As fewer children get their flu shots, cases of a rare, severe complication are rising. Last season, the U.S. experienced the highest number of pediatric flu deaths in 15 years.

Cases of pediatric ANE and other flu-related encephalopathies are on the rise. During the 2024-25 flu season, 109 children were diagnosed with the rare complication, according to new data from the Centers for Disease Control and Prevention.

According to the new report, 84% of kids with influenza-associated encephalopathy whose vaccination status was known weren’t vaccinated.

The finding comes as the nation logged 280 pediatric flu deaths last year, the deadliest ever aside from the 2009-10 H1N1 pandemic, as well as falling rates of children vaccinated against influenza.