Federal officials have confirmed 323 cases of heart inflammation in people ages 12 through 29 who’ve gotten either the Pfizer-BioNTech or Moderna COVID-19 vaccine, at rates slightly higher than in those who did not receive vaccine.
There were no deaths among the 323, and having COVID-19 remains much more dangerous than the rare side effect, according to data from the Centers for Disease Control and Prevention presented Wednesday to its Advisory Committee on Immunization Practices.
“The facts are clear: this is an extremely rare side effect, and only an exceedingly small number of people will experience it after vaccination,” said a statement co-signed by the Department of Heath and Human Services, the CDC and 15 medical, public health and provider organizations.
The condition, called myocarditis, is a swelling of the heart muscle and can include pericarditis, an inflammation of the outer lining of the heart. Both can cause chest pain, shortness of breath and heart palpitations.
The discovery of the slight increase in cases of myocarditis among young people is an indication of how well the vaccine surveillance system works, said Dr. Grace Lee, a member of the ACIP committee and a professor of pediatrics at Stanford University Medical School.
“There is continuous and ongoing monitoring of vaccine safety for all vaccinations in the U.S.,” she said.
There had been previous reports of slightly higher rates of myocarditis among people who’d received the vaccines. The CDC provided the latest availabledata to its panel Wednesday.
The Pfizer-BioNTech and Moderna vaccines are both two-dose mRNA vaccines. Higher rates of myocarditis have not been reported among those receiving the one-dose Johnson & Johnson vaccine, which is made using a different platform.
The very rare side effect resolved on its own, and patients generally recovered from the symptoms and did well, Dr. Tom Shimabukuro, a member of the CDC’s COVID-19 vaccine safety team,told the panel.
It was more likely to occur in males and was more common after the second dose of vaccine. The majority of cases occurred within a week of vaccination, he said.
Of the 323 confirmed cases of myocarditis as of June 11, 309 were hospitalized and 295 were discharged. The median time for hospitalization was one day, Shimabukuro said.
There were no deaths. Nine people were still hospitalized, and there was no data on the outcome of five patients.
The risk versus reward calculation is obvious, said Dr. Paul Offit, director of the Vaccine Education Center and a professor of pediatrics at Children’s Hospital of Philadelphia, during a post-meeting discussion among vaccine experts.
“This common misconception is that children don’t really suffer from COVID-19 and that you’re taking greater risk from getting vaccinated, he said. “But adults and young adults are commonly being sickened and hospitalized from COVID-19.”
According to the voluntary, self-reporting Vaccine Adverse Event Reporting System, the rate of myocarditis among adolescents 12 through 17 who received a COVID-19 vaccine was 1.8 per 100,000. For boys, it was 3.2 per 100,000.
Adolescents 12 and up have been allowed to get the Pfizer-BioNTech vaccine since May 10. Moderna is authorized only for people 18 and older.
Getting COVID-19 is much more dangerous than the possibility of getting myocarditis, said Dr. Megan Wallace with the National Center for Immunization and Respiratory Diseases.
Among vaccinated boys ages 12 through 17, 56 to 69 myocarditis cases might occur for each million second doses of vaccine, she told the committee.
Among unvaccinated boys in that age group, getting vaccinated would prevent 5,700 COVID-19 cases. That, in turn, would prevent 215 hospitalizations, 71 intensive care unit admissions and two deaths, she said.
Since the beginning of the pandemic, 2,767 adolescents and young adults 12 to 29 years old have died from COVID-19. Since April 1, 316 people in that age range have died.
Committee members expressed concern the myocarditisnumbers might lead to fewer young people getting vaccinated against COVID-19 when adolescents and young adults are an increasing proportion of cases. By May 2021, young people made up 33% of all cases, according to CDC.
The Food and Drug Administration anticipates that it will add a warning sheet to the vaccines about the side effect, so health care providers know to be on the lookout for it, said Dr. Doran Fink in the FDA’s Office of Vaccines Research and Review.