An H1N1 flu vaccination campaign was organized between October 2009 and March 2010 in several countries, particularly in northen Europe. In close connection with this vaccination (Pandemrix), new childhood narcolepsy cases with abrupt symptom onset appeared in many European countries.
The experience from Pandemrix vaccination contributed to better recognition and earlier diagnosis of childhood narcolepsy and facilitated understanding of the autoimmune mechanisms of the disease.