The real risk of heart inflammation to kids is from COVID-19—not the vaccine

Elizabeth Brown, a mother of two who lives outside Denver, Colorado, had a tough decision to make when childhood COVID-19 vaccines became available. Her five-year-old was born with a congenital heart defect that required a risky surgery when he was two years old to avoid a lifelong risk of heart inflammation from infection. But Brown also knew that after getting some COVID-19 vaccines, adolescent boys are at risk of developing myocarditis, a different kind of inflammation of the heart.

”To read about children with no cardiac history having myocarditis as a pediatric vaccine complication was scary,” Brown says. “There were a lot of inflammatory headlines from the media that preyed on a parent’s fear in terms of the vaccination and very little information readily available regarding the damage COVID can do.”

Brown spoke with her son’s cardiologist and mulled it over for weeks. As more information came out, she says, “I became more confident in vaccination.” Her son received his first vaccine dose two weeks ago.

Many pediatricians and pediatric cardiologists lament that myocarditis—a rare side effect from the mRNA COVID-19 vaccines in adolescents—has been hyped, receiving arguably more attention than the life-saving benefits of the vaccine. Likewise, they say, some physicians who treat adults have minimized the threat that COVID-19 poses to children. Meanwhile, two members of the advisory board that recommended the Food and Drug Administration authorize the vaccine for children between ages 5 and 11 have questioned whether all younger children should be vaccinated before there is more information on the risk of myocarditis.

The mixed messages have left parents feeling confused and uncertain. Although more than one million children ages five through 11 in the U.S. have now been vaccinated, a substantial proportion of parents remain uneasy about it, according to a recent nationwide survey. Shortly before the FDA authorized the Pfizer vaccine for younger children, one in three parents planned to “wait and see” before vaccinating their kids, according to a Kaiser Family Foundation poll. Another 27 percent planned to vaccinate their kids immediately, while 30 percent said they would not vaccinate their kids at all.

Yet review of more than two dozen articles in peer-reviewed medical journals, government documents, and interviews with 10 pediatric cardiologists and pediatricians offer a reassuring picture of the safety of pediatric COVID-19 vaccination. Myocarditis after the vaccine is rarer and usually milder than the cardiac complications from COVID-19, including those from multisystem inflammatory syndrome (MIS-C), says Matthew Elias, a pediatric cardiologist at Children's Hospital of Philadelphia. MIS-C is a serious condition that can occur two to six weeks after an acute SARS-CoV-2 infection in about one out of 3,200 infected children, even if the infection was mild or asymptomatic. MIS-C can involve inflammation of many organs, including the heart, lungs, kidneys, brain, skin, eyes, and digestive organs. The Centers for Disease Control and Prevention reports that more than 5,500 U.S. children have had MIS-C since the pandemic began, though experts believe that’s an underestimate.

“The pediatric hospital experience shows that the risk of patients at any age having cardiac involvement from COVID is uniformly worse than vaccination myocarditis risk,” says Frank Han, a pediatric cardiologist at OSF Healthcare in central Illinois. Like Elias, Han says most vaccine-associated myocarditis cases are mild, without “significant disturbance to the heart function or inability to maintain blood pressure.”

Different types of myocarditis 

Broadly speaking, myocarditis refers to inflammation of the heart and can involve a wide range of symptoms and severity, from very mild pain to heart failure, explains Elias. But different types of myocarditis exist, including three types related to COVID-19: myocarditis from the SARS-CoV-2 infection itself, from COVID-19-triggered MIS-C, and from the vaccine.

Myocarditis during a COVID-19 infection is similar to the classic myocarditis that pediatric cardiologists use to describe what they see with some non-COVID viral infections. But this classic type is more frequent in adults with COVID-19 and rarely occurs in children sick with COVID-19.

What’s far more common in children is either myocarditis from MIS-C, or cardiac symptoms associated with MIS-C that resemble myocarditis. Part of the confusion over pediatric rates of myocarditis related to COVID-19 stem from trying to characterize the cardiac symptoms of MIS-C—whether to call them myocarditis or not—since MIS-C is such a new phenomenom.

What most pediatric cardiologists agree on is that cardiac complications seen with MIS-C are more serious than the myocarditis seen from the vaccine.

Though nearly all children who suffered cardiac problems connected to MIS-C have since recovered, the long-term effects remain unclear. Some children with MIS-C get coronary artery aneurysms, in which a coronary artery widens well beyond what’s considered normal, says Jacqueline Szmuszkovicz, a pediatric cardiologist who specializes in MIS-C at the Heart Institute at Children’s Hospital Los Angeles. Though rare, these aneurysms can sometimes be fatal. They also require long-term follow-up, possibly until adulthood, since they may affect a child’s future risk of coronary artery disease, Han says. Importantly, these aneurysms have been seen with MIS-C but not with the vaccine.

By contrast, one of the first case reports of post-vaccine myocarditis, published in early June, revealed relatively mild characteristics that subsequent research confirmed: Chest pain and shortness of breath are the most common symptoms, sometimes accompanied by a fever. Treatment includes ibuprofen for pain and sometimes steroids or a drug called IVIG that boosts the immune system. Hospital stays typically last a few days, primarily for monitoring. Su says most teens who develop post-vaccine myocarditis probably don’t need hospitalization, but since the phenomenon is new, most clinicians err on the side of caution.

Elias adds that vaccine-related myocarditis is still very stressful for parents. Indeed, two families who spoke with National Geographic described how terrifying it was to see their teen sons hospitalized with chest pain and then restricted from physical activity for several months after they went home. "When we say mild,” Elias adds, “we don’t want to minimize the stress that parents feel when their child is in the hospital.”

Comparing risks of the vaccine and the disease

Many parents want to be able to compare the risk of myocarditis from contracting COVID-19 with the risk of getting it from the vaccine. But experts say that’s difficult to judge.

For starters, one to three cases of myocarditis per 100,000 children and teens typically occur each year unrelated to COVID-19, explains Jennifer Su, director of heart failure and cardiomyopathies at the Heart Institute of Children’s Hospital Los Angeles. Still, researchers estimate that risk is 36 times higher in children under 16 who have had COVID-19, she says. Elias says that about 50 percent of the children he treated with MIS-C have decreased heart function resembling myocarditis, and one study found that 75 percent of 255 patients with MIS-C had myocarditis.

Rates of myocarditis after the vaccine vary by age and sex, with adolescent boys more likely than other groups to experience myocarditis after vaccination. In a study of more than four million mRNA vaccine doses given to adolescents ages 12 though 17, the risk of post-vaccine myocarditis was about one in 16,000 boys and one in 115,000 girls.

No reports of myocarditis after the vaccine have been reported so far in children under 12—the age group at highest risk for MIS-C. The largest and most rigorous peer-reviewed study to investigate myocarditis after vaccination, by a group of Israeli university and government scientists, identifies boys ages 16 to 19 as the highest risk group: one out of 6,637 vaccine recipients of these ages develop myocarditis after the second dose.

Many questions remain about myocarditis from the vaccine, and the CDC has continued tracking and investigating cases. The only known risk factor is being an adolescent male, but it’s not clear why, nor do researchers know if there’s a genetic risk, if a lower vaccine dose reduces the risk, or why the vaccine can cause myocarditis, though several hypotheses exist. It’s also unclear if some small percentage of cases will have long-term effects.

Published research so far shows that nearly all adolescents fully recover, but Michael Portman, director of pediatric cardiovascular research at Seattle Children’s Hospital, is concerned about heart inflammation seen on cardiac MRIs three months later in a few teens who had vaccine-related myocarditis. It may resolve in another three months, but "the jury's still out,” he says, and “we need to find out what happens long term.” Elias likewise says it’s too soon to say if some late inflammation he’s seen in a couple cases will fully resolve, but those cases make up a small fraction of vaccine-related myocarditis.

“I make it really clear that we encounter many more heart issues and more severe heart issues from COVID-19 itself compared to the vaccine,” Elias says.

Regardless, fixating only on myocarditis and ignoring other impacts of the virus doesn’t tell the full story, says Daniel Freeman, a pediatric neurologist in Austin, Texas. He pointed out that one in four children who have died from COVID-19 had no underlying conditions. Then there’s the potential long-term impact of the disease to consider, including neurological effects he has seen.

Further, the risk of MIS-C is that it can involve organs in nearly every major body system. About 60 to 70 percent of children with MIS-C are admitted to the ICU, and one to two percent die. By contrast, vaccine-related myocarditis rarely requires ICU admission and has not resulted in any documented deaths in adolescents.

Aside from MIS-C, COVID-19 is also more serious for children than the flu, with higher rates of ICU admission and intubation and longer hospital stays. Since the pandemic began, COVID-19 has been responsible for 1.7 percent of all deaths in children ages five to 11.

The likelihood that vaccine-caused myocarditis will significantly affect kids’ lives long-term is “just infinitesimally small compared to your risk of getting really sick from COVID,” Su says. “Unfortunately, in this phase of the pandemic, I think the choice is not really to get vaccinated or not, the choice is would you rather get COVID or get the vaccine.”

Brown, the Colorado mother who vaccinated her five-year-old son with a congenital heart defect, accepts that “everything has risks.” She and her husband had already opted for the short-term, rare risks of the procedure to correct his heart condition instead of the lifetime risk of infection-caused endocarditis, a life-threatening inflammation of the heart’s inner lining.

“I saw the vaccine as the same,” Brown says. “We would take the incredibly small risk of a potential short-term vaccine complication over the lifelong, unpredictable and possibly life-ending or life-altering risks of contracting COVID.”