(CNN) — Cases of inflammation of the heart after vaccination with covid-19 mRNA are rare and occur more frequently in young men, suggests research published this Monday in the journal JAMA Internal Medicine.
Myocarditis is a type of inflammation of the heart.
Rare cases of the disease have been associated with covid-19 mRNA vaccines, especially among young men, and information about the risk is now included in vaccine materials.
A group of Kaiser Permanente physicians analyzed 2,392,924 adults receiving care at Kaiser Permanente Southern California, who received at least one dose of the Pfizer or Moderna vaccine against covid-19 between December 14, 2020 and December 20. July 2021. About 54% of those studied were women; 35.7% were under 40 years of age.
Among those who received the vaccines, there were 15 cases of myocarditis, all in men between the ages of 20 and 32. Two of those cases occurred after the first dose and 13 after the second. This represents a rate of approximately 0.8 cases per million first doses and 5.8 cases per million second doses.
The team found that none of the patients who developed myocarditis after vaccination had prior heart disease. About 93% developed chest pain within 5 days of vaccination. None of the patients required the intensive care unit and their symptoms resolved with “conservative treatment”.
The team says that although myocarditis after vaccination with mRNA vaccines is rare, the increased rate among young men warrants further research.
They also analyzed 1,577,741 people who did not receive the vaccines, of which 49.1% were women and 53.7% were under 40 years of age. In this group, there were 75 cases of myocarditis, 52% of which corresponded to men between 32 and 59 years of age.
Vaccines, a safe method, despite possible myocarditis
In a related editorial published in JAMA Internal Medicine, doctors from the University of California, San Francisco and NYC Health + Hospitals stated that the rare cases of myocarditis after vaccination do not change the fact that covid-19 vaccines are a method. safe and effective to prevent infection.
“Overall, vaccination-related myocarditis was a rare and mostly mild adverse event,” wrote Drs. Vinay Guduguntla and Mitchell Katz.
And the risk is not unique to covid-19 vaccines, they say. “Furthermore, this risk is small when compared to the morbidity and mortality of covid-19 infection, in which up to 28% of hospitalized patients showed signs of myocardial injury,” they wrote.
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