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The CDC is investigating if heart inflammation is related to vaccinations in teenagers. Boston Globe/Getty Images
  • The agency is reviewing “relatively few” reports of adolescents and young adults who developed myocarditis after vaccination. No link has been found to the vaccines.
  • These cases of myocarditis, or inflammation of the heart muscle, may be unrelated to vaccination. This condition can be caused by viral, bacterial, and other infections. 
  • Myocarditis can also occur in people who have had COVID-19.

The Centers for Disease Control and Prevention (CDC) is investigating a small number of reports that adolescents and young adults who received an mRNA COVID-19 vaccine have experienced heart problems, according to the agency’s vaccine safety group.

These cases of myocarditis, or inflammation of the heart muscle, may be unrelated to vaccination. This condition can be caused by viral, bacterial, and other infections. 

Myocarditis can also occur in people who have had COVID-19.

The vaccine safety group’s statement said there were “relatively few” cases. The rate of reported cases among vaccinated young people is not higher than the rate in the general population.

The chance of developing myocarditis in the wider population is rare — 10 to 20 cases occur per 100,000 people.

Still, the group felt that healthcare providers should be aware of this “potential adverse event” after vaccination.

Cases occurred primarily in adolescents and young people within 4 days after receiving their second dose of the Moderna-NIAID or Pfizer-BioNTech vaccine. Cases were more common in males than females.

Both vaccines have been approved in the United States for people 16 years and older. The Pfizer-BioNTech vaccine was recently approved for use in 12- to 15-year-olds.

“Most cases appear to be mild, and follow-up of cases is ongoing,” the vaccine safety group said. The group called for further study.

The European Medicines Agency (EMA) recently requested data from Moderna on reports of myocarditis and pericarditis after vaccination. 

Dr. Ihab B. Alomari, a cardiologist with UCI Health in California, said the cases of myocarditis reported to the CDC are not necessarily caused by the vaccine. 

“We still need to wait for more people to get vaccinated in order to see if the rate of people who get myocarditis after vaccination is higher than normal,” he said.

Given the health risks of COVID-19, including long-haul COVID, experts recommend that teens and young adults get vaccinated.

“So far, all the myocarditis cases that were reported were actually mild,” Alomari said. “But COVID itself is more dangerous than getting the vaccine. So the benefits of vaccination at this point definitely outweigh the risk.”