Using a population-based prospective cohort study, the team analyzed data from regional vaccination registries and national health registries, covering seven healthcare regions and 61% of the Swedish population.

While the team did not identify any link to a large number of immune-related or neurological diseases, they did confirm an increased risk in diagnosis of narcolepsy in individuals younger than 20 years of age, and observed a trend towards an increased risk amongst young adults between 21 and 30.

"The follow-up of Pandemrix vaccinations in a large registry based study in Sweden confirms an increased risk of narcolepsy in children and adolescents, while also providing reassuring results for a large number of other neurological and immune related diseases," said Dr. I. Persson from the Karolinska Institutet, Stockholm.

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Journal Reference:

1. I. Persson, F. Granath, J. Askling, J. F. Ludvigsson, T. Olsson, N. Feltelius. Risks of neurological and immune-related diseases, including narcolepsy, after vaccination with Pandemrix: a population- and registry-based cohort study with over 2 years of follow-up. Journal of Internal Medicine, January 2014