U.S. public-health leaders sought to reassure Americans that COVID-19 shots are safe and to get vaccinated after reports that a relatively small number of mostly young men had suffered a heart problem after being immunized.
About 1,200 cases of heart inflammation have been reported in people who received messenger RNA COVID-19 vaccines, according to the Centers for Disease Control and Prevention. The numbers were reported at a Wednesday meeting of the CDC’s Advisory Committee on Immunization Practices.
After the numbers were made public, top U.S. health officials, regulators and doctors said that the risk potentially posed by shots developed by the Pfizer Inc.-BioNTech SE partnership and Moderna Inc. is extremely low, and that it is much more likely that the coronavirus itself would pose a serious threat to people’s health.
Heightened concern about possible cardiovascular side effects could threaten vaccine uptake among young adults and adolescents just as more of them become eligible to receive shots. The immunization push in the U.S. has been slowing in recent weeks, and dangerous variants have begun to flourish in some undervaccinated areas.
More than 130 million Americans have been fully vaccinated with Pfizer-BioNTech and Moderna shots that use the mRNA technology, according to the CDC, but the Biden administration has struggled to compel younger people to head to the clinic.
The task for health-care providers now will be to bolster confidence in the mRNA shots and highlight the risks of going without a vaccine.
Data presented on Wednesday show there’s a 0.00126% risk of developing the heart condition for those 12 to 39 years old within 21 days of being administered their second dose. Other COVID-caused conditions, like multisystem inflammatory syndrome in children, or MIS-C, pose a greater threat, the agency’s advisers said at the meeting.
“The facts are clear: This is an extremely rare side effect, and only an exceedingly small number of people will experience it after vaccination,” the Department of Health and Human Services, CDC, American Academy of Pediatrics, and other public health leaders said in a statement Wednesday.
The officials said for the young people who do suffer the side effect, most cases are mild and that individuals often recover on their own with minimal treatment. Similar heart problems are more common in patients who get COVID-19, they said.
“Especially with the troubling delta variant increasingly circulating, and more readily impacting younger people, the risks of being unvaccinated are far greater than any rare side effects from the vaccines,” the group said.
Shares of Pfizer were down 1.4% at 3:38 p.m. in New York trading, and BioNTech shares fell 2.5%. Moderna shares were down 3.6%.
The White House said Tuesday that it will not hit its target of administering at least one dose of the vaccine to 70% of Americans by the Fourth of July. The Biden administration’s virus czar, Jeff Zients, attributed the missed goal to young adults.
Less than half of those ages 18 to 24 have gotten their first shot, according to the CDC. Meanwhile only 42% of those ages 16 and 17 have gotten a shot. And among the adolescents most recently cleared for the shot, just 29% have received their first dose.
The Pfizer-BioNTech shot was cleared for those 12 to 15 years old in May. About 2 in 10 adolescents in that age group are now fully vaccinated, according to the CDC. Initial safety findings from the U.S. health agency suggest real-world data is consistent with the results from the companies’ clinical trial prior to authorization.
In the spring, the CDC observed a spike in reports of an inflammation of the heart called myocarditis, and inflammation of the membrane around the heart, or pericarditis, following vaccination.
A total of 1,226 cases have been reported through June 11, according to the CDC, most of which were among young men and adolescents.
“We’re observing this in younger age groups, mainly teens and early 20s,” said Tom Shimabukuro, a safety expert of CDC’s National Center for Emerging and Zoonotic Infectious Diseases, at the meeting.
The risk of heart inflammation following mRNA vaccination in adolescents and young adults ages 12 to 39 is notably higher a few days after the second dose of the vaccine and in men, Shimabukuro said. More data are needed to understand risk factors, treatment and long-term outcomes, according to the advisory committee.
Still, CDC Director Rochelle Walensky said Wednesday that mRNA vaccines have been successful in preventing severe illness and death among young people.
For every million second doses of an mRNA vaccine administered to those 18-to-24-year-olds, the CDC projects 26,000 cases of COVID-19 and 1,657 hospitalizations are prevented, while only 49 to 61 cases of myocarditis may develop.
Speaking at the Milken Institute Future of Health Summit, Walensky added that the data presented at the advisory committee meeting still “overwhelmingly demonstrate that the benefits of vaccination far outweigh the risks.”
Walensky also told the summit that the delta variant is spreading rapidly in the U.S. and now accounts for a fifth of recent coronavirus cases.
The rapid growth in the delta variant, which first emerged in India, was seen after the strain accounted for just 3% of cases analyzed several weeks ago, she added.
(Bloomberg’s Elaine Chen contributed to this report.)