By Jonathan Lambert A shot for a flu vaccination. A late February meeting of scientists from around the world is figuring out the recipe for the best vaccine for the upcoming fall flu season. Jens Kalaene/picture alliance/via Getty Images hide caption For the past week, about 50 flu scientists from around the world have been cramming into a conference room at a Hilton hotel in Istanbul, Turkey. Their goal is to design a flu shot that will confer the best protection for the next flu season —starting in the fall of 2026. Each day, they pore over reams of data — about how the virus is evolving worldwide, how well last year's shot performed, and which strains might be easiest to mass produce for a vaccine. The meeting, convened by the World Health Organization twice a year, is a critical moment for the WHO's Global Influenza Surveillance and Response System. It's also "really tedious," says Dr.…