A research team from Finland thinks it knows why about 800 people out of the more than 30 million who received GlaxoSmithKline’s Pandemrix developed narcolepsy.
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 eight months following vaccination, as compared with those of the same age group who had skipped the vaccine, said the health agency.
Researchers in Finland in May 2013 found that adults also were at risk of developing narcolepsy, though the findings suggested that it decreased with age.
The U.K. government, which had previously turned down compensation claims for Pandemrix-related narcolepsy, changed its mind in September 2013, seven months after new evidence was discovered. Research published in the British Medical Journal showed an increased risk of narcolepsy in English children who had received Pandemrix.