination series, we explore the most current primary research available from scientific publications, with no conflicts of interest or direct association with the Center for Disease Control (CDC).

What is the Chance of Myocarditis Occurring After a COVID-19 Vaccination?

Researchers published a comprehensive analysis of the efficacy and safety of COVID-19 vaccines in the journal Molecular Therapy. They characterized vaccine-related adverse drug reactions, or ADRs, by frequency per million doses. Per their analyses, they identified that only two or three cases of myocarditis/pericarditis occurred per million doses given. To put that in perspective, 0.0003% of vaccine doses administered may have resulted in myocarditis.

A study did assess cases of myocarditis occurring in patients after receiving COVID-19 vaccines. The researchers concluded that among the few instances that myocarditis did occur, they presented in younger males after the second dose of an mRNA-based vaccine, such as Pfizer or Moderna. Notably, all 15 patients included by the study criteria had symptoms clear within six days of diagnosis with full preservation of the cardiac function and no other adverse effects in the short term.

These studies indicate that very few instances of COVID-19 vaccination result in myocarditis, and when they correspond with symptoms, they are minor, and the heart retains full function upon recovery.

What if Those Statistics are Compared to Occurrences in COVID-19 Patients?

Researchers from Ohio State University performed cardiac magnetic resonance imaging of 1,597 college athletes diagnosed with COVID-19. The results indicated that 2.3% of the athletes were diagnosed with clinical or subclinical (not severe enough to show symptoms) myocarditis.

A much larger study conducted in Europe reviewed medical records of 718,365 COVID-19 patients and concluded that 5% were diagnosed with new, onset myocarditis and 1.5% with new, onset pericarditis.

We can compare these numbers using a tool from epidemiology called the risk ratio. Dividing the 5% of symptomatic COVID-19 infections that result in myocarditis by the 0.0003% resulting from COVID-19 vaccines, those infected with COVID-19 are 16,667 times more likely to present with myocarditis from a COVID-19 infection than from getting a COVID-19 vaccine, based on the data from the studies presented.