WEDNESDAY, June 3, 2026 (HealthDay News) — For children ages 2 to 5, those with fall birthdays are more likely to be vaccinated and less likely to be diagnosed with the flu, according to a research letter published online June 1. JAMA Pediatrics.
Christopher M. Worsham, MD, MPH, of Massachusetts General Hospital in Boston, and colleagues examined the effectiveness of influenza vaccination during individual influenza seasons from 2016 to 2023 among children aged 2 to 5 years and fall versus summer births.
Children with fall birthdays were more likely to be vaccinated and less likely to get the flu in each flu season examined, the researchers found. Depending on the season, influenza vaccination rates were 8.6 to 12.5 percentage points higher for fall children compared to summer births, and flu diagnosis rates were 1.0 to 1.4 percentage points lower. No difference was observed in the rate of diagnosis of false cases of viral infection. For every 100 children who were vaccinated by their birthday, there were 9 to 14 fewer cases of influenza, depending on the season.
Senior author Anupam B. “For everything we want to know and understand, a randomized controlled trial is impossible,” Jena, MD, Ph.D., of Harvard Medical School in Boston, said in a statement. “But we have an incredible amount of data out there, and there are random experiments sitting in that data, waiting to be discovered.”
One author has revealed links to health care; two authors revealed their connections to the publishing and media industries.
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