Elizabeth Cooney is a cardiovascular disease reporter at STAT, covering heart, stroke, and metabolic conditions.
In another sign of growing scrutiny over Covid-19 vaccines, the Food and Drug Administration has asked the two makers of mRNA vaccines to widen the age range of boys and young men that their labels say are at risk for a rare side effect causing heart inflammation.
The letters, first reported by CBS News, asked Moderna and partners Pfizer and BioNTech to make updates to safety information based on new studies of myocarditis or pericarditis or both after vaccination. Both reactions are rare and known to occur most often in young men within a week after the second shot in the two-dose Covid-19 vaccine regimen, according to the Centers for Disease Control and Prevention. Most cases were mild, causing no more than brief chest pain.
Safety information was added in 2021, when a CDC advisory panel concluded the benefits of protection against Covid-19 outweighed the risks. Moderna's label now warns of risk in young men ages 18-24, while Pfizer says the same for young men ages 12-17. The FDA letters asked the companies to expand that range to age 16-25 and to cite a 2024 paper funded by the agency in their product information.
Myocarditis, inflammation of the heart muscle, and pericarditis, inflammation of the tissue that surrounds the heart, are driven by an immune system on high alert, set off by inflammatory proteins, research found in 2023. Myocarditis causes fatigue and shortness of breath while pericarditis leads to chest pain.
How high is the risk? A 2022 study reported that the Pfizer vaccines led to an additional 22 myocarditis cases for every million 18- to 29-year-olds in the U.S., while Moderna vaccines led to an additional 31 per million.
Infection with SARS-CoV-2 causes myocarditis at much higher rates than vaccination, with the CDC reporting 150 cases per 100,000 Covid-19 patients.
Steven Nissen, a cardiologist at the Cleveland Clinic, said anything that discourages people from getting Covid vaccinations hurts public health. He called the over-emphasis on a rare disorder related to vaccination misplaced because it poses a far smaller risk than the disease itself.
"You're much more likely to die of Covid than you are to die of myocarditis," he told STAT. "I have buried people from Covid, young people. I lost a 25-year-old nurse to Covid-related myocarditis."
Vaccine-associated myocarditis cases have fallen since the early days of the vaccine rollout, possibly because boosters are given far less frequently than initial vaccinations. In Canada, myocarditis rates from vaccines were lower than in the U.S., which gave the first two mRNA vaccine doses in a tighter time window, Kathryn Edwards, scientific director of the Vanderbilt Vaccine Research Program, told STAT this week.
Since those studies were conducted, vaccine critics like health secretary Robert F. Kennedy Jr. and skepticism from FDA Commissioner Marty Makary have found a forum in Washington. The two letters to the vaccine makers were sent after Makary and Vinay Prasad, who oversees vaccine policy at FDA, said on Tuesday that they plan to limit Covid vaccine boosters to people over age 65 or at risk of becoming seriously ill if infected.
A Senate hearing was convened Wednesday to address myocarditis and other adverse events. It was billed as "The Corruption of Science and Federal Health Agencies: How Health Officials Downplayed and Hid Myocarditis and Other Adverse Events Associated with the COVID-19 Vaccines."