Of the more than 30 million people in almost 50 countries who have received GlaxoSmithKline's ($GSK) Pandemrix, close to 800 have developed narcolepsy. And now, for the first time, a team from Finland thinks it knows why.
Comparing Pandemrix with Arepanrix, a vaccine used in Canada with the same adjuvant, the researchers found that Pandemrix had more of one structurally altered viral nucleoprotein--a disparity lead researcher Outi Vaarala attributed to the way the vaccines were prepared.
"The vaccine virus itself has components of the virus. It is also supposed to contain viral protein. There's nothing extraordinary about that," she told Yle, Finland's national broadcasting company. "The difference was that Pandemrix had one viral protein in a different form and there was more of it."
In February 2011, Finland's National Institute for Health and Welfare announced a spike in narcolepsy cases and a link between Pandemrix and the sleep disorder. Recipients of the vaccine aged between four and 19 had a "manifold" increased risk of developing narcolepsy during the 8 months following vaccination, as compared with those of the same age group who had foregone the vaccine, said the health agency.
In May 2013, researchers in Finland found that it wasn't only kids who were susceptible to narcolepsy after getting Pandemrix, but adults, too, though the findings suggested that the risk of developing narcolepsy tapers off with age.
And in September 2013, the U.K. government, which had previously turned down compensation claims for Pandemrix-related narcolepsy, changed its mind 7 months after new evidence came to light. Research published in the British Medical Journal showed an increased risk of narcolepsy in English children who had received Pandemrix.
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