In October 2021, Da’Vion Miller was found unconscious in the bathroom of his home in Detroit a week after receiving his first dose of Pfizer’s Covid vaccine.
He had known something was wrong: Then 22, he had started experiencing chest pain two days after getting vaccinated, followed by fatigue, shortness of breath and dizziness.
Miller was rushed to Henry Ford West Bloomfield Hospital, where he was diagnosed with myocarditis, an inflammation of the heart muscle, and pericarditis, an inflammation of the outer lining of the heart. His doctor advised him not to receive a second dose of either the Pfizer or the Moderna vaccines.
“I was like, that’s crazy,” Miller said, noting that he knows the heart inflammation condition following vaccination is extremely rare.
Miller is one of a very small group of people in the United States who have experienced myocarditis following vaccination with the Pfizer-BioNTech or the Moderna Covid vaccines based on mRNA technology.
Myocarditis is a condition that has long been linked to a number of viral infections, including influenza, coxsackieviruses, as well as Covid. It has also been observed as an infrequent but worrisome side effect of the mRNA Covid vaccines.
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. The trials will be monitoring for myocarditis and subclinical myocarditis, which doesn’t cause symptoms.
The FDA declined to comment on Pfizer’s and Moderna’s studies because they are ongoing, but an agency official said the chance of having myocarditis occur following vaccination is “very low.”
The condition does not lead to cardiac-related death, the official said, as claimed by Florida’s surgeon general last month who cited an unpublished analysis of state data.
“There is no evidence of increased risk of deaths following mRNA vaccines compared to individuals who did not get vaccinated,” the official said. “In fact, evidence from well-conducted, peer-reviewed, published studies suggests that the risk of death is higher for unvaccinated individuals for nearly every age group.”
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 million doses of Pfizer’s and Moderna’s vaccines, respectively.
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. The study was observational, meaning it doesn’t prove cause and effect but it is one of only a few studies to compare the risk of myocarditis between the Pfizer and the Moderna vaccines.
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, but still lower than after the second.