(Adds background from presentation)
By Michael Erman and Manojna Maddipatla
June 10 (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 U.S. Centers for Disease Control and Prevention (CDC) said on Thursday.
More than half of the myocarditis or pericarditis cases reported to the U.S. 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 https://www.fda.gov/media/150054/download to an advisory committee to the U.S. 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.
Israel’s Health Ministry has 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.
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.
(Reporting by Michael Erman in Maplewood, N.J. and Manojna Maddipatla in Bengaluru; Editing by Bill Berkrot)