Heart Inflammation Is More Common From COVID-19 Infection Than Vaccines, Study Finds

Throughout the pandemic, Guillermo Torre-Amione, MD, PhD has treated patients for myocarditis, a rare inflammation of the heart which can result from COVID-19, and in few cases, the vaccine. 

When comparing case numbers, Torre-Amione notes that significantly more of his patients have come down with the condition from the virus itself than from the vaccine.

A recent study published in the New England Journal of Medicine has evaluated this trend nationwide and found that myocarditis risk associated with COVID-19 itself is much higher than with the vaccines.

Notably, researchers found that the vaccines increased the risk of myocarditis, with about three events per 100,000 people, but the virus posed a higher risk of 11 events per 100,000 people. The condition is not unique to COVID-19 and has also been associated with other viral illnesses.

“The numbers were really significantly different. They were more in favor of vaccines,” Torre-Amione, chairman of Cardiol Therapeutics, tells Verywell.

A small number of people reported myocarditis or pericarditis, an inflammation of the heart lining, in the days following an mRNA vaccination. The data prompted the Food and Drug Administration to issue a warning of the conditions on Pfizer’s and Moderna’s mRNA COVID-19 vaccines.

But health authorities have maintained that the benefits of vaccination outweigh the risks.

Torre-Amione, who practices at hospitals in Texas and in Monterrey, Mexico, says that about a quarter of the COVID-19 patients in the Mexico hospital had documented cardiac injury, which includes myocarditis and other conditions. He has yet to see official studies on whether or not the different sources would increase the severity of the condition.

“My gut feeling would be that vaccine-induced myocarditis is a much milder condition, where people would tend to recover quickly,” Torre-Amione says. 

COVID-19 can also trigger other health problems that could lead to myocarditis as a secondary result of the virus, he adds.

Side Effects From the mRNA Vaccines

The new study evaluated a wide range of serious side effects from the virus and the vaccines. Among the health risks studied, the COVID-19 vaccines did not create an elevated risk for most of the conditions except for myocarditis. 

The Pfizer vaccine slightly increased the risks of appendicitis, shingles, and swollen lymph nodes, which were not associated with COVID-19 infection. COVID-19 patients, however, had a higher risk of developing serious conditions like acute kidney injury, heart attacks, and blood clots.

Risks of appendicitis and swollen lymph nodes were noted in Pfizer’s Phase 3 trials, which the company presented when it applied for permission to extend the vaccine’s emergency use authorization to people aged 12 and above. 

In the Phase 3 trial, 0.6% of 12 to 15 years olds reported having swollen lymph nodes. All of the cases took place between two and 10 days after their vaccination, and half of these cases were resolved within 10 days, according to Pfizer.

Shingles and myocarditis were not listed as side effects studied in the Phase 3 trial. 

Researchers also noted that Bell's Palsy is a potential side effect of the mRNA vaccines, having found an increase in chances of developing the condition in the days following vaccination. This finding is in contrast to an FDA briefing, which said there was no elevated risk of Bell’s Palsy associated with Pfizer's COVID-19 vaccine.

Should You Worry About Myocarditis Risks?

Myocarditis risks associated with the mRNA vaccines are rare. Confirmed cases of myocarditis have mostly occurred among male adolescents and young adults aged 16 and above, according to the Centers for Disease Control and Prevention.

Torre-Amione says people can recover from myocarditis, as have many of his patients. People who develop myocarditis after the vaccine will typically see symptoms within two weeks of their second dose. While the timeframe for when and if someone will develop myocarditis after contracting COVID-19 is unclear, Torre-Amione expects it is likely also a short window.

“My hunch will be that if you don't see this within the first four weeks, you're not likely to see it,” he says.

Still, myocarditis should not be taken lightly, as a severe case can lead to heart failure. Continuing to carefully monitor, research, and study the condition will be crucial for a potential vaccine approval for children younger than 12 since the condition has been reported more commonly in younger individuals, Torre-Amione says.

Hanoch Patt, MD, MPH, a pediatric cardiologist at Pediatric & Congenital Cardiology Associates in Austin, Texas, says that the COVID-19 virus poses more harm to children than the vaccine.

Patt suspects the risk of vaccine-associated myocarditis for children will likely be lower than that in young adults because the risk of myocarditis generally increases at age 15 and decreases after young adulthood. He also adds that it is important to wait for more data to come out.

Virus-induced conditions like Multisystem Inflammatory Syndrome in Children (MIS-C) can be “much more severe than vaccine-associated myocarditis,” Patt writes to Verywell. MIS-C can lead to long-standing heart changes and organ damage, he adds. 

The CDC currently has dedicated a team to study and learn more about the condition. 

“The biggest side effect of the vaccine is the fear of using it, and not putting into context the small risks from the vaccine versus the significant risks associated with COVID-19 infection,” Patt says.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.