Experts Say Link Between Heart Inflammation and COVID Shot Unlikely

Health officials in Israel are looking into a few reports of heart inflammation in people who received a COVID-19 vaccine, but experts say that a link between the condition and the shot is not likely.

In late April, Israel's pandemic response coordinator Nachman Ash said that a preliminary study had found "tens of incidents" of a type of heart inflammation called myocarditis in people who received Pfizer’s COVID-19 shot. Israel’s Health Ministry has yet to draw any conclusions from the reports.

The rare condition was found mostly in younger people and occurred after their second dose of the vaccine. The cases represent only a small percentage of the more than five million people who have gotten the COVID vaccine in Israel.

Ash said that determining a link between heart inflammation and the Pfizer vaccine would be challenging because myocarditis can be caused by a variety of viruses. He also pointed out that a similar number of myocarditis cases was reported in prior years—suggesting that it's not unusual for the condition to occur in the general population.

What Is Myocarditis?

Myocarditis is inflammation of the heart muscle (myocardium) that weakens the heart’s ability to contract normally. It’s often caused by viral infections, including influenza and the virus that causes the common cold. 

“You can also see myocarditis in autoimmune diseases like lupus, or anything that causes the body to go a little bit off the rails and start attacking its own cells,” John Sellick, DO, an infectious diseases professor at the University at Buffalo’s Jacobs School of Medicine and Biomedical Sciences, tells Verywell. "There are some medications that are used for chemotherapy that cause myocarditis, too.”

Some people have only mild symptoms and recover in a few weeks. People with more severe symptoms can have chest pain and shortness of breath. While these serious cases can cause heart damage or even death, most people recover from myocarditis with the right treatment.

No Indication of a Link to Vaccines

In the United States, 14 cases of heart inflammation were reported among people who got the COVID-19 vaccine through the military's health services. The Centers for Disease Control and Prevention (CDC) is working with the Department of Defense to investigate the cases but has not identified a link between heart inflammation and the COVID-19 vaccine.

Experts do not see the few reported cases of myocarditis in people who have gotten a COVID vaccine as a reason for concern—and they don't think that people should avoid the vaccine.

“The U.S. recently reported that they've been doing active surveillance for months to see if there are reports of heart inflammation that follow vaccination, and they have not seen reports outside of what's expected in the general population,” Christopher Newton-Cheh, MD, a cardiologist and cardiovascular geneticist at Massachusetts General Hospital, tells Verywell. “Heart inflammation existed long before COVID was circulating in the world, and we expect it to continue to occur.”

The European Medicines Agency’s safety committee recently met to review vaccine safety reports and said that “there is no indication at the moment” that cases of heart inflammation “are due to the vaccine.”

The committee has asked that mRNA vaccine makers provide more data on these events (including the ages and genders of those who developed the condition) and said that it will report any additional findings.

Sellick says that with millions of doses of Pfizer’s COVID-19 vaccine having been administered in the U.S. if there was a significant concern between the shot and heart inflammation, we likely would have seen it by now.

“So even if there were a relationship, when there's 50 or 100 cases out of 200 or 300 million doses, the risk is absurdly low," Sellick says. "Certainly much lower than the risk that you would have if you were to get COVID."

More Info on Cases Needed

According to Sellick, we can't make any conclusions without more information on the reported cases of heart inflammation in vaccinated people, including a thorough investigation into their health—especially with regard to any previous or underlying conditions that they have. This information would paint a fuller picture, particularly if they had another viral infection or health issue. 

Sellick and Newton-Cheh both say that heart inflammation from an mRNA vaccine is highly unlikely. “I can never say it's impossible, but it just doesn't seem plausible," Sellick says.

Newton-Cheh explains that Pfizer’s mRNA vaccine contains a genetic code of the coronavirus’s spike protein that instructs your body’s cells to produce an immune response—but it does not actually infect you with a weakened version of the virus.

“That protein by itself is not able to lead to the production of virus,” Newton-Cheh says, adding that heart inflammation would be unlikely to results from an mRNA vaccine.

While there is ongoing research into some evidence of heart inflammation in people with COVID-19, Newton-Cheh says that it appears to be a rare occurrence.

Stay Informed and Get Vaccinated

The cases of myocarditis in Israel are not the first vaccine-related health news event in recent weeks so it's understandable that people have concerns. However, experts say that people should not be worried about heart inflammation and mRNA vaccines.

Newton-Cheh says that it's a good thing that health agencies are monitoring the reports closely. Large amounts of data mean that officials are keeping a close watch on any outcomes following vaccination. 

That said, as the pandemic and vaccination efforts continue, the pressure is on scientists and public health officials to share these reports in a way that's helpful rather than harmful.

“One of the challenges of communicating to the public about the value of vaccines is that most people are not used to weighing noisy data. And so when they hear an anecdote—I heard about someone who got sick after they got the vaccine—that plays a really large role for that one individual in their decision making," Newton-Cheh says. "It's what we try to avoid doing in the scientific or medical community by being pretty rigorous about carefully evaluating what the likely rates are."

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.