British health officials are investigating cases of narcolepsy in children amid concerns that pandemic flu vaccinations lie behind a rise in the sleep disorder seen in other countries.
The Health Protection Agency is gathering vaccination histories and medical data on children aged four to 18 who have been assessed for narcolepsy at sleep centres in England in the past few years.
The investigation centres on the GlaxoSmithKline (GSK) vaccine Pandemrix, which was given extensively in 2009/10 during the H1N1 "swine flu" pandemic that spread around the world.
The vaccine was used very little in 2010/11 and was unavailable during the 2011/12 influenza season. Pandemrix is only used to combat pandemics and differs from the more familiar seasonal flu vaccine.
The HPA said: "There is no evidence of any association between seasonal influenza vaccines and narcolepsy."
Clinical details including dates of first symptoms and diagnoses are being obtained from clinics and GP records checked for dates of any pandemic vaccination given to the children.
The information will help the HPA identify how many children and teenagers with narcolepsy received the pandemic vaccine and spot any clustering of the disorder shortly after vaccination. The findings from the HPA study are due to be published later this year, the agency said.
The latest evidence for a link between Pandemrix and narcolepsy appears in two studies from Finland published in the journal Plos One.
The authors of the papers, Markku Partinen of the Helsinki Sleep Clinic and Hanna Nohynek of the National Institute for Health and Welfare in Finland, found narcolepsy in children under 17 averaged from 0.31 cases per 100,000 between 2002 and 2009, but rose 17-fold to 5.3 cases per 100,000 in 2010, when Pandemrix was used.
Further work revealed that in children born between January 1991 and December 2005 narcolepsy rates for those who had Pandemrix jabs were nine per 100,000, compared with 0.7 per 100,000 for unvaccinated children – almost 13 times lower.
"We can't exclude the possibility that there are simultaneous environmental factors at work here, but we can say Pandemrix was one of the factors involved," Partinen said.
He added that the overall risk from Pandemrix was low, with less than one in 10,000 people vaccinated developing narcolepsy.
Professor David Salisbury, director of immunisation at the Department of Health, said the government was aware of the Finnish data and that further UK research was underway into the risk associated with Pandemrix.
"This follows a European-wide review last year, which reached the conclusion that Pandemrix may only be used in people under 20 if the annual seasonal vaccine is not available and there is a particular need to immunise against H1N1," he said.
GSK said: "GSK fully maintains its responsibility and commitment to the highest standards of patient safety.
"It remains the case that a causal link with Pandemrix cannot be confirmed and that other unknown factors may have contributed.
"These questions need to be further clarified before definitive conclusions on an association of Pandemrix and narcolepsy can be drawn.
"GSK will continue to work closely with the European Medicines Agency and other national regulatory organisations in the best interest of patients."
