Myocarditis, pericarditis remains rare after COVID-19 booster
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Myocarditis and pericarditis after COVID-19 vaccination is rare across demographic groups and most likely to occur in teen boys in the week after their second shot of a two-dose vaccine, according to a study.
It was also more likely to occur after a booster shot compared with a first dose of vaccine, the study showed.
When it does occur, researchers found the side effect nearly always fades within a week or so, with no further health events noted.
“Overall risk in the general population remains low,” Kristin Goddard, MPH, a research practice specialist at the Kaiser Permanente Vaccine Study Center, told Healio in an email.
“This paper further confirms that myocarditis/pericarditis following [messenger RNA] COVID-19 vaccination is most frequently seen in adolescent males following dose 2 and first boosters,” said Goddard, lead author of the study.
Using data from the Vaccine Safety Datalink, a collaboration of eight integrated U.S. health delivery systems that have tracked specified outcomes of COVID-19 vaccination since shots started being distributed in December 2020, the researchers identified all cases of both conditions reported after primary series vaccine doses and boosters among people aged 5 to 39 years.
From Dec. 14, 2020, through May 31, 2022, the researchers found 320 potential cases of myocarditis/pericarditis 1 to 98 days after vaccination among 6.99 million vaccine doses. Of these, 224 cases were verified; 137 occurred within a week of vaccination, with 18 after the first dose; and 119 after the second dose.
From Sept. 24, 2021, through Aug. 20, 2022, the researchers identified 101 potential cases of myocarditis/pericarditis among 1.85 million booster doses, with 77 of them verified. Of these, 39 cases (51%) were identified in the first week after booster reception compared with 38 identified in the subsequent 13 weeks.
This translated to myocarditis/pericarditis occurring 0 to 7 days after vaccination among people aged 5 to 39 years in about one in 200,000 people after a first vaccine dose, about one in 30,000 people after a second dose and about one in 50,000 people after a first booster dose. The researchers note that incidence varied by age and sex, but there was a disproportionate number of cases in males, specifically after the second dose or a booster.
“Our observed incidence after first boosters was generally higher after the first dose. However, in contrast to some earlier reports, we did not consistently observe a lower incidence after that first booster than after the second dose in the primary vaccination series. ... It is important to keep in mind the overall risk remains small in the general population. These data contribute to an evolving picture of myocarditis and pericarditis following mRNA COVID-19 vaccines,” Goddard said.
As of May 2022, the CDC had investigated 972 suspected cases of myocarditis among children aged 5 to 17 years who received the Pfizer-BioNTech vaccine, with 635 cases confirmed and 214 still under review at that time after a total of 54.8 million doses were administered to people in the age group.
The CDC’s vaccine advisory group in September voted to recommend the new bivalent boosters from Pfizer-BioNTech and Moderna. All but one member of the group voted in favor of recommendation.
A large U.S. study published in April, as well as others in Hong Kong and Israel, have found similarly low risk level for myocarditis, with the highest risk among teen boys — and all, like the new study, have concluded the benefit of vaccination to prevent COVID-19 infection and limit disease severity outweighs the heart risk.
“While myocarditis/pericarditis following vaccination remains unlikely for most, it’s reassuring that when episodes do occur, they tend to be mild, short lived and with full recovery. So far, risk-benefit analyses of COVID-19 mRNA vaccines for all age groups have found that the benefits of vaccination greatly outweigh potential risks,” Goddard said.
References:
- Goddard K, et al. Ann Intern Med. 2022;doi:10.7326/M22-2274.
- CDC. Update on myocarditis following COVID-19 vaccination. https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2022-06-22-23/03-covid-shimabukuro-508.pdf. Published June 23, 2022. Accessed Oct. 7, 2022.
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