“WHO agrees that further investigation is required concerning narcolepsy and Pandemrix vaccine,” the World Health Organization said in a statement, referring to the disorder that causes a person to fall asleep suddenly and unexpectedly.

The agency’s Global Advisory Committee on Vaccine Safety (GACVS) is “considering all available data relating to reports of increased rates of narcolepsy” and is expected to issue a statement on its web site within the coming days.

A statement issued today by the National Institute of Health and Welfare of Finland indicated an increased risk of narcolepsy observed among children and adolescents vaccinated with Pandemrix.

The Institute concluded that the risk of falling ill with narcolepsy among those vaccinated between the ages of 4 and 19 is 9 times greater than those unvaccinated in the same age group.

It considers it probable that the Pandemrix vaccine was a contributing factor to this observed increase, but states that further investigation is required of other significant co-factors associated with the increased risk of narcolepsy.

The final report from the Finnish National Narcolepsy Task Force is expected to be issued by 31 August 2011.

The Pandemrix vaccine has been used in 38 countries worldwide during the 2009/2010 season. An increase in cases of narcolepsy has been observed only in Finland, Sweden and Iceland.

WHO spokesperson Gregory Hartl told a news conference in Geneva that 18 of the 38 countries had received the vaccine from the agency. “We have no signs whatsoever from any countries that we’ve been distributing vaccines directly to that there are any indications of narcolepsy or any other unusual adverse events,” he stated.

Recommendations for the use of seasonal 2010/2011 influenza vaccines in children and adolescents remain unchanged, WHO added.