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What do we know about heart muscle inflammation after COVID-19 vaccination?

This article was published on
July 2, 2021

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Heart muscle inflammation or "myocarditis" has appeared in a small group of people, mostly men under 30, who recently received a COVID-19 mRNA vaccine.

Heart muscle inflammation or "myocarditis" has appeared in a small group of people, mostly men under 30, who recently received a COVID-19 mRNA vaccine.

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What our experts say

Heart muscle inflammation or "myocarditis" has appeared in a small group of people, mostly men under 30, who recently received a COVID-19 mRNA vaccine.

The United States Centers for Disease Control and Prevention is monitoring the cases in young adults and said there is a "likely association" between the vaccines and reported cases of heart inflammation, but there is not a deep enough understanding of this issue to understand why vaccines may contribute to the condition. The group calls these events "important but uncommon" as they are highly rare.

Heart muscle inflammation, otherwise known myocarditis, is a condition caused most commonly by viral infections. It can also be caused by bacterial or fungal infections, autoimmune diseases, severe reactions to medicines, and exposure to certain environmental toxins. Common symptoms of myocarditis include chest pain, shortness of breath and heart palpitations. It most frequently occurs in young men, and those with pre-existing medical conditions. Myocarditis is a rare condition and is most commonly treated with medicines over a week to ten days. Very rarely, myocarditis can lead to hospitalization. 

In a recent press conference, the US Centers for Disease Control said that according to early vaccine safety data, myocarditis does appear to show up more frequently than normal in some groups fully vaccinated against COVID-19. The CDC highlighted that these numbers were in line with the clinical trial data based on which these vaccines were authorized for emergency use by the Food and Drug Administration.

It is important to note that myocarditis has also been linked to people who have been infected with COVID-19, in addition to other issues like blood clots, strokes, heart attacks, and more.

At this stage, the CDC continues to advise vaccination for young adults, with precautions to be taken for those who have pre-existing medical conditions, and those that report any symptoms of myocarditis after their first dose. Based on the data available at this time, the clinical prognosis for the small number of individuals who suffered from myocarditis post-vaccination were seen to be encouraging. 

The risk of hospitalization from COVID-19 is also an order of magnitude higher, even in younger age groups, than the risk of suffering from myocarditis post-vaccination. Based on the current evidence, the CDC recommends continuing with vaccinations for younger age groups including children. 

Context and background

Some recently published studies have highlighted the slightly increased rate of heart muscle inflammation in children and young adults who have received the Pfizer-BioNTech and Moderna vaccines. These studies, published since the Food and Drug Administration approved the emergency use of these vaccines in adolescents in early May.

Resources

  1. Heart Inflammation (NHLBI, NIH)
  2. Federal health officials find vaccine benefits outweigh small cardiac risk for teens, young adults (The Washington Post)
  3. Trends in Acute Myocarditis Related Pediatric Hospitalizations in the United States, 2007–2016 (ScienceDirect)
  4. The effects of gender and age on occurrence of clinically suspected myocarditis in adulthood | Heart (bmj.com)
  5. Myocarditis after BNT162b2 and mRNA-1273 Vaccination | Circulation (ahajournals.org)
  6. Surveillance of Myocarditis (Inflammation of the Heart Muscle) Cases Between December 2020 and May 2021 (Including) | Ministry of Health (www.gov.il)
  7. Myocarditis Temporally Associated with COVID-19 Vaccination (ahajournals.org)
  8. Symptomatic Acute Myocarditis in Seven Adolescents Following Pfizer-BioNTech COVID-19 Vaccination (American Academy of Pediatrics (aappublications.org))
  9. COVID Vaccines In Teens And Heart Inflammation: What You Need To Know : Shots - (Health News : NPR)
  10. The Link Between Myocarditis and COVID-19 mRNA Vaccines (Yale Medicine)

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