The US Food and Drug Administration will now require Covid-19 vaccines from Pfizer/BioNTech and Moderna to use expanded warning labels with more information about the risk of a rare heart condition after vaccination.
The vaccines’ previous labels warned about the risk of a heart condition called myocarditis, inflammation of the heart muscle, and pericarditis, inflammation of the lining outside the heart, which the US Centers for Disease Control and Prevention website says is rare but possible after vaccination. The new labels will expand that warning to certain age groups.
Research has consistently shown that the mRNA Covid-19 vaccines are safe and effective, and millions of people have gotten them without serious incident. Some studies have found that Covid-19 infection itself carries a higher risk of myocarditis or pericarditis than the vaccine does.
The CDC last month told its independent vaccine advisers that research showed Covid-19 vaccinations from 2020 through 2022 showed a statistically significant increased risk of myocarditis. The incidents were rare, however, and “there is no increased risk observed with the doses administered in subsequent years,” the agency said.
In the rare case that someone did develop heart inflammation after vaccination, the CDC told the advisers, acute myocarditis typically resolves quickly.
The vaccines already carried warnings that the highest risk of these heart problems was observed in males between ages 18 and 24 for the Moderna vaccine and 12 to 17 for Pfizer’s; the new warnings for both vaccines will be for males age 16 to 25.
In letters to Pfizer and Moderna that were dated April 17 and are now posted online, the agency says analysis of commercial health insurance claims data shows that there were eight cases of myocarditis and/or pericarditis per million vaccine doses given to people ages 6 months through 64 years.
Cases were more common among males ages 16 through 25 within seven days of vaccination, but they were still rare, with about 38 cases of myocarditis and/or pericarditis per million doses among this group.
A spokesperson for the US Department of Health and Human Services said Wednesday that the move was intended to increase “radical transparency.” Neither Pfizer nor Moderna responded to requests for comment.
The vaccines were developed during the first Trump administration and underwent what the CDC says was “the most intensive safety analysis in US history,” and the agency continues to monitor vaccine administration data for effectiveness and any potential problems.
US Health and Human Services Secretary Robert F. Kennedy Jr., a longtime anti-vaccine activist, has falsely claimed that the Covid-19 vaccine was “the deadliest vaccine ever made.”
In a US Senate Homeland Security and Governmental Affairs subcommittee hearing on Wednesday, Sen. Ron Johnson, R-Wisconsin, claimed that the Biden administration downplayed the risks of the vaccine and delayed getting information about those risks to the public.
One witness, Hawaii Gov. Josh Green, a family physician, said in his testimony the US vaccine safety monitoring systems worked “exactly as intended” by detecting rare cases of myocarditis.
“The data were made public, warnings were updated, and clinical guidance was revised accordingly,” Green said. “Despite this, some continue to promote misleading interpretations, unverified claims or anecdotes to suggest that vaccines are broadly unsafe.”
The FDA has taken recent steps to limit Covid-19 vaccines for certain groups.
On Tuesday, the FDA said it would change the type of evidence it will accept from vaccine manufacturers to approve updated Covid shots, which may limit who is eligible for updated shots. The vaccines are expected to be be available in the fall, but only for adults 65 and older and people with underlying conditions that put them at a higher risk for severe Covid-19 infection.
In an editorial published in the New England Journal of Medicine, FDA Commissioner Dr. Marty Makary and Dr. Vinay Prasad, the new director of the FDA’s Center for Biologics Evaluation and Research, said there’s not enough evidence that healthy children and adults get clinically meaningful benefit from regular Covid-19 shots, and officials want to see more placebo-controlled trials, particularly in adults 50 to 64, before recommending the shots for other groups.
On Thursday, the FDA’s vaccine advisers – the Vaccines and Related Biological Products Advisory Committee – will meet to discuss the coronavirus strain selection for this fall’s Covid-19 vaccines.