Cardiac complications after COVID infection or vaccination are rare but possible, the CDC says—but they’re much more likely after infection

While cardiac complications are possible following both COVID infection and vaccination, they’re significantly more likely to occur after infection, the U.S. Centers for Disease Control said Friday, in a continued push to vaccinate all eligible Americans.

The organization cited a new study, included in its weekly morbidity and mortality report, that examined the electronic health records of millions of patients at 40 U.S. health care systems between Jan. 1, 2021, and Jan. 31 of this year.

Among the findings: Young males ages 12-17 saw the highest incidence of cardiac events, during a post-vaccine window, among vaccinated individuals. However, the risk of the same group experiencing a cardiac event after infection was 1.8-5.6 times higher, depending on the window of time and particular complication, according to the study, which defined cardiac events as myocarditis, pericarditis, or Multisystem Inflammatory Syndrome (MIS).

Rates were similar in males ages 18-29, with cardiac events higher after the second dose of the vaccine than the first, but just a fraction of what occurred after infection: 6.5-15 per 100,000 compared to 55-100 per 100,000.

Researchers found that females ages 5-11 had no cardiac events after receiving the vaccine but anywhere from 5.4-94.2 incidents per 100,000 after infection. While the incidence of cardiac events in women 18-29 after vaccination was larger—anywhere from .5 to 10.9 per 100,000—the incidence typically paled in comparison to cardiac events after infection, which reached as high as 79.6 per 100,000.

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