Same-Day COVID and Flu Shots Pose No Extra Risk, Large Study Confirms

For health-conscious adults juggling annual vaccine schedules, a new large-scale study offers clear practical guidance: getting your COVID and flu shots on the same day is just as safe as getting the flu shot alone. Published in the Annals of Internal Medicine, the research analyzed electronic health records from the VA, covering more than 2.5 million people across three recent COVID vaccine formulation eras between September 2022 and August 2025.

The study used a target trial emulation design, comparing 705,124 people who received both vaccines on the same day against 1,813,205 who received only a flu shot. Importantly, the active-comparator design — matching two vaccinated groups rather than comparing vaccinated to unvaccinated — helped reduce healthy-vaccinee bias, strengthening the validity of the findings.

Researchers assessed 46 individual adverse events across three composite outcome categories: serious or life-threatening, clinically significant, and less severe or self-limiting. None reached statistical significance after correcting for multiple comparisons. Two outcomes showed nominal signals — a slight increase in syncope risk and a slight decrease in tinnitus risk — but neither held up under rigorous statistical correction. Myocarditis risks were small in both groups.

The study's timeframe is a key strength. Most widely cited vaccine safety data still derive from early pandemic vaccines administered to immunologically naive populations. This research reflects contemporary hybrid immunity — people who have had multiple vaccine doses and likely prior infection — offering more relevant safety reassurance for today's public.

Lead researcher Ziyad Al-Aly emphasized that despite declining COVID severity, the disease remains a real threat, especially for older adults and those with comorbidities. The risk-benefit balance still favors vaccination. Practically, coadministration saves time and may improve adherence to both vaccine recommendations, making it a sensible default for most adults.