The CHMP reviewed all available data, including new findings from Sweden and France on the suspected link between narcolepsy in children and adolescents and Pandemrix. The CHMP concluded that, following the earlier results of an epidemiological study from Finland, the new evidence strengthened the signal in children and adolescents, but that the data had methodological limitations. The relationship between Pandemrix and narcolepsy is still under investigation.
Preliminary results of the Swedish registry study from October 2009 to December 2010 on Pandemrix vaccination and the risk of narcolepsy indicates a four-fold increase of cases of narcolepsy in children and adolescents (below 20 years of age) who received Pandemrix compared with unvaccinated people of the same age. The additional risk corresponds to an additional 3-4 narcolepsy cases per 100,000 vaccinated subjects. These results are broadly in line with the study results from Finland indicating an association between Pandemrix and narcolepsy in children and adolescents. The study did not identify any increased risk in adults. The CHMP concluded that the study was well conducted, although it has inherent limitations.
An analysis of narcolepsy reports in France provides some further evidence.
The lack of a clear increase in reports of narcolepsy following Pandemrix in other European Union (EU) and non-EU countries may point towards the influence of other unknown factors affecting the trend seen in some countries. Also, there is currently no clearly identified biological plausibility for an association between Pandemrix and narcolepsy, and further non-clinical studies, especially in the juvenile setting, are needed.
The CHMP considers it important to gather more data on the use of Pandemrix and related vaccines in a variety of countries to further assess this concern. A variety of research efforts are now ongoing. These include an epidemiological study of narcolepsy and pandemic vaccines conducted by the European Centre for Disease Prevention and Control (ECDC) through a network of research and public health institutions (VAESCO) in nine EU Member States, and an epidemiological study conducted by GlaxoSmithKline (the marketing authorisation holder of Pandemrix) in Canada. Preliminary results of the VAESCO study and of the Canadian study are expected by July 2011.
The CHMP is working with experts from across the EU to assess the possible safety concern and any impact on the benefit-risk balance of Pandemrix. The CHMP plans to hold an expert meeting with participation of international experts, the World Health Organization (WHO) and ECDC.
The European Medicines Agency will provide updates as new information becomes available.