The World Health Organization has called for an investigation into GlaxoSmithKline’s H1N1 2009 vaccine, as it is believed to cause chronic sleep disorder narcolepsy.

The group’s Global Advisory Committee on Vaccine safety said that 12 countries had reported cases of the condition in children and adolescents following vaccination of pandemic swine flu product Pandemrix.

More than 31 million doses of the vaccine have been administered in 47 countries. In Iceland, Sweden and Finland, higher rates of the sleep disorder have been reported than in other countries.

Last week, a systemic review in Finland found that there is a higher risk of developing the condition among four-19-year-olds, reports the PharmaTimes.

But in an emailed statement to the publication, a spokesman for GlaxoSmithKline said that “it would be premature to draw any conclusions on a potential association between Pandemrix and narcolepsy” until an ongoing investigation by the European Medicines Agency, separate from that in Finland, is complete.

Narcolepsy is characterised by excessive daytime sleepiness in which a person experiences extreme fatigue and possibly falls asleep at inappropriate times.