In spring last year, the number of narcolepsy cases in Beijing, China, multiplied threefold. Now, it looks like the swine flu pandemic of the previous winter was to blame. Previously, similar rises in cases of narcolepsy – a disorder that causes sleepiness at inappropriate times – have been linked to use of a swine flu vaccine. The cause was presumed to lie in the drug’s adjuvants – additives that boost the immune response to the vaccine. The claim puzzled researchers who saw a concurrent rise in narcolepsy cases in China, where few people had opted to get vaccinated and those who did received a vaccine without adjuvants. Could the flu itself be to blame?
