Heart inflammation cases higher than expected after mRNA COVID-19 shots

Preliminary findings from two vaccine safety monitoring systems suggest a higher-than-expected number of cases of heart inflammation after the second dose of mRNA COVID-19 vaccines in young men.

A medical worker holds a syringe with Sputnik V (Gam-COVID-Vac) vaccine against the coronavirus disease (COVID-19) before administering an injection at a vaccination centre in a shopping mall in Saint Petersburg, Russia February 24, 2021. (photo credit: REUTERS)
A medical worker holds a syringe with Sputnik V (Gam-COVID-Vac) vaccine against the coronavirus disease (COVID-19) before administering an injection at a vaccination centre in a shopping mall in Saint Petersburg, Russia February 24, 2021.
(photo credit: REUTERS)
Preliminary findings from two vaccine safety monitoring systems suggest a higher-than-expected number of cases of heart inflammation after the second dose of mRNA COVID-19 vaccines in young men, the US Centers for Disease Control and Prevention (CDC) said on Thursday.
More than half of the myocarditis or pericarditis cases reported to the US Vaccine Adverse Event Reporting System after patients had received either the Pfizer/BioNTech or Moderna vaccines were in people between the ages of 12 and 24, the CDC said. Those age groups accounted for less that 9% of the doses administered.
"We clearly have an imbalance there," Dr. Tom Shimabukuro, deputy director of the CDC's Immunization Safety Office, said in a presentation to an advisory committee to the US Food and Drug Administration that is meeting on Thursday.
He said that the Vaccine Safety Datalink (VSD) - another safety monitoring system - showed an increased incidence of the heart inflammation in 16 to 39 year olds after their second dose of the shots when compared to the rate observed after their first dose.
The limited data shows that most of the patients - at least 81% of them - had a full recovery from their symptoms, Shimabukuro said.
Pfizer and Moderna were not immediately available for comment.
The CDC said it will hold a meeting of its Advisory Committee on Immunization Practices next week to further evaluate the evidence and assess the risk of myocarditis following mRNA vaccination for COVID-19.
Earlier this month, Israel’s Health Ministry said it found a likely link to vaccination in a small number of myocarditis cases observed mainly in young men who received Pfizer’s COVID-19 vaccine.
After the Health Ministry received reports on some cases diagnosed close in time after a coronavirus vaccination, a committee of experts was appointed to look into the issue. The committee included public health experts specialized in epidemiology, members of the National Center for Disease Control and academics from the Tel Aviv University, Technion-Israel Institute of Technology and Haifa University.
The committee considered all the myocarditis cases between December, when the vaccination campaign started, and May.
Out of the 275 cases reported in the period, some 148 occurred in the aftermath of a dose of the coronavirus vaccine – 27 cases out of 5,401,150 recipients of the first dose and 121 within 30 days after the second dose (out of 5,049,424). Some 11 patients of the former and 60 of the latter suffered from preexisting conditions).
Many of the cases were reported among men 16-30, and especially ages 16-19. In addition, most of the patients were discharged from the hospital in less than four days, and 95% of the cases were considered mild.