Knowledge Affirm Pfizer, Moderna Vaccines Convey Small Threat of Myocarditis for Boys

Newly released data confirm that the Pfizer-BioNTech and Moderna vaccines are both associated with rare heart problems and that this side effect is most common in adolescent boys and young men after the second vaccination. Still, the benefits of vaccination continue to outweigh the risks, scientists said.

The side effects are usually mild, temporary, and infrequent. For every million doses of the second vaccination given to 12- to 39-year-olds, there were 14 to 20 additional cases of heart problems the centers for the new data presented Monday at a meeting of an independent advisory committee for the city Disease control and prevention.

“The data suggest a link between myocarditis and mRNA vaccination in adolescents and young adults,” said Dr. Grace Lee, Stanford Pediatrician and Chair of the Committee, at Monday’s meeting. “More data is gathered to understand potential risk factors, optimal management strategies and long-term results.”

But the benefits of vaccines are considerable, even for those in the highest risk groups. According to an analysis submitted Monday by a CDC scientist, every million doses of the Pfizer vaccine given to 16- and 17-year-old boys is expected to cause 73 cases of heart problems, along with more than 56,000 Covid -19 prevents cases and 500 associated hospital admissions.

The meeting takes place while federal regulators grapple with the risk-benefit calculations of vaccinating young Americans. In recent weeks, regulators have been particularly concerned about the risks of two heart diseases: myocarditis, which is inflammation of the heart muscle, and pericarditis, which is inflammation of the membrane that surrounds the heart.

The new data comes from two federal safety monitoring systems: the Vaccine Adverse Event Reporting System (VAERS), which collects unaudited self-reports, and the Vaccine Safety Datalink, which contains vaccine and health records from nine health organizations.

As of August 18, VAERS had received more than 2,500 reports of heart problems in newly vaccinated individuals. Overall, the risks appear to be increased for males between the ages of 12 and 49 and females between the ages of 12 and 29, according to the data.

Reports were far more common after the second dose than after the first, and more common in men than women. For example, for every million doses of the second Pfizer shot, 71.5 reported cases of myocarditis were reported in 16- and 17-year-old boys, compared with just 8.1 in girls of the same age.

The results agreed with data from the Vaccine Safety Datalink. Using this system, the researchers confirmed 56 cases of heart problems in 12- to 39-year-olds who had received an mRNA vaccine within the last three weeks. The majority were male.

For every million doses given to 12 to 39 year olds, there were 14.4 cases of heart problems after the second Pfizer injection. In 18- to 39-year-olds, there were 19.7 additional cases after the second Moderna shot, which was not yet approved for children, the scientists calculated.

Most of the patients were hospitalized for the disease but recovered quickly; 76 percent were released within two days. No deaths were reported.

The scientists also highlighted a study published last week in the New England Journal of Medicine that found that the risk of myocarditis was significantly higher after infection with the virus than after vaccination. “The incidence and hospitalization rates of Covid-19 are increasing rapidly,” said Dr. Hannah Rosenblum, a CDC scientist, at the meeting.

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