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Myocarditis Reported as Rare Adverse Event from COVID-19 Vaccine

Jan. 7, 2022

Why the worry? What You Should Know about Myocarditis and COVID-19 Vaccination.


Why the worry? Myocarditis and COVID-19 Vaccination

Hesitation around the COVID-19 vaccine developed when cases of myocarditis, a common inflammation of the heart muscle, or myocardium, were reported in predominantly males under the age of 40. Myocarditis is reported as a rare adverse reaction to the COVID-19 vaccine.

Myocarditis is often naturally accompanied by pericarditis, which is the inflammation of the pericardium, a protective covering on the surface of the heart.

The exact cause of myocarditis associated with mRNA vaccines is not currently known. Reported cases have been seen within several days of a second dose of either Moderna or Pfizer-mRNA vaccines. Myocarditis or myopericarditis have not been reported after AstraZeneca or Johnson and Johnson vector vaccines.

However, most cases have occurred in men younger than 40 years of age within one week of the second injection, with the most common being between 19 and 26 years old. Potential causes include allergic reactions to one or more component parts of the vaccine, such as lipid particles or polyethylene glycol, molecular imitation between the spike protein of the coronavirus and self-antigens, trigger of preexisting dysregulated immune pathways in certain individuals, immune response to mRNA and activation of immunologic pathways. The greater proclivity in males may be related to sex hormones, differing immune responses and possibly under-reporting in females.

“There have been cases of myocarditis and myopericarditis following smallpox, influenza, human papilloma, typhoid, hepatitis B, meningococcal, anthrax and Japanese encephalitis vaccine administration,” said Richard Becker, professor of medicine, director of the Division of Cardiovascular Health and Diseases, director of the University of Cincinnati Heart, Lung & Vascular Institute. He said “each are considered rare.”

The most common symptom of myocarditis is chest pain.

“Other symptoms include shortness of breath, palpitations, dizziness or lightheadedness,” said Dr. Becker. “Symptoms occurred within one week of vaccination, predominantly after the second dose.” Cases of myocarditis have not been reported to date following a booster dose.

Most myocarditis cases can be treated with rest, close observation and anti-inflammatory medications.

The CDC continues to recommend vaccination for everyone 12 years of age and older, including those with chronic heart conditions who are known to be at risk for life-threating cases of COVID-19. Children ages 5 and above can receive the Pfizer vaccine at the approved doses. Vaccine- associated myocarditis is rare in children, and if occurring, the inflammation is minimal.

Receiving a vaccination is the best way to protect yourself from COVID-19. The Food and Drug Administration encourages individuals to consider the risks and benefits with the Pfizer-BioNTech or the Moderna COVID-19 vaccines. If the decision is made to not receive a vaccination, it is extremely important to continue social distancing and wearing a mask.

Dr. Becker provided the following information about the risk of developing myocarditis from COVID-19, influenza and other vaccines.

  • 12.6 cases of myocarditis per million doses of the mRNA vaccine were reported. The risk of death following COVID-19 vaccine administration is 0.0018 percent.    
  • Prevalence of myocarditis in patients with COVID-19 is 0.2 to 0.4 percent.  
  • In patients with severe COVID-19 requiring an ICU and mechanical ventilation, the incidence of myocarditis may be as high as 1-2 percent.
  • Influenza can also cause myocarditis and pericarditis. The incidence is 1to 2 per 1000 cases of 0.1 to 0.2 percent.

The Greater Risk: Myocarditis After Having the COVID-19 Virus

Current research has found that there is a much greater risk of developing symptoms of myocarditis from the COVID-19 virus as opposed to the mRNA vaccine.

In terms of numbers, during the first 12 months of the COVID_19 pandemic, males aged 12 to 17 were most likely to develop myocarditis within three months of catching COVID-19, at a rate of about 450 cases per million infections.

According to a study in July of 2021, published by the Journal of the American Medical Association , 60 percent of COVID-19 survivors, no matter the severity of the illness, had developed myocarditis.

In a comparison of numbers, the COVID-19 mRNA vaccines show less of a risk in developing myocarditis.  Subsequently, risking contracting the virus by opting out of the vaccine comes with many other symptoms and potential long-term effects from the virus itself. As Benjamin Franklin once said, “an ounce of prevention is worth a pound of cure.”