This report summarises the results from two epidemiological studies to investigate a possible association between an unexpected increase in narcolepsy cases following the use of the influenza A(H1N1)pdm09 vaccines. The studies were conducted by the Vaccine Adverse Event Surveillance and Communication (VAESCO) Consortium under the auspices of ECDC and undertaken in Denmark, Finland, France, Italy, the Netherlands, Norway, Sweden and the United Kingdom. This Technical Report In Brief accompanies the full Report ‘Narcolepsy in association with pandemic influenza vaccination- A multi-country European epidemiological investigation’.

This report summarises the results from two epidemiological studies conducted by the Vaccine Adverse Event Surveillance and Communication (VAESCO) Consortium undertaken in eight European Union (EU)/European Economic Area (EEA) countries in order to investigate a possible association between an unexpected increase in narcolepsy cases following the use of influenza A(H1N1)pdm09 vaccines. Narcolepsy is an underdiagnosed disease of widely unknown etiology.