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May 26, 2023
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Myocarditis, pericarditis incidence low across 10 million doses of mRNA COVID-19 vaccines

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Key takeaways:

  • A rapid cycle analysis identified 178 potential cases of myocarditis/pericarditis among Veterans Health Administration patients.
  • Thirty-three of these cases were confirmed to be related to a COVID-19 vaccine.

The incidence of myocarditis/pericarditis among veterans was low across more than 10 million doses of messenger RNA COVID-19 vaccines, given as a primary or booster dose, administered at the Veterans Health Administration, researchers found.

“We conducted this study because we were interested in estimating the incidence rate of myocarditis, pericarditis and myopericarditis following a COVID-19 mRNA vaccine across the Veterans Health Administration (VHA),” Jing Luo, MD, MPH, assistant professor of medicine at the University of Pittsburgh School of Medicine, told Healio.

IDN0523Luo_Graphic_01_WEB
Luo J, et al. Open Forum Infect Dis. 2023;doi:10.1093/ofid/ofad268.

“These are clinically significant adverse events that have been reported across several other settings but not previously reported in VHA. Further, VHA’s Center for Medication Safety is required to conduct surveillance activities for a wide range of potentially serious adverse events following vaccinations, including myocarditis risk,” Luo said.

Jing Luo

To assess rates of confirmed myocarditis/pericarditis following mRNA COVID-19 vaccines, Luo and colleagues evaluated a cohort of all adults administered one or more mRNA COVID-19 vaccines, including boosters, in the VHA between Dec. 14, 2020, and Oct. 9, 2022.

According to the study, all potential cases of myocarditis/pericarditis identified underwent in-depth chart review and case validation by a team of pharmacists and expert clinicians. The main outcome of the study was the incidence rate of confirmed myocarditis/pericarditis among vaccine recipients within 21 days of either a first, second or booster dose of a mRNA COVID-19 vaccine.

Between Dec. 14, 2020, and Oct. 9, 2022, 3,877,453 doses of the Pfizer-BioNTech vaccine and 4,221,397 doses of the Moderna vaccine were administered as first or second dose, and 1,012,561 of Pfizer-BioNTech booster doses and 1,156,160 of Moderna booster doses were administered.

Through their analysis, the researchers identified 178 potential cases of myocarditis/pericarditis among vaccinees of any age and 22 potential cases among patients aged 18 to 39 years. The researchers confirmed 33 of the cases — including six cases among 18- to 39-year-olds — corresponding to an overall incidence rate ranging from 0.46 per million (95% CI, 0.01-2.55) for one dose of Moderna to 6.91 per million (95% CI, 2.78-14.24) for a Pfizer booster shot.

Among patients aged 18 to 39 years, incidence rates ranged from 7.1 (95% CI, 0.18-39.56) for the second dose of Moderna to 19.76 (95% CI, 5.38-50.58) for the second dose of Pfizer.

According to the study, patients with confirmed cases began experiencing symptoms an average of 3 days after receiving a vaccine, and all symptoms resolved within 30 days.

“Although the rapid cycle analysis initially identified 178 potential cases of myocarditis/pericarditis, only one out of five cases were confirmed to be related to a COVID-19 vaccine after chart review,” Luo said. “These findings highlight the paramount importance of both active surveillance and chart validation for rare but serious adverse events related to COVID-19 vaccines.”