HMN 2026: How Same day administration of COVID-19 and influenza vaccines are not associated with increase in adverse events

A target trial emulation found that same-day coadministration of the COVID-19 and influenza vaccines was not associated with a higher risk of serious or clinically meaningful adverse events compared with receiving only an influenza vaccine. Across multiple updated COVID-19 vaccine versions, overall safety outcomes were similar.

The findings suggest receiving both vaccines at the same visit is safe. The study is published in Annals of Internal Medicine.

Researchers from Washington University in St. Louis conducted a target trial emulation using data from 2.5 million patients in the U.S. Department of Veterans Affairs health care system between Sept. 1, 2022, and Aug. 26, 2025, to evaluate the 90-day risks for adverse events after coadministration of COVID-19 and influenza vaccines across the bivalent, XBB-adapted and KP-adapted COVID-19 vaccination periods.

They compared more than 700,000 people who received both vaccines with more than 1.8 million who received only the influenza vaccine and examined 46 potential adverse events, grouped by severity.

The results showed that same-day vaccination with the COVID-19 and influenza vaccines did not increase the risk for cardiovascular and thrombotic events, neurological disorders, immune-mediated disorders and other outcomes during three updated COVID-19 vaccine formulation periods.

The findings support the short-term safety of coadministration in adults and may help inform ongoing vaccine policy discussions.

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