GlaxoSmithKline Plc (GSK)’s Pandemrix swine-flu vaccine was associated with an increased risk of narcolepsy in U.K. children for the first time in a study that supports similar findings in Finland and Sweden.
Among 75 children between the ages of 4 and 18 diagnosed with narcolepsy, 11 had been vaccinated with Pandemrix before symptoms began, seven of them within six months, scientists at the U.K. Health Protection Agency found. The study was published today in the British Medical Journal.
The European Medicines Agency in July 2011 recommended restricting the use of Pandemrix in people younger than 20 after the product was linked to rare cases of narcolepsy. More than 30 million Europeans received the treatment during the 2009 influenza pandemic. The U.K. study suggests a probability of narcolepsy for about 1 out of every 55,000 doses of Pandemrix, the HPA said in a statement.
“These findings suggest there is an increased risk in children of narcolepsy after Pandemrix vaccination, and this is consistent with findings from studies in other European countries,” Elizabeth Miller, a consultant epidemiologist with the HPA and lead author of the study, said in the statement. “However, this risk may be overestimated by more rapid referral of vaccinated cases.”
Narcolepsy is a neurological disorder caused by the brain’s inability to regulate sleep-wake cycles, provoking bouts of sleep throughout the day. Long-term follow-up is needed to fully understand the association with Pandemrix, the researchers said.
The vaccine against the H1N1 flu virus may have triggered an immune reaction against the sleep center cells in children who were genetically predisposed to develop narcolepsy, said John Shneerson, co-author and consultant physician from the Respiratory Support and Sleep Centre at Papworth Hospital in Cambridge, England.
Glaxo first became aware of the possible link through reports of side effects in 2010, said company spokesman David Daley. More investigation is needed to disentangle other factors, including genetic and environmental ones, that are associated with the condition, he said.
“We remain committed to carrying out additional research into the potential role of Pandemrix in the development of narcolepsy,” Daley said in an e-mailed statement. “The additional data becoming available will support our ongoing research efforts and, we hope, enable us to provide more answers.”
Glaxo, the U.K.’s biggest drugmaker, is conducting a study in Canada, where an equivalent H1N1 vaccine, Arepanrix, was widely used. The company plans to report the full results of that research next year, Daley said.
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