Public Health

Though rare, Moderna Covid vaccine recipients are at higher risk of heart inflammation than Pfizer

Moderna’s two-dose Covid-19 vaccine is associated with a higher risk of heart inflammation than Pfizer’s, but the benefits of both companies’ shots outweigh the risks, according to a panel of outside experts from the Centers for Disease Control and Prevention.

The CDC’s Advisory Committee on Immunization Practices met Friday to discuss the risks of developing myocarditis after receiving either Moderna or Pfizer vaccines.

Myocarditis is inflammation of the heart muscle that can lead to serious health problems, according to the National Heart, Lung and Blood Institute. Although myocarditis most commonly occurs after viral infection, the CDC has found an association between heart inflammation and vaccination using Moderna and Pfizer shots.

The risk of myocarditis after a Covid vaccination is highest in teenage boys and young men after the second dose of mRNA vaccines, the technology used by both Moderna and Pfizer. Symptoms develop within a few days after vaccination, including chest pain, shortness of breath, palpitations, and fatigue.

Although rare, the Pfizer and Moderna vaccines have been linked to a risk of myocarditis. But the risk was higher after the second dose of Moderna’s vaccine in people ages 18 to 39, according to the CDC’s safety surveillance program, which collects data from nine health organizations in eight states.

For every 1 million second doses administered, Moderna vaccine recipients had 10.7 additional cases of myocarditis and pericarditis compared to people who received Pfizer, according to the study. The difference was even greater in men, who had 21.9 extra cases of myocarditis and pericarditis with the second Moderna vaccine, while women had 1.6 extra cases.

However, there was no difference in the symptoms experienced by people who received the vaccines from either company. According to the study, most patients were only in the hospital for one day and nobody was admitted to the intensive care unit.

Health officials in Ontario, Canada found that the rate of myocarditis in men aged 18 to 24 was five times higher than Pfizer’s after the second dose of Moderna’s vaccine. The rate of myocarditis was also higher in people of the same age group who received Pfizer as the first dose and Moderna as the second dose than in people who received two Pfizer shots.

dr Sara Oliver, a CDC official, said more myocarditis cases could be expected after Moderna’s vaccine, but the company’s vaccines would also prevent more Covid hospitalizations than Pfizer’s vaccine. “The benefits of the mRNA vaccines still far outweigh the potential risk,” Oliver said.

Canada, the United Kingdom and several other countries have recommended Pfizer’s vaccine over Moderna’s vaccine in higher-risk age groups. dr Pablo Sanchez, a professor of pediatrics at Ohio State University, said CDC vaccine experts should consider a similar recommendation.

“It may be that, at least in the highest-risk groups, younger males, we should recommend preferring Pfizer to Moderna,” Sanchez told the committee.

Researchers are still studying what triggers myocarditis after a Covid vaccination. Canadian health officials also found that the rate of myocarditis was higher for both Moderna and Pfizer’s vaccines when the interval between the first and second doses was less than 30 days.

CDC vaccine experts are considering a longer interval of 8 weeks between the first and second doses of both companies’ vaccines to address the risk of myocarditis. Moderna’s vaccine is fully licensed for adults 18 years and older. Pfizer’s vaccine is fully licensed for people ages 16 and older and is licensed for children ages 5 to 15 on an emergency basis.

The overwhelming majority of people who had myocarditis after the Covid vaccination made a full recovery and most reported no impact on their quality of life, according to a CDC survey of cardiologists and other health care providers.

The survey found that 81% of their patients who developed myocarditis after vaccination made a full or likely recovery within 37 weeks of their diagnosis. Another 15% had improved while 1% had not improved.

Most patients, 83%, had limitations in their physical activity after their myocarditis diagnosis. However, 39% still had limitations at the time of the survey. Doctors recommend that people who develop myocarditis avoid vigorous physical activity for a few months to ensure their heart fully recovers.

According to the data, there were no known post-vaccination myocarditis deaths in the group.

People are at much higher risk of developing myocarditis from Covid infection than the vaccines, according to the Department of Health and Social Care. The risk of myocarditis from Covid is 100 times greater than developing the disease after a Covid vaccination, according to a recent article published in Nature Reviews Cardiology.

“It’s a bit dangerous to focus on vaccines and myocarditis when the elephant in the room is really a real disease, a real infection from COVID-19 and the potentially devastating, even life-threatening, myocarditis,” said Dr. Camille Kotton, an expert on infectious disease and people with compromised immune systems at Massachusetts General Hospital in Boston.

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