Myocarditis and the COVID-19 vaccine: What to know about rare heart inflammation

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Health experts say the Pfizer and Moderna COVID-19 vaccines are safe following rare incidents of heart inflammation, mostly among young men and teenage boys.

There have been more than 300 verified cases of myocarditis among 12- to 29-year-olds in the U.S. believed to be related to the mRNA vaccines. More than 140 million people in the country have been fully vaccinated with the Pfizer and Moderna vaccines.

Most of the myocarditis patients experienced symptoms a few days after the second shot. Of 309 people who were hospitalized, 218 of them have recovered from their symptoms. As of last week, nine patients were still hospitalized and two of them were in the ICU, according to the Centers for Disease Control and Prevention.

“I think it’s important to be aware of risk, but also to weigh risk in an informed fashion,” said Howard Julien, a Penn Medicine cardiologist and assistant professor of cardiovascular medicine at the University of Pennsylvania.

Julien said these cases must be considered in context.

“The potential harms, not just the dreaded harm of death, but also the long-term consequences of COVID-19 in terms of long-standing, lingering pulmonary and neurologic issues that many long-haulers have experienced, should be weighed against a very small, non-zero, but very small, minuscule risk of myocarditis,” he said.

“The risk of death from a car accident or opioid overdose are far greater than the risk of myocarditis, and I think that it’s important to have a balanced conversation about relative risk of things that we encounter in everyday life and that are ever-present dangers along with the risks of an exceedingly rare complication of vaccination that results in widespread recovery.”

The Food and Drug Administration on Saturday revised its Pfizer and Moderna guidance for patients and providers to include a warning about myocarditis and pericarditis.

The update follows a Wednesday meeting of the CDC’s Advisory Committee on Immunization Practices, during which the adverse event of heart inflammation was discussed.

The fact sheets for health care providers now warn about the incidents and advise medical attention for patients experiencing chest pain, shortness of breath, or fast-beating, fluttering, or pounding heart after vaccination.

Myocarditis is inflammation of the heart muscle, and is typically more common in teen boys and younger men.

Unlike myocarditis caused by the vaccines, traditional myocarditis is most often caused by viruses, such as Hepatitis C, HIV, and Influenza A. Heart inflammation can also be caused by parasitic, fungal, and bacterial agents, as well as illicit drugs, prescription medications, and immunological syndromes.

Symptoms can include chest pain, pressure or discomfort, shortness of breath, and palpitations. Traditional myocarditis can be treated with supportive care, such as oxygen or fluids, anti-inflammatory medicines, or in severe cases, with mechanical support or a heart transplant. Unlike the incidents related to the vaccines, traditional myocarditis is usually more severe. But for both cases, patients must reduce exercise for three to six months.

“There are viruses that cause myocarditis and it can be quite severe, meaning it can cause chronic disease, which can lead to a heart transplant. It can cause severe acute disease that can lead to death and ICU admission. So that’s not this,” said Paul Offit, director of the Vaccine Education Center and an attending physician in the Division of Infectious Diseases at Children’s Hospital of Philadelphia.

“The myocarditis following these MrNA vaccines … is short-lived, temporary, self-resolving, a mild inflammation of the heart that goes away. It’s not based, obviously, on viruses reproducing themselves to the heart muscle because you’re not getting the virus … So this is a very different thing.”

People who develop myocarditis after the first dose of the COVID-19 vaccine should talk to their doctors before getting the second shot.

Experts say the benefits far outweigh the risks. The overall efficacy of the MrNA vaccine is 95%. In December, there were about 250,000 COVID-19 cases and 3,000 deaths per day. By comparison, after millions of Americans were vaccinated by June, there were about 13,000 COVID cases and 300 deaths per day.

Though fewer children contract COVID-19, and fewer kids and young adults experience serious illness, there’s still some risk of contracting the virus. Since the beginning of the pandemic, at least 7.7 million COVID-19 cases have been reported among people ages 12 to 29. In May, that age group represented 33% of COVID-19 cases. Since the beginning of the pandemic, 2,767 coronavirus deaths have been reported among this age group.

Children are also getting diagnosed with MIS-C, a severe hyperinflammatory syndrome occurring two to six weeks after acute COVID-19. Of those patients, 60% to 70% are admitted to intensive care, and 1% to 2% of cases are fatal.

Offit pointed to a recent study of Big Ten athletes who had COVID-19 which found that roughly one in 45 had myocarditis, “which is much more common than the one in 50,000 that occurs with vaccines,” he said.

Of children who get MIS-C, Offit said three out of every four get myocarditis.

“So the choice not to get a vaccine is not a choice to avoid the risk of myocarditis — quite the opposite,” he said. “It’s a choice to take a greater risk of getting myocarditis.”

Julien added that if kids contract COVID-19, it could also harm people around them who are unvaccinated.

“And so really, the benefit of vaccination is not just for the children themselves, but also for the society as a whole,” Julien said.

“And the longer we go without vaccinating as many people who are eligible as possible, the more likely we will see the rise and the dawn of variants that may become more infectious within younger populations, and maybe they result in higher degrees of chronic illness and death,” Julien added. “And I would say that this is our chance to curtail the pandemic and curtail the development of variants that would be increasingly dangerous to children and adults.”