This initiative was taken following the indication of a potential association between the 2009 pandemic influenza A(H1N1) monvalent vaccine and the occurrence of narcolepsy following reports, especially in children from Finland and Sweden.

In February 2011, ECDC published a report concerning a rise in narcolepsy in children and adolescents in some northern countries.

A four-fold increased incidence of narcolepsy in vaccinated children/adolescents compared to unvaccinated children was observed in this register-based cohort study.

In late March, 2011 ECDC reported that the Swedish Medical Product Agency published preliminary results from an on-going cohort study involving 5.3 million people, where 67% of children and adolescents and 51.0% of adults were vaccinated with Pandemrix.

The European Medicines Agency (EMA) was key in the Europe during the 2009 pandemic concerning the authorisation and the benefit – risk assessment of the novel pandemic vaccines.

ECDC has previously summarised information concerning the appearance of narcolepsy following the use of a specific pandemic vaccine (Pandemrix®) in children and adolescents in three European Countries.

EMA recommends restricting use in persons under 20 years of age Pandemrix to be used only in the absence of seasonal trivalent influenza vaccines, following link to very rare cases of narcolepsy in young people. Overall benefit-risk remains positive.

​A pair of linked papers from Finland concerning the above topic, one epidemiological and the second combining both clinical and epidemiological were published on March 28th in the open access journal, PLoS One.(1,2).