LONDON (Reuters Health) Jul 21 - European regulators have recommended restricting the use of GlaxoSmithKline's pandemic flu vaccine Pandemrix because of a potential risk of narcolepsy in children or adolescents.
The European Medicines Agency said on Thursday that Pandemrix should only be used in people under 20 years in the absence of seasonal trivalent influenza vaccines, following its link to very rare cases of narcolepsy in young people.
Overall, the vaccine's benefit-risk balance remains positive, the watchdog added.
More than 31 million doses of Pandemrix have been given to people in 47 countries, and GSK said it had been notified of 335 cases of narcolepsy in those vaccinated as of July 6. Two-thirds of the narcolepsy cases were in Finland and Sweden.
Britain's biggest drugmaker said in a statement it had committed to conduct further research into any potential association between Pandemrix and narcolepsy.
Pandemrix was widely used during the 2009-10 outbreak of H1N1 swine flu, although it was not administered in the United States.
Several other drugmakers, including Novartis , Sanofi , CSL and Baxter also made vaccines against H1N1 flu during the pandemic, which was declared over in August last year.
Finnish and Swedish researchers were the first to raise concerns over a possible narcolepsy link to Pandemrix last August after noting cases in children recently given the GSK shot.
One research team earlier this year suggested children given Pandemrix were nine times more likely to suffer from the condition.
Researchers at Finland's National Institute for Health and Welfare said the increase they found in narcolepsy was "most likely" a joint effect of Pandemrix and some other factor or factors.