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, 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's Monday, June the 14th. Recently there have been concerns that the messenger RNA, or mRNA, vaccines that are made by Pfizer and Moderna might cause myocarditis, which is inflammation of the heart muscle.

Now, the original studies that were done by the Centers for Disease Control and Prevention, otherwise known as the CDC, looked at all people who were either given the vaccine or not given the vaccine, and they found that there was really no difference in the incidence of this myocarditis in a vaccinated versus unvaccinated group. However, when they sub-stratified it, when they just looked at those people who were 16 to 39 years of age, and just looked at the second doses, they found that the incidence of myocarditis was greater in the vaccinated than unvaccinated group. So, I think that this is probably a real phenomenon, but it is rare, occurring in about 1 in 50,000 recipients. Now, the symptoms are transient, short-lived and self-resolving. They usually include chest pain, mild chest discomfort, and occasionally shortness of breath. Again, it usually occurs in boys and men.

And so, what to do? Should we vaccinate or not vaccinate given this rare, but real, apparently real side effect? So, here's one way to think of it. Imagine a stadium filled with 100,000 people, all of whom were boys or men between 16 and 39 years of age. In that group, if you vaccinate all of them, two will develop symptoms of myocarditis, which are generally short-lived and self-resolving. If you don't vaccinate any of them, if you leave all unvaccinated, about 1,300 will develop COVID. Now remember, myocarditis is an uncommon but real symptom associated with the natural infection with that virus, SARS-CoV-2. And it also is a common occurrence with this post-infectious phenomenon called multisystem inflammatory syndrome, which occurs both in children and adults, then you often see actually myocarditis. So again, it looks like vaccination is the safer, less risky choice.

Now, some people would argue given this rare side effect and given that children don't get severely infected, why not just not vaccinate children? Well, first of all, children do get infected. There have been about 4 million cases of disease reported in children, and those are just people who've been tested and found to be infected. About 550,000 of those cases occurred in children between 0 and 4 years of age. But there were about 40,000 hospitalizations, 300 deaths, and at least 4,000 reported cases of this multisystem inflammatory syndrome of children, which again is often associated with cardiac involvement, i.e., heart-muscle involvement. So, I think children are vulnerable. Children can get infected. And remember that infection can cause a heart disease in children, and then this multisystem inflammatory disease often causes heart disease in children.

Or people argue, well, you know, it looks like the disease is going away. I mean, now we're just having really only thousands of cases a day and only sort of low hundreds of cases [deaths] a day, the numbers are clearly going down. But I think you have to remember a few things, and the numbers clearly have been good lately. I mean, the number of cases, the number of hospitalizations, the number of deaths are clearly going down. But it's summer, and SARS-CoV-2 is a winter virus. And if you don't believe that, just look at the deaths when this virus first came into the country. When the virus first came into the United States and started killing people in March of last year, you saw 1,000 deaths a day, 1,500 deaths a day, 2,500 deaths a day. And then as we approached April, May and June, the numbers started to come down. This is last year. Last summer when we had a fully susceptible population, last summer when we had no vaccine, the numbers came down over the summer. And then when we hit November, December, those numbers of hospitalizations, deaths and cases dramatically increased. And now they've started to come down again. And I think they've come down because it's summer and because we have vaccines that are out there now. Almost 70% of the population is vaccinated, and we have a lot of people who've been naturally infected who are also protected, but it is a winter virus.

I think the second thing to know is the variants. The first variant that came into this country, which was called the D614G variant, that's the one that swept through Europe. That's the one that swept through the United States. That's the one that really killed 500,000 people, has been replaced by a second variant, the so-called B.1.1.7 variant, or Alpha variant, or UK variant; that's taken over because it's more contagious. And now you have another variant that's coming to this country, the so-called B.1.617 variant, the Delta variant, that came out of India initially and is killing now just thousands of people in India, is now starting to double in this country. So the variants, because they're more contagious means you need to have a highly vaccinated population if you're going to stop the spread.

Also remember there are 195 countries in this world, many of which have not given a single dose of vaccine. As long as this virus exists in the world, we're going to need to have a highly vaccinated population, and that includes children.

So, I think the bottom line here is that vaccination is important. I think vaccination is going to be important in this country to keep us highly protected for not just years, but likely longer than that.

Thank you.

Related Centers and Programs: Vaccine Education Center

Last Reviewed on Jun 14, 2021