Why heart condition seen in few young people after COVID vaccine is no cause for alarm

A federal COVID-19 vaccine safety group has brought attention to “relatively few reports” of myocarditis — inflammation in the heart muscle — following vaccination with the Pfizer or Moderna shots, mostly among teens and young adults.

Officials did not reveal how many cases have been reported so far, but most of them “appear to be mild” and occur more often in males, after the second dose and within four days of vaccination, according to a May 17 report by the Centers for Disease Control and Prevention group.

The CDC said the rates of myocarditis following vaccination are similar to those that occur in the general population, but members of the safety monitoring group “felt that information about reports of myocarditis should be communicated to providers.”

The agency said it continues to monitor reported cases, but it has not determined whether the vaccines caused the condition. Officials did not comment on whether the Johnson & Johnson coronavirus vaccine has caused similar reactions among young people.

Still, experts say the benefits of vaccination far outweigh the risks of developing the heart condition and of contracting COVID-19.

“We know that COVID infection itself can be very serious and that we’ve lost hundreds of children and thousands have been hospitalized. So even if there is a connection with the vaccine — and right now, we don’t know that there is — we do know that COVID infection itself is much more serious than that,” former acting director of the CDC Dr. Richard Besser said Monday on NBC News’ “TODAY.”

“So I would recommend that parents go ahead and get their kids vaccinated,” added Besser, who is the CEO of the Robert Wood Johnson Foundation.

Myocarditis is diagnosed in 10 to 20 per 100,000 people each year, according to the American Heart Association, with many cases resolving on their own or with treatment, leading to full recoveries. It’s typically the result of an infection caused by a virus.

The condition causes the middle layer of the heart wall muscle to become inflamed, weakening the heart. Severe cases can lead to abnormal heartbeat, heart failure and sudden death. Common symptoms include chest pain, irregular heartbeat and unexpected shortness of breath.

Early in the pandemic, scientists and doctors learned myocarditis was prevalent among hospitalized COVID-19 patients; it was thought that as many as 1 in 5 patients developed it.

The condition first garnered national attention among young, healthy athletes. One study found that out of 460 athletes who had COVID-19, just five of them (less than 1%) developed inflammatory heart disease — three with myocarditis and two with a similar heart condition called pericarditis.

Now that the condition has been reported after COVID-19 vaccination, Besser told NBC News that experts want to make sure it “isn’t just coincidence, and that none of [the cases] were caused by the vaccine itself.”

“This is one of the most challenging things whenever there is a new medication or a new vaccine: to tell if something is caused by it or is it something you’d normally expect to see,” Besser said. “There are a lot of different viruses that can cause myocarditis. As the warm weather comes, that’s when we tend to see those viruses. There’s also drugs and other inflammatory conditions that could do this. So you would expect to see a certain number and [the CDC is] seeing that number.”

The American Heart Association still urges all adults and children ages 12 and up to get vaccinated against COVID-19 as soon as they can.

“We remain confident that the benefits of vaccination far exceed the very small, rare risks. The risks of vaccination are also far smaller than the risks of COVID-19 infection itself, including its potentially fatal consequences and the potential long-term health effects that are still revealing themselves, including myocarditis,” the group said.

“The recommendation for vaccination specifically includes people with cardiovascular risk factors such as high blood pressure, obesity and type 2 diabetes, those with heart disease, and heart attack and stroke survivors, because they are at much greater risk of an adverse outcome from the COVID-19 virus than they are from the vaccine.”

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