The risk for cardiac complications was significantly higher after COVID-19 infection than after mRNA vaccination developed by Pfizer or Moderna against the deadly infectious disease, according to an analysis by the US Centers for Disease Control and Prevention (CDC).

These findings, which were for both males and females in all age groups, supported the continued use of recommended mRNA COVID-19 vaccines among all eligible persons aged over 5 years, the CDC said in its latest weekly Morbidity and Mortality Weekly Report (MMWR).

Cardiac complications, particularly myocarditis - an inflammation of the heart muscle - and pericarditis - swelling and irritation of the thin, saclike tissue surrounding the heart - as well as the multisystem inflammatory syndrome (MIS) - a rare but serious complication of SARS-CoV-2 infection with frequent cardiac involvement and majorly affecting children - have been associated with COVID infection and mRNA vaccination.

Using electronic health record (EHR) data of 15,215,178 persons aged over 5 years from 40 US health care systems from January 1, 2021-January 31, 2022, the investigators calculated incidences of all these cardiac outcomes among all persons.

The results showed that the incidence of cardiac outcomes after mRNA COVID-19 vaccination was highest for boys aged 12-17 years after the second vaccine dose. However, within this demographic group, the risk for cardiac outcomes was 1.8-5.6 times as high after SARS-CoV-2 infection than after the second vaccine dose.

Further, the risk for cardiac outcomes was likewise significantly higher - about 2 to 115 times - after SARS-CoV-2 infection than after the first, second, or unspecified dose of mRNA COVID-19 vaccination for all other groups by sex and age.

"Analysis of EHR data from 40 US health care systems found that the incidences of cardiac complications after SARS-CoV-2 infection or mRNA COVID-19 vaccination were low overall but were higher after infection than after vaccination for both males and females in all age groups," said corresponding author Jason P. Block, Department of Population Medicine, from Harvard Medical School, US.

The team also cited two studies from Israel and the UK that showed a similar higher risk for myocarditis after SARS-CoV-2 infection compared with that after mRNA COVID-19 vaccination.