Are there long-term risks of myocarditis?
Of the hundreds of millions of Covid vaccine doses given in the U.S. since late 2020, there have been around 1,000 reports of vaccine-related myocarditis or pericarditis in children under age 18, primarily young males, according to the Centers for Disease Control and Prevention. Most of those who developed the condition have fully recovered, although research so far has only looked at how well they’re doing after several months. Some doctors wonder if it can cause permanent damage to the heart.
Now, the first research in the U.S. is underway, tracking adverse health effects — if any — that may appear in the years following a diagnosis of vaccine-associated heart problems. Moderna has already launched two trials, the most recent in September. Pfizer confirmed that at least one of its trials, which will include up to 500 teens and young adults under age 21, is slated to begin in the next couple of months.
The Food and Drug Administration has required that the drugmakers conduct several studies assessing the potential long-term impacts of myocarditis, as part of its approval of the mRNA Covid vaccines in the U.S. Early findings from the research could be published as early as next year, sources told NBC News.
Some of the trials will follow those who developed the condition for as long as five years, according to the FDA’s approval letters.
What is known about myocarditis and vaccines?
The vast majority of cases occur in young men, ages 16 to 24, according to the CDC. The agency did not have data available on the total number of cases in young adults 24 and younger, but it estimates there have been 52.4 cases and 56.3 cases per thousand doses of Pfizer’s and Moderna’s vaccines, respectively.
Symptoms of myocarditis include:
- Chest pain
- Shortness of breath
- Feelings of having a fast-beating, fluttering or pounding heart
A study by Canadian researchers published Monday in the Journal of the American College of Cardiology found that men younger than 40 who got the Moderna vaccine had the highest risk of heart issues, usually within 21 days after the second dose.
Last month, Kaiser Permanente scientists found that incidences of myocarditis following a booster dose of either the Pfizer or the Moderna vaccine were higher than after the first dose.
There has not been a similar reporting pattern observed after receiving the Johnson & Johnson vaccine. Novavax has said no heart inflammation concerns were raised during clinical trials of its vaccine.
In some cases, people who’ve developed myocarditis after a viral infection can suffer scarring along the heart’s tissue, reducing its ability to pump blood and circulate oxygen around the body, said Dr. Leslie Cooper, the chair of the department of cardiology at the Mayo Clinic in Rochester, Minnesota. Cooper joined an expert advisory panel formed by Moderna to monitor its Covid vaccine safety.
It’s unknown how many people with vaccine-associated myocarditis will experience this scarring, he said.
“It could be 2%. It could be 0%. It could be 20%,” he said, referring to the percentage of people with vaccine-associated myocarditis who could experience long-term heart consequences. “We don’t know the answer.”
The CDC recently published a study in The Lancet that looked at health outcomes in more than 500 teens and young adults at least 90 days after the onset of myocarditis following an mRNA vaccination.
