Social media posts misrepresent myocarditis risks

CLAIM: Patients who have myocarditis have a very high chance of dying within 10 years.

AP’S ASSESSMENT: False. Claims that patients with myocarditis, a condition where the heart muscle is inflamed, have a very high mortality rate come from a misreading of decades-old data that focused only on the most ill patients. Furthermore, while health officials say myocarditis may be an extremely rare side effect of the COVID-19 vaccine for young people, severe cases are even more unlikely.

THE FACTS: Very rarely, teens and young adults given the Pfizer vaccine or a similar one made by Moderna experience a serious side effect, heart inflammation, or what doctors call myocarditis. It’s mostly in young men or teen boys, and usually after the second dose. They tend to recover quickly, and after intense scrutiny U.S. health authorities concluded the vaccine’s benefits outweigh that small risk, The Associated Press reported.

“The facts are clear: this is an extremely rare side effect, and only an exceedingly small number of people will experience it after vaccination. Importantly, for the young people who do, most cases are mild, and individuals recover often on their own or with minimal treatment,” read a statement issued last June by top U.S. government health officials, medical organizations, laboratory and hospital associations.

Children ages 5 to 11 can now receive a kid-sized shot of Pfizer’s COVID-19 vaccine. Many experts predict the potential risk of vaccine-induced myocarditis in children under 12 will be even lower, due to the smaller size of the dose and the fact that myocarditis caused by infections or medication is more common in males past puberty.

But this week, social media posts misrepresented the risks associated with vaccine-induced myocarditis including in children and falsely suggested the condition was likely to cause death.

“If a five year old develops ‘mild myocarditis’ there is a 50/50 chance they won’t live to see their 15th birthday,” a false post published on Tuesday claimed. “This is what we are doing to our CHILDREN for political statement.” The post included an image from the text of a scientific paper that reads: “Non-fulminant active myocarditis has a mortality rate of 25% to 56% within 3 to 10 years, owing to progressive heart failure and sudden cardiac death.”

Another Facebook post first circulated on Monday falsely claimed that myocarditis “is literally a slowly progressing death,” and that deaths would “come years later at an extremely high mortality rate of a quarter to half of all cases.”

But pediatric cardiologists The Associated Press spoke with said the claims were false and distorted the scientific literature.

Dr. Matthew Oster, a pediatric cardiologist studying myocarditis with the CDC COVID-19 vaccine task force, said in an email to the AP that the posts were a “misinterpretation” based on data from a decades-old study that “is not applicable to those with myocarditis after COVID-19 vaccine for a number of reasons.”

The data quoted by one of the posts was referencing in part a 1995 study that only included patients with significant heart failure, Oster said, adding that the average age in that study was 42. That’s much older than the average age of those with myocarditis after receiving COVID-19 vaccines, Oster said.

Dr. Leslie Cooper, who studies myocarditis and serves as the chair of the department of cardiovascular medicine at Mayo Clinic in Florida, echoed this assessment. Cooper said the claim that heart issues would occur years after vaccination is not supported by any data.

“The quotation that individuals with non-fulminant active myocarditis have a mortality rate of 26% to 56% within three to 10 years is drawn from hospitalized people with heart failure and cardiomyopathy, who are the sickest percentile of people with myocarditis,” Cooper said in reference to the data quoted in the post.

“The vast majority of people who present with myocarditis are not that sick,” Cooper said.

Cooper also said COVID-19 vaccines are safe and that the risk of developing myocarditis after receiving them is low.

“Everything that we know about this vaccine is that it is a very well tolerated vaccine that has an exceptionally low rate of adverse events.” Cooper said. “Many millions of people have received the mRNA COVID vaccines. And of all of those, there have been less than 1,000 reported cases of myocarditis in hundreds of millions of vaccines.”

Even when individuals did develop myocarditis after receiving the vaccine, the condition was mild and recovery was quick in the vast majority of cases, according to Cooper.

“Vaccine associated myocarditis is a relatively mild condition,” Cooper said, adding that heart failure was very rare. When cardiomyopathy, a condition in which the heart is unable to pump blood effectively, occurs in very rare cases, “the recovery rate within 2 weeks is substantial,” said Cooper.

He also cited an Israeli study tracking individuals who had COVID-19 vaccine related myocarditis in which 76% of individuals had mild cases, 22% had moderate cases and only one case was associated with cardiogenic shock, meaning the heart could not pump enough blood.

Because the vaccine has just been rolled out, long term data doesn’t exist just yet. So definitive claims about what will happen years down the road aren’t based on evidence or fact.

“The vaccine has only existed for one year,” said Cooper, who added that while no direct data exists to support or refute the claim that individuals would die years after developing myocarditis from the vaccine, “any reasonable interpretation of historical data does not support that conclusion.”

“We know that in children and adults, most cases are relatively mild, and resolve without any long term consequence,” he said.

Furthermore, a study published in the New England Journal of Medicine in August that analyzed data in people 16 and older, found myocarditis caused by COVID-19 infection is far more common than vaccine-associated myocarditis.


This is part of AP’s effort to address widely shared misinformation, including work with outside companies and organizations to add factual context to misleading content that is circulating online. Learn more about fact-checking at AP.