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A new study looks at myocarditis following COVID-19 vaccines. Rouelle Umali/Xinhua via Getty Images
  • There have been reports of suspected myocarditis linked to COVID-19 vaccinations in adolescents and young adults.
  • A North American study shows that most of these individuals experience rapid recovery from symptoms.
  • More research is necessary to determine the long-term effects of COVID-19 vaccine-related myocarditis.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Rare cases of myocarditis, an inflammation of the heart muscle, have been associated with COVID-19 vaccinations in adults in Israel and the United States military.

While most of these cases occurred in males younger than 30 years, researchers have also reported suspected incidences of the condition in adolescents.

On June 23, 2021, the Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices reported a likely link between mRNA COVID-19 vaccination and myocarditis, particularly in those younger than 39 years.

Because of the important health implications in the decision to vaccinate youth, it is vital to understand the effects of suspected myocarditis following COVID-19 vaccinations.

A recent study in the American Heart Association’s (AHA) flagship journal, Circulation, suggests that young people who experienced the myocarditis side effects from COVID-19 vaccinations recover quickly.

Researchers collected data from 26 centers across the U.S. and Canada. Using CDC guidelines to classify cases of myocarditis as probable or confirmed, 139 patients younger than 21 showed symptoms of myocarditis within 1 month of receiving a COVID-19 vaccination prior to July 4, 2021.

Of the 139 teens and young adults meeting the study criteria, most were white, non-Hispanic, and male, with a median age of 15.8 years.

According to symptoms, laboratory data, and imaging results, around one-third of the cases of suspected myocarditis were classified as confirmed and two-thirds as probable.

Almost 98% of all cases followed an mRNA vaccine, and 91% occurred after the second vaccine dose. Chest pain, fever, and shortness of breath were the most common symptoms the patients reported.

More than 75% of those who received a cardiac MRI showed evidence of inflammation or injury to the heart muscle. Most of these individuals were in the hospital for 2–3 days, with their illness considered mild. About 20% of the hospitalized patients were admitted to ICU, and there were no deaths.

However, the research team noted several limitations of the study. For example, there was no comparison of the incidence or risk between those who experience myocarditis because of the vaccination with those who experience cardiac symptoms following COVID-19 infection.

In addition, the authors could not rule out the possibility of a viral infection causing the myocarditis.

The authors note the need for future studies to evaluate the long-term outcomes for those who have had myocarditis after COVID-19 vaccinations.

Underlying genetic differences or immune responses make males especially susceptible to developing this cardiac condition. Scientists do not know these apparent risk factors.

Dr. Sanjay Prasad, a cardiologist at Mayo Clinic, London, spoke to Medical News Today regarding the need for specific follow-ups to this study:

“Important questions to address are why was this subset more susceptible, and for those developing myocarditis after one dose, how and when should they receive the second dose?”

In an interview with MNT, Dr. Ryan Serrano, assistant professor of Clinical Pediatrics at Indiana University School of Medicine and cardiologist at Riley Children’s Health, both in in Indianapolis, explained how the results chimed with his own observation:

“The patient characteristics and outcomes described here are consistent with our own experience with post-vaccine-related myocarditis, in that most cases are mild without severe involvement, such as cardiac dysfunction or arrhythmia, and patients recover quickly, especially compared with patients who get myocarditis from a viral infection like COVID-19.”

He also agrees with the need for more research relating to the future safety of people with myocarditis, especially those who are athletes:

“Athletes who experience viral myocarditis must be restricted from sports for 3–6 months,” says Dr. Serrano. However, as supported by this study, post-vaccine myocarditis seems to be milder with a faster recovery time. “Do these athletes need to rest for 3–6 months, or can they safely return to the field sooner?” he adds.

The researchers state that myocarditis, even if mild in the majority, is a cause of great concern. However, the risk must be balanced against critical illness associated with COVID-19.

“Overall, I still think the personal and public health benefits significantly outweigh the risk, and I still recommend all parents to get their children vaccinated when they are age-appropriate.”

– Dr. Serrano

The researchers conclude that COVID-19 vaccine myocarditis occurring in those younger than 21 years is resolved rapidly with only mild symptoms.

However, they recommend healthcare professionals be alert to boys and young male adults who present with chest pain after receiving a COVID-19 vaccination, especially in the first week after the second vaccination.

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