Vaccination against swine flu caused narcolepsy in several European countries

Narcolepsy is a rare sleeping disorder that gives sleep onset rapid eye movement periods and excessive daytime sleepiness. It is divided into two subgroups, narcolepsy type 1 where there also is orexin deficiency and cataplexy and narcolepsy type 2 that lack these features. Narcolepsy type 1 is assumed to be an autoimmune disease with destruction of orexin-producing cells. The pathology behind is unclear. There is a strong association to a class II HLA allele, HLADQB1*06:02 and the H1N1-virus and streptococcal infections has also been associated with narcolepsy. The severity of narcolepsy differs between patients from those who can manage their disease without medication to those who has a severe impact on their everyday life. There is a diagnostic delay between the onset of symptoms and time for diagnosis that in some cases can be more than a decade. The global mean prevalence is 30 per 100 000 inhabitants. The incidence in children in northern Europe has risen since 2010. An early study of the 2009 H1N1 influenza A pandemic indicated a high mortality and prompted efforts to rapidly come up with a vaccine. One of these was Pandemrix that was the most widely used in Europe and 61 % of the inhabitants in Sweden was vaccinated. Studies have shown an increased incidence of narcolepsy type 1 in European countries that had used Pandemrix, but no increased risk was seen in countries that had used other vaccines than Pandemrix.