Posted February 2, 2011
Among those 4-19 years of age who received Pandemrix®-vaccine had a manifold increased risk of falling ill with narcolepsy during the 8 months following vaccination in comparison to those unvaccinated in the same age group. Based on the evaluation done so far, the National Narcolepsy Task Force finds it probable that Pandemrix®-vaccination contributed to the observed increase in incidence of narcolepsy among those 4 -19 years of age. Currently, the most likely explanation is that the increase in narcolepsy is by joint effect of the vaccine and some other factor(s). At the moment, there is no evidence that the increase in narcolepsy observed in Finland could be attributed to the vaccine lots used. The results can be read in the Interim Report of the Task Force which is published on February 1st, 2011.
The association of Pandemrix-vaccination and narcolepsy was studied using extensive registry based data. Data gathered from hospital discharge registries on patients fallen ill with narcolepsy during years 2009-10 was linked with data from primary care records on pandemic vaccination. The observed association is so evident that it is unlikely that other so-called confounding factors could fully explain the phenomenon.
In Finland during years 2009-10, 60 children and adolescents aged 4-19 years fell ill with narcolepsy. These figures base on data from hospitals and primary care, and the review of individual patient records by a panel of neurologists and sleep researchers. Of those fallen ill, 52 (almost 90 percent) had received Pandemrix® vaccine, while the vaccine coverage in the entire age group was 70 percent. Based on the preliminary analyses, the risk of falling ill with narcolepsy among those vaccinated in the 4-19 years age group was 9-fold in comparison to those unvaccinated in the same age group. This increase was most pronounced among those 5-15 years of age. No cases were observed among those under 4 years of age. Also, no increase in cases of narcolepsy or signs of vaccination impacting risk of falling ill with narcolepsy was observed among those above 19 years of age.
In addition to Finland, increase in cases of narcolepsy observed only in Sweden and Iceland.