What Should I Know About COVID-19 Vaccine and Myocarditis in Teens?

Dr. Paul Offit discusses myocarditis, an inflammation of the heart muscle, related to receipt of the COVID-19 vaccine in teens and student athletes, and considerations related to the relative risks and benefits of vaccination compared with vulnerability to COVID-19.


What should I know about COVID-19 vaccine and myocarditis in teens?

Paul Offit, MD: Hi, my name is Paul Offit. I'm talking to you today from the Vaccine Education Center at the Children's Hospital of Philadelphia. It is Tuesday, November 16th, 2021. When the mRNA vaccines were first tested and presented to the Food and Drug Administration in December of last year, those studies were, in the case of Pfizer, studies of about 40,000 adults, half of whom got vaccine, half of whom got placebo. And in the case of Moderna, about 30,000 adults, half of whom got vaccine, half of whom got placebo. So, in the case of Pfizer, there were roughly 20,000 adults who got vaccine. In the case of Moderna, about 15,000 adults got vaccine. What wasn't seen in any of those trials was a serious side effect. However, when these vaccines were then given not to millions, but tens of millions and hundreds of millions of people, a very, very rare side effect emerged, called myocarditis, which literally means inflammation of the heart muscle. It was rare. Depending on what age you were looking at, it was between 1 in 20,000 to 1 in 50,000. It was that rare. But for the younger male who got the second dose, say as an 18-year-old, 19-year-old, it could be as high as 1 in 10,000. So, for that reason, people are concerned, reasonably, about myocarditis.

Now, the good news about myocarditis, at least following a vaccine, is that it tends to be very short-lived, transient and self-resolving. It's not like what we think of as typical viral myocarditis. So, typical viral myocarditis caused by viruses that have names like coxsackievirus can be quite severe, invariably resulting in a hospital admission, often resulting in intensive care unit admission, and also about 5 to 10% of the time resulting in the necessity for a heart transplant. That's not this. In some ways I wish we didn't call it myocarditis because when you hear that term, it makes physicians certainly think of this other sort of classic myocarditis that's caused by viruses. That's not this. This is a short-lived phenomenon.

Now, you should also know that the virus itself, SARS-CoV-2, COVID, is associated with myocarditis. There was a study done in athletes in the Big Ten conference, so these are sort of older adolescents/young adults who had COVID. And what they did was they did a very sensitive heart imaging study on every one of those people, independent of whether or not they had heart symptoms. And they found that roughly 2.5% of that group, so roughly 1 in 45, who were infected with the virus had evidence of myocarditis. Also remember MIS-C, this multisystem inflammatory disease is also a cause of myocarditis about half the time or as much as 75% of the time. And in those two cases, meaning the myocarditis caused by the virus or myocarditis caused by this MIS-C, which is a post-infectious inflammatory phenomenon associated with COVID, is more severe than that caused by the vaccine. So, there are no risk-free choices. A choice to get a vaccine is a much less serious risk. And we know now that for the 12- to 15-year-old, the risk of myocarditis appears to be less than it was say for the 16- to 25-year-old. And remember the 5- to 11-year-old is getting a dose that’s only one-third of that that was given to the 12- to 15-year-old. So, the suspicion is then, or the prediction is that the incidence of myocarditis would be even rarer in that group.

But I think parents should take heart in the fact that this myocarditis phenomenon appears to be short-lived, transient and self-resolving and nothing like the myocarditis, classic myocarditis, we saw with typical viral infections.

Thank you.

Related Centers and Programs: Vaccine Education Center

Last Reviewed on Dec 15, 2021