Myocarditis and COVID-19 Vaccines: The Latest News for Parents
Three expert physicians share the facts on this rare reaction—and why vaccinating your child is still the safest choice.
By Katie Sweeney
Many parents have been concerned about reports of myocarditis—heart inflammation—in some young people who have received a COVID-19 vaccine.
This worry is understandable. But there’s also reassuring news: Heart inflammation after the vaccine is a very rare event. In addition, most cases have been mild, with patients recovering after a few days of treatment and rest.
Below, Children’s Hospital Los Angeles physicians—Jennifer Su, MD, a pediatric cardiologist, Sindhu Mohandas, MD, a pediatric infectious diseases specialist, and Michael Neely, MD, MSc, FCP, Chief of Infectious Diseases—explain what’s happened, the symptoms to look for and why vaccinating your child is still by far the safest choice.
What exactly has happened?
Health officials have observed an increased risk for heart inflammation in adolescents and young adults who have received either the Moderna or Pfizer-BioNTech vaccines. Most of these cases have been in teen boys and young men, ages 12 to 29. The Pfizer vaccine is authorized for use in patients as young as 5 years old; Moderna is authorized in patients 18 years and older.
Both myocarditis and pericarditis have been reported. Myocarditis is inflammation of the heart itself, and pericarditis is inflammation of the heart’s outer lining.
The risk of this reaction is when the vaccine is given to people ages 12 to 18. Children 5 to 11 years old became eligible to receive a lower dose vaccine in early November 2021. In studies of more than 8 million vaccine doses administered to children ages 5 to 11 who received the Pfizer vaccine, there appears to be an even smaller risk of developing myocarditis—only seen in boys after the second dose (roughly 4 cases of myocarditis in a million). No increased myocarditis risk was seen in girls ages 5 to 11.
How serious is it?
Heart inflammation is always taken seriously. But fortunately, most post-vaccine cases in young people have been short-lived, with patients getting better very quickly.
“It’s still early, but we don’t expect them to have any long-term consequences,” Dr. Su says. “In the majority of patients, their heart function has been completely normal. We monitor them very closely, but typically they are treated with nothing more than ibuprofen.”
In contrast, traditional cases of myocarditis in adolescents—typically caused by a viral infection—are often more severe. “This specific post-vaccine reaction generally falls in the milder spectrum of myocarditis,” she notes. “Certainly, the risk of long-term health problems, including myocarditis, is much higher after a COVID infection than after the COVID vaccine.”
What are the symptoms?
Symptoms usually appear within a few days of receiving the Moderna or Pfizer vaccine, particularly after the second dose. The most common symptoms are:
- Chest pain
- Shortness of breath
- Heart palpitations (fast heartbeat)
What if my child has this rare reaction?
“You should see your pediatrician, ideally within a day of the symptoms starting,” Dr. Neely says. “Be aware that other conditions besides myocarditis could cause these symptoms, too. It’s important to find out what’s happening.”
There are two very simple tests your doctor can do to quickly check if your child has myocarditis:
- A blood test to test for a protein that’s released when heart inflammation is present
- An electrocardiogram (EKG), which measures the heart’s rhythm and electrical activity
How is myocarditis treated?
Children with myocarditis are often hospitalized. Most patients with post-vaccine myocarditis have responded well to rest and ibuprofen and have gone home after a few days.
“We hospitalize patients to monitor them,” Dr. Su explains. “It’s usually out of an abundance of caution to make sure they’re safe and the inflammation completely resolves.”
As of March 2022, Children’s Hospital Los Angeles has treated only nine confirmed cases of myocarditis in adolescent boys who had recently received a COVID-19 shot. It has not been determined if all those cases were caused by the vaccine.
Should my child still get a COVID-19 vaccine?
Yes, absolutely. This reaction is very rare and usually short-lived. The reality is there is no completely risk-free choice. Young people actually face a greater risk of myocarditis from COVID-19 itself. For example, a recent study of Big Ten college athletes who had previously had COVID-19 found that 2.3% of them showed signs of heart inflammation on cardiac MRIs.
“As a cardiologist, I am much less concerned about a very rare and usually self-resolving vaccine reaction than I am about COVID-19 and how it can impact our kids,” says Dr. Su. “The benefits of the vaccine far outweigh the risks.”
Dr. Su notes that in the past year, COVID has been among the top 10 causes of death among children ages 5-11, and was linked to 40% of all myocarditis cases in kids. In contrast, Dr. Mohandas says that only 4 cases of myocarditis were reported per million doses administered in this age group. Clinical trials in children 5-11 years have found the vaccine to be more than 90% effective in preventing severe COVID-19 infection. Dr. Neely adds that over 11 billion doses of various COVID-19 vaccines have been given around the world so far. “With any therapy or medicine, there will always be rare events,” he says. “But these vaccines are among the safest and most effective ever developed. We have a lot of data now to show that.”
But aren’t kids and teens less likely to get severe illness from COVID-19?
Yes, but it’s not that simple. Adolescents and young adults who get COVID-19 can go on to develop sequelae like MIS-C or long COVID even if the initial illness was mild or asymptomatic. And contrary to popular belief, children and adolescents unfortunately can and do get hospitalized for COVID-19 (although not as often as adults)—and some have died.
A simple shot can prevent those outcomes. Vaccines were somewhat less effective at preventing infections with the Omicron variant, but were just as effective at preventing hospitalizations and death, the vast majority of which occurred in unvaccinated individuals. Vaccinating young people will help to keep community infection rates low, and slow the creation of new variants.
“With most places dropping mask mandates, it is more important than ever before that children’s vaccinations are up to date,” says Dr. Mohandas.
“These vaccines are amazingly protective against severe disease and hospitalization,” Dr. Neely adds.
What if I still have questions or concerns?
Dr. Neely urges parents who feel unsure about the vaccine to talk with their pediatrician about their concerns.
A parent himself, he booked his 15-year-old son’s appointment to get the COVID-19 vaccine just two hours after his son became eligible.
“An hour later we were in the pharmacy with a needle in his arm,” Dr. Neely says. “I would do the same thing again today in a heartbeat. Because I know now that he’s protected, and he’s doing his part to protect his friends and neighbors, too.”