The 2009 H1N1 influenza pandemic left a troubling legacy in Europe: More than 1300 people who received a vaccine to prevent the flu developed narcolepsy, an incurable, debilitating condition that causes overpowering daytime sleepiness, sometimes accompanied by a sudden muscle weakness in response to strong emotions such as laughter or anger. The manufacturer, GlaxoSmithKline (GSK), has acknowledged the link, and some patients and their families have already been awarded cpmpensation. But how the vaccine might have triggered the condition has been unclear.In a paper in Science Translational Medicine (STM) this week, researchers offer a possible explanation. They show that the...