(Reuters) - Both commercially available mRNA vaccines are safe, with low risks of major adverse events, according to a large study that tracked 433,672 U.S. veterans for 38 weeks following vaccination.
Half the group had received Moderna's COVID vaccine and the other half with similar characteristics and risk factors had received Pfizer/BioNTech shots.
"Small-magnitude differences between the two vaccines were seen within 42 days of the first dose," researchers reported in JAMA Internal Medicine.
"Individuals receiving the Moderna vaccine were slightly less likely - a difference of less than two-tenths of one percent - to experience stroke, myocardial infarction, other thromboembolic events, or kidney injury," said coauthor Dr. Arin Madenci of Harvard T.H. Chan School of Public Health.
For example, among every 10,000 study subjects, there were roughly 11 more strokes and 11 more heart attacks over the ensuing months in Pfizer/BioNTech recipients than in Moderna recipients.
The study did not establish a causal link between the vaccines and heart attacks, strokes and the other major adverse events. One possibility, Madenci said, is that the differences his team observed "may be explained by a lower effectiveness of the Pfizer vaccine in preventing COVID-19" and the resulting after-effects in patients who developed the disease.
SOURCE: https://bit.ly/3xN4L7g JAMA Internal Medicine, online June 13, 2022.
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