Myocarditis in children and young adults

The Centers for Disease Control and Prevention (CDC) recommends COVID-19 vaccination for everyone age 5 and older to reduce the risk of getting and spreading COVID-19. The vaccines are safe and highly effective at preventing severe illness, hospitalization and death from COVID.

Since April 2021, however, increased cases of myocarditis — an inflammation of the heart muscle — have been reported in the U.S. after people received either the Pfizer or Moderna COVID-19 vaccine, particularly in children and young adults. This leaves many parents wondering how worried they should be about this rare side effect.

What is myocarditis?
Myocarditis is inflammation of the heart muscle responsible for pumping blood in and out of the heart. The inflammation can reduce the heart's ability to pump and cause rapid or abnormal heart rhythms, also known as arrhythmias. Symptoms can include shortness of breath, chest pain, fatigue and a rapid or irregular heartbeat.

Most of the individuals who developed the condition after receiving a COVID-19 vaccine are male adolescents and young adults. The condition often occurs after the second dose and typically appears within a week of vaccination.

“Myocarditis appears to be an extremely rare side effect of the COVID-19 vaccine,” says Dr. Justin Parizo, a cardiologist affiliated with Sharp Memorial Hospital. “When this rare event occurs, the vast majority of people experience mild symptoms, and the disease resolves without treatment.”

What are the risks of myocarditis?
It’s understandable to worry about a side effect that could affect the heart. But before choosing not to vaccinate, it’s important to weigh the risks of myocarditis with the risks of COVID-19, Dr. Parizo says.

Parents should consider the following:

1. While it’s true that children and young adults have been less affected by COVID-19, there are many within these age groups who have gotten very sick and even died from COVID-19. In 2020, COVID-19 was a top 10 cause of death for children ages 5 to 11, and thousands of children have been hospitalized from the disease. Additionally, even children with no symptoms from COVID-19 can — and have — developed lasting symptoms or “long-haul COVID” weeks to months later. 

2. Long before the pandemic, thousands of cases of myocarditis were diagnosed in the U.S. and around the world each year, often triggered by typically benign viral infections. SARS-CoV-2, the virus that causes COVID-19, can trigger it as well. Other causes include bacterial infections, autoimmune diseases, and adverse reactions to medications and toxins. 

3. As of Dec. 15, 2021, more than 486 million doses of COVID-19 vaccines have been given in the U.S. And, as of Dec. 17, 2021, 2,168 cases of myocarditis among people age 30 and younger were reported to the Vaccine Adverse Event Reporting System (VAERS). However, identifying the cause of myocarditis can be very difficult and, while temporally associated with receiving a COVID-19 vaccine, further investigation is required to better understand the cause. 

4. If someone gets COVID-19, they are approximately 16 times more likely to develop myocarditis than individuals who don’t get the illness, according to the CDC, while the best data available suggests that people who receive the vaccine are approximately two to three times more likely to develop myocarditis than individuals who don’t receive the vaccine. And the risks to the heart from COVID-19 infection can be more severe.

Dr. Parizo joins other experts in recommending that getting vaccinated is the right health decision for both children and young adults. Individuals who are vaccinated can more safely go to school, play sports and be with their friends and families, he says, all of which are important for health and well-being.

“It’s understandable that some parents fear having their child vaccinated,” says Dr. Parizo. “The potential negative effects of a bad case of COVID-19 are far riskier than the minimal risk of developing myocarditis after vaccination as a result of getting the disease.”