Soon after the first COVID-19 vaccines appeared in 2021, reports of rare cases of heart inflammation, or myocarditis, began to surface.
In most instances, the myocarditis has been mild and responded well to treatment, though up to four potentially mRNA vaccine-related deaths from myocarditis in adults have been reported worldwide. No known verified deaths of children have been reported based upon publicly available data. The exact number remains a topic of very heated debate because of variability in the reporting of possible myocarditis-related deaths.
Studies have largely confirmed that the overall myocarditis risk is significantly higher after an actual COVID-19 infection compared with vaccination, and that the prognosis following myocarditis due to the vaccine is better than from infection.
As pediatric cardiologists, we specialize in heart issues relevant to kids of all ages. We believe it is important to weigh the risk of myocarditis caused by COVID-19 immunization against not only viral myocarditis from COVID-19, but also all the other complications that COVID-19 can lead to.
Comparing risks of myocarditis from severe disease versus COVID-19 vaccination or infection is difficult to do well, and debate continues over which of those outcomes poses a higher risk.
Myocarditis is any condition that causes heart inflammation. Most cases of myocarditis are caused by infections, particularly viral ones.
A mistaken assumption is that all myocarditis is severe, since it implies damage to the heart. However, mild cases in which there is very little swelling and only temporary damage to the heart are more common than severe cases that require a machine to support heart function.
Vaccination vs. infection risk
The challenge of parsing risks of myocarditis from viral infection compared with COVID-19 vaccination is due in part to the difficulty of establishing a diagnosis of myocarditis and its population rates accurately.
The United States Vaccine Adverse Event Reporting System, or VAERS – which is an initial reporting system for vaccine side effects – is by itself inadequate to determine the rate of any vaccine-associated side effect. This is because any side effect can be reported, and verification of a reported event only takes place afterward by the Centers for Disease Control and Prevention.
That vetted data is then reported in more robust databases like the Vaccine Safety Datalink.
Thankfully, severe myocarditis after mRNA vaccination for COVID-19 is extremely rare. A 2021 study from Nordic scholars, which looked at comparative risks of myocarditis and heart arrhythmia in patients who experienced myocarditis after COVID-19 infection versus immunization found that the risks vary significantly by age group.
This has been touted as a reason not to vaccinate healthy young men against COVID-19. The follow-up study, however, found that the comparative risks of negative outcomes were worse from myocarditis from COVID-19 infection and other viral myocarditis than from vaccination in all patients older than 12 years of age.
And it’s worth noting that, as of mid-March 2023, the U.S. still leads the world in COVID-19 hospitalizations.
Myocarditis risk by age and gender
A survey of all currently available research reveals that the risk of myocarditis after COVID-19 vaccination is highest in young men between the ages of 18 and 39 and older teen boys in the age range of 12 to 17, with the highest risk after the second dose of vaccine. The cause appears to be related to how the immune system processes the mRNA and sometimes generates an excessive immune response.
Myocarditis risk related to COVID-19 immunization is markedly lower in children younger than 12 years of age and much lower in adult males older than 50. The risk of severe disease from COVID-19, particularly in those older than 50 years, has been far higher throughout the pandemic than the risk of myocarditis from COVID-19 vaccination. The risk of vaccination myocarditis is uniformly lower in girls than in boys.
How to parse the risks
While the risks of myocarditis have been highest in teen boys and young men regardless of cause, the severity and outcome of myocarditis was much worse at the 90-day mark when it stemmed from COVID-19 infection or other viral diseases. This mirrors our team’s research on this same topic.
This discussion also doesn’t take into account the clot and heart attack risks from COVID-19 itself. Because COVID-19 damages blood vessels in all parts of the body, some organ damage such as kidney failure, blood clots, heart attacks and strokes can occur.
We recognize a need for more research into how people fare over the medium and long terms following a case of immunization-related myocarditis. This is why research is ongoing.
COVID-19 risks in children
While there have been far fewer deaths from COVID-19 in children than adults, COVID-19 is still one of the leading causes of childhood death in the U.S., based on an early 2023 study. But COVID-19 deaths are not the only relevant measure of its effect in kids. COVID-19 has also killed more children in a shorter time period than several other vaccine-preventable diseases, such as hepatitis A and meningitis before the availability of their vaccines.
The argument that some have made that fewer children than adults die from COVID-19, or that it is often mild in children, has never been an acceptable justification to not do everything possible to protect children from it.
The primary risk that COVID-19 presents now to children is long COVID, followed by the risk of severe disease. The estimated percentage of children acquiring long COVID is still being debated, but the symptoms from long COVID can be extraordinarily debilitating.
Weighing the decision to vaccinate
We believe that the decision of whether to vaccinate against COVID-19 should be based upon the patient’s age, other health problems, relative risk from vaccines, how much and what type of COVID-19 is in your community and the patient’s and family’s preference.
Adults who are immunocompromised or have other medical problems known to worsen COVID-19 disease severity still carry the highest risk of severe disease. They should therefore follow the CDC COVID-19 vaccination schedule with additional boosters, if advised by their physician.
While COVID-19 immunizations are not as efficient at preventing viral transmission now as they were with the earliest variant, they remain highly effective at reducing severe illness and hospitalization, even in kids and particularly in the high-risk state of pregnancy.
Frank Han, M.D., is assistant professor of pediatric cardiology, University of Illinois at Chicago. Jennifer H. Huang, M.D., is associate professor of pediatric cardiology, Oregon Health and Science University. This piece originally appeared in The Conversation, a nonprofit news source dedicated to unlocking ideas from academia for the public.
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