Myocarditis risk higher after Covid infection than Pfizer or Moderna vaccination, CDC finds

People infected with Covid-19 face a higher risk of myocarditis and other inflammatory heart conditions than those vaccinated against the disease, according a large study published by the Centers for Disease Control and Prevention on Friday.

The CDC found the risk of myocarditis, pericarditis and multisystem inflammatory syndrome was higher after Covid infection than after Pfizer or Moderna vaccination in males and females ages 5 and older. However, these cardiac conditions are rare after infection and vaccination alike, according to the CDC.

Myocarditis is an inflammation of the heart muscle and pericarditis is an inflammation of the outer heart lining. Multisystem inflammatory is a condition associated with Covid infection that affects multiple organ systems.

Pfizer and Moderna’s vaccines have been associated with an elevated risk of myocarditis and pericarditis after the second dose, particularly among boys ages 12- to 17-years-old. However, even in this group the risk of myocarditis and pericarditis was higher after Covid infection than after vaccination, according to the CDC.

Among teenage boys, the rate of myocarditis or pericarditis after infection was at least 50 cases per 100,000 people, compared to at least 22 cases per 100,000 after the second vaccine dose. The overall risk of heart conditions after Covid infection was up to 5.6 times higher compared to the second vaccine dose. The risk was up to 69 times higher after infection compared to the first shot.

The CDC examined the electronic health records of more than 15 million people ages 5 and older across 40 health-care systems from Jan. 2021 through Jan. 2022. Scientists studied the risk of developing a cardiac condition after a Covid infection compared to the first and second doses of Pfizer and Moderna’s vaccines. The study excluded booster doses from the comparison.

Overall, the risk of a heart issue after Covid infection was anywhere from 2 to 115 times higher compared to vaccination depending on age, gender and the dose administered.

In February, the CDC said males age 12- to 39-years-old should consider waiting eight weeks between the first and second dose of the Pfizer or Moderna vaccines to reduce the risk of myocarditis. Canadian public health authorities had found that the rate of myocarditis after Pfizer or Moderna vaccination was higher when the time between the first and second dose was fewer than 30 days.

Moderna’s second dose appears associated with a higher risk of myocarditis than Pfizer’s, according to data presented to the CDC’s committee of vaccine experts in February. Public health authorities in Ontario, Canada have found that the rate of myocarditis was 5 times higher for males ages 18-24 following a second dose of Moderna compared to Pfizer.

However, the overwhelming majority of people who developed myocarditis after vaccination recovered fully and most of them did not report any effect on their quality of life, according to a CDC survey of health-care providers presented at the February meeting.