Increased risk of narcolepsy observed among children and adolescents vaccinated with PandemrixR
1 Feb 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
In 2009, among countries using similar pandemic vaccine as was used in Finland, an increase in cases of narcolepsy has been observed only in Finland, Sweden and Iceland. Contrary to the observations in Finland, narcolepsy has occurred in greater numbers than expected also among unvaccinated children and teenagers in Iceland.
The association between narcolepsy and PandemrixR vaccine requires more investigations
During the coming months, these preliminary register based results will be confirmed in Finland. In further investigations, special attention will be given to infections and other stimuli in close time association with the pandemic vaccination. The significance of the possible joint effects will be explored.
In addition, other significant co-factors contributing to the onset of narcolepsy will be evaluated in epidemiologic, immunologic and genetic studies planned. The main aim of the immunologic studies is to clarify, whether the immunological responses to the different components of the Pandemrix® vaccine and to the A(H1N1) virus among those children and teenagers with genetic disposition to narcolepsy and those fallen ill with narcolepsy differ from the immunological responses of other children and teenagers not belonging to these risk groups.
It is also of utmost importance to find out whether the association is observed also elsewhere than in Finland. At present, Finland is participating in the ECDC contracted, VAESO led narcolepsy background incidence and case control studies which are being conducted in 9 European Union countries by pharmacovigilance researchers from Public Health Institutes, Regulatory Agencies and Universities. These studies will evaluate the contribution of the pandemic vaccines and other risk factors in the onset of narcolepsy, and confirm whether increase in incidence in narcolepsy is seen in other countries. The outcomes of these studies will be reported during early summer 2011.
By January 24, 2011, 56 notifications of narcolepsy in association with Pandemrix® vaccination have been received by the National Vaccine Adverse Events Register maintained at the National Institute of Health and Welfare in Finland. Of these, 54 cases belonged to the age group of 4-19 years. Among most of the notified cases, the onset of symptoms of narcolepsy had started approximately two months following Pandemrix® vaccination.
The final report from the National Narcolepsy Task Force will be released by 31st August 2011.
WHO: Pandemrix® vaccine and increased risk of narcolepsy
Director of Department of Vaccines and Immune Protection, Chairman of the Task Force
National Institute of Health and Welfare, THL
tel +358 20 610 8678
Vaccine Safety Officer, Secretary of the Task Force
National Institute of Health and Welfare,THL
Tel +358 20 610 8246