Why next year's flu shot might not be as good as it should be

In a typical year, several thousand samples from flu patients around the world arrive at the U.S. Centers for Disease Control and Prevention. They're crucial for understanding the virus's evolution and help form the bedrock of the World Health Organization's effort to design the next annual flu shot.

But this year, the flow of that data has come "pretty much to a grinding halt," says Demetre Daskalakis, who led the National Center for Immunization and Respiratory Diseases at CDC until he resigned in August.

From February through July, he says CDC received only 427 samples, 60% fewer than the same time period last year. Only 12 countries had sent CDC samples by then, down 65% compared with 2024. CDC did not respond to NPR's request for comment.

"When those viruses are not coming in,