Sanita Masoudi, Daniela Ploen and Eberhard Hildt
After the mass-vaccination campaign during the influenza A (H1N1) 2009 pandemic, a significant increase in narcolepsy incidence was observed initially in Scandinavia, later in other European countries and recently also in Canada. Narcolepsy is a sleep disease caused by the loss of hypocretin-producing cells in the hypothalamus. Almost all narcolepsy patients carry the HLA-DQB1*0602 allele, giving a link to an autoimmune-mediated process. Most of the observed narcolepsy cases were correlated to the vaccination with Pandemrix, the most frequently used vaccine in the EU, and a slight connection to Arepanrix was also detected, which was distributed in Canada. Both vaccines were adjuvanted with AS03, suggesting a possible link between AS03 and narcolepsy. No narcolepsy cases were detected with MF59-adjuvanted or non-adjuvanted influenza vaccines. Recent studies reported differences between Pandemrix and Arepanrix and suggested the vaccine rather than the adjuvant as a suspect for narcolepsy development following vaccination. In addition, in China an increase of narcolepsy cases was reported to occur in absence of vaccination. Possible factors and potential additive effects that may have triggered narcolepsy after the pandemic vaccination are being reviewed in this paper.