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).