Flu vaccination rates this year are on par with 2024 among adults, but have dipped in childrenTess Crowley/Chicago Tribune/Getty ImagesWhile the US declared its intention to leave the World Health Organization (WHO) on 20 January, the process of severing ties with the international public health body formally takes one year. Yet US health agencies have already retreated from nearly all coordinated global health efforts around influenza surveillance. The move could jeopardise the efficacy of the next batch of flu vaccines both for the US and the rest of the world.