Same-day COVID, flu shots show no added adverse event risk

Clinical takeaway: Clinicians can coadminister COVID and flu vaccines without expecting more adverse events, even in older patients.

Most COVID-19 vaccine safety data come from early shots studied on their own. Whether that reassuring information extends to today's updated formulations, given alongside a flu shot at a single visit, hasn't been thoroughly tested. Researchers used Veterans Affairs records from 2022 through 2025 to compare same-day coadministration against flu vaccination alone.

Pairing the two shots at a single visit simplifies the schedule and supports uptake, which still matters: COVID-19 caused an estimated 879,000 hospitalizations and 101,000 deaths in the U.S. across the 2023-2024 season. Yet the prior safety evidence for that pairing, under current formulations, has come from studies tracking few outcomes over short windows.

Across all three adverse event severity tiers, from life-threatening events to self-limiting, 90-day risk was indistinguishable between groups with coadministered shots. Of 46 potential outcomes, only two reached significance, in opposite directions: syncope edged up, tinnitus edged down. Both fell in the least severe tier, and neither held up once the authors accounted for testing 46 outcomes at once. The pattern was the same across all three vaccine formulations.

Using VA records from September 2022 through August 2025, the target trial emulation compared about 705,000 adults who got both shots at one visit with 1.8 million who received flu vaccine alone, tracking 46 prespecified adverse events over 90 days. The design compared two vaccinated groups rather than vaccinated against unvaccinated, avoiding the healthy-vaccinee bias common to earlier work.

The result simplifies a common conversation: patients hesitant to get both shots at once have little safety reason to space them out. But the older, mostly male VA cohort means small risks in younger people can't be ruled out, including the myocarditis signal tied to the early COVID-19 shots in young men.

Source: Xie Y, et al. (2026 Jun 30) Ann Intern Med. Adverse events after same-day COVID-19 and influenza vaccination versus influenza vaccination alone: a target trial emulation