Purpose of review: A number of European countries have reported a dramatic increase in the rates of childhood narcolepsy with cataplexy in children immunized with a split-virion adjuvanted swine flu vaccine. Here, we review the strengths and weaknesses of these epidemiological studies and possible neuroimmunological mechanisms.
Recent findings: Initial concerns of a 13-fold increased relative risk of narcolepsy were raised by the Scandinavian health protection agencies in 2010. Subsequent retrospective studies support these findings in Canada, France, Ireland, England and Denmark. The cases are predominantly young children who present with severe and rapid onset of cataplexy as well as narcolepsy often within a few weeks of vaccination. The proposed mechanism for postvaccination narcolepsy is one in which an environmental trigger causes or enhances an antibody-mediated autoimmune response in patients with a preexisting genetic susceptibility. However, there have not yet been any reports of specific autoimmunity, either antibody or T-cell-mediated.
Summary: There is a strong association between narcolepsy and H1N1 vaccination. However, whether this reflects a true increase in affected individuals or a hastening of disease onset in individuals who would otherwise have developed narcolepsy later will become clear in the coming years. The pathological explanation of this association and narcolepsy is likely to be autoimmune, although supportive evidence is lacking.Video abstract available: See the Video Supplementary Digital Content 1 (http://links.lww.com/COPM/A9).