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HELSINKI/LONDON, May 23 (Reuters) - GlaxoSmithKline Plc's H1N1 pandemic flu shot may put adults at higher risk ofdeveloping narcolepsy, not only children as previous studiesfound, Finland's National Institute for Health and Welfare saidon Thursday.
Growing evidence of a link between GSK's Pandemrix vaccineand an increase in narcolepsy, a rare sleep disorder, amongchildren who received it in Europe has delayed approval of asimilar vaccine in the United States.
Data published this year in the British Medical Journalfound that children in England who had been vaccinated withPandemrix during the 2009-10 H1N1 swine flu pandemic had a14-fold higher risk of developing narcolepsy, equating to aboutone in 50,000.
Finland's National Institute said an analysis of hospitaland primary care data in Finland found that people aged between20 and 64 who had been vaccinated with Pandemrix were 3 to 5times more likely to develop narcolepsy than unvaccinatedpeople.
Narcolepsy is a lifelong, incurable and potentiallydebilitating sleep disorder that can cause hallucinations, bouts of daytime sleepiness and cataplexies - where strongemotions trigger a sudden loss of all muscle strength.
Previous studies in Finland, Sweden and Ireland have alsofound a link between Pandemrix and narcolepsy, and GSK says morethan 800 cases linked to the shot have been reported in Europe.
The British drugmaker says some 30 million doses of thevaccine were administered across Europe during the 2009-10 H1N1pandemic. The pandemic was declared over in August 2010.
The company acknowledges an association but says there is asyet insufficient evidence to show that Pandemrix is the cause.
