(HealthDay News) — The incidence of selected serious outcomes is not significantly higher at 1 to 21 vs 22 to 42 days postvaccination with mRNA COVID-19 vaccines, according to a study published online in the Journal of the American Medical Association.

Nicola P. Klein, MD, PhD, from Kaiser Permanente Northern California in Oakland, and colleagues conducted an interim analysis of safety surveillance data from the Vaccine Safety Datalink to monitor 23 serious outcomes. The incidence of events that occurred among vaccine recipients 1 to 21 days after either dose of mRNA vaccine was compared to that of vaccinated comparators who had received their dose 22 to 42 days earlier. A total of 11,845,128 doses of mRNA vaccines (57% BNT162b2) were administered to 6.2 million individuals.

The researchers found that the incidence of events per 1 million person-years during the risk versus comparison intervals was 1612 vs 1781 for ischemic stroke; 1179 vs 1345 for appendicitis; and 935 vs 1030 for acute myocardial infarction (rate ratios [95% confidence intervals], 0.97 [0.87 to 1.08]; 0.82 [0.73 to 0.93]; and 1.02 [0.89 to 1.18], respectively). None of the outcome associations met the prespecified requirement for a signal. The incidence of confirmed anaphylaxis was 4.8 and 5.1 per million doses of BNT162b2 and mRNA-1273, respectively.

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“It is our top priority to do the science and communicate quickly and clearly with health care providers and the public, as COVID-19 vaccines continue to undergo the most intensive safety monitoring in US history,” a coauthor said in a statement.

Several authors disclosed financial ties to the pharmaceutical industry.

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