(Corrects spelling of author's name in by-line)
* European drug regulators investigating vaccine's safety
* Regulators say benefit-risk balance remains positive
* GlaxoSmithKline says too early to draw conclusions
HELSINKI/LONDON, Feb 1 (Reuters) - Finland's national health institute said on Tuesday preliminary research suggested children who got GlaxoSmithKline's (GSK.L) Pandemrix vaccine against H1N1 pandemic flu were nine times more likely to suffer from a sleeping disorder called narcolepsy.
The research, which the institute said had yet to be confirmed, found an increase in cases of narcolepsy among children aged four to 19 years who had the vaccine.
Researchers at the National Institute for Health and Welfare (NIHW) said it was "most likely" the increase in narcolepsy was a joint effect of Pandemrix and some other factor or factors.
GSK said it was aware of the investigation, which was conducted by the Finnish national narcolepsy committee and published by the NIHW, but said it was too soon to draw any conclusions.
A separate investigation by European drugs regulators is already underway. [ID:nLDE67Q14B]
"This (Finnish) investigation is independent of a broader ongoing European Medicines Agency (EMA) investigation initiated in 2010," the British drugmaker said in an emailed statement.
"GSK is reviewing the report and believes it would be premature to draw any conclusions on a potential association between Pandemrix and narcolepsy until this European investigation has been completed."
Narcolepsy is a rare sleep disorder that causes a person to fall asleep suddenly and unexpectedly. Its precise cause is unknown but it is generally considered to be triggered by a combination of genetic and environmental factors.
The EMA, which regulates and reviews the safety of drugs in the European Union, said in September it was reviewing Pandemrix after reports of a link between the vaccine and cases of narcolepsy but there was no evidence so far to confirm a link. [ID:nLDE68M1R4]
An EMA spokeswoman said on Tuesday the safety review was continuing. "There is really not enough data at this point in time to determine anything," she said. "For the time being ... the benefit-risk balance of Pandemrix remains positive."
The Finnish report said that during 2009 and 2010, 60 children and adolescents aged four to 19 years fell ill in Finland with narcolepsy. Of those who fell ill, 52, or almost 90 percent, had received Pandemrix, it said, and the vaccine coverage in the entire age group was 70 percent.
Hanna Nohynek, the NIHW's vaccine safety officer, said the baseline risk for narcolepsy in children aged between four and 19 was less than 1 per 100,000 and the study found that among those who had the Pandemrix vaccine the risk rose to 8.1 per 100,000.
According to GSK, more than 31 million doses of Pandemrix have been administered worldwide in 47 countries. The company said it had received reports of a total of 162 cases of narcolepsy as of January 31, 2011, with 70 percent of these cases of narcolepsy originating from Finland and Sweden.
The Finnish institute said it would seek to confirm its findings in further investigations to be finalised by August 2011. (Editing by Greg Mahlich)