The swine flu shot from GlaxoSmithKline's called Pandemrix has been linked to cases of narcolepsy in children, a rare sleep disorder. The scientific study in England confirms similar findings throughout Europe.
Pandemrix has been administered to more than 30 million individuals during the H1N1 flu pandemic in 2009-2010. It contains a component which may have triggered an adverse reaction in the immune system of some children at higher genetic risk of narcolepsy, scientists said in new research published on Wednesday.
The study published in the British Medical Journal reveals a 14-fold increased risk with implications for the future licensing and use of the component in pandemic vaccines.
Narcolepsy is thought to be an autoimmune disease, apart from being a life-long disorder with symptoms that can include daytime sleepiness, hallucinations and cataplexies.
The GSK says more than 800 cases linked to the shot have been reported in Europe.
The British drug making company spokesperson said the company is to research the issue and understand the potential role of Pandemrix in the development of narcolepsy. He also added that GSK believes the amount of information is still not enough to associate Pandemrix with narcolepsy.
An adjuvant called AS03 is the focus of scientists now. They are investigating the link and analyzing the role of the component. The UK results revealed so far that the Pandemrix shot administered at any time was associated with a 14-fold increased risk of narcolepsy, whereas vaccination within six months before onset of the disease was associated with a 16-fold increased risk.
The research team leader, Liz Miller, a consultant epidemiologist with the HPA said the risk may be overestimated because vaccinated children may have been referred to specialist sleep clinics more rapidly.
One in 50 000 may have been affected by narcolepsy due to the shot, scientists said. The number is lower than in countries such as Sweden and Finland where Pandemrix was used more widely and the risk was around one in 16 000 to 17 000 children who have been vaccinated.
In 47 mainly European countries more than 30 million doses of the GSK vaccine were administered during the H1N1 pandemic and the shot never reached the US.
The UK researchers studied 75 children ages 4 to 18 diagnosed with narcolepsy from January 2008 and who attended sleep centers across England. 11 of them were vaccinated with Pandemrix prior to symptoms. A researcher stressed that Pandemrix is the only link to this problem.
Experts say around a quarter of Europeans have a genetic profile making them more susceptible to the incurable narcolepsy disorder. Specialist doctors say symptoms can be treated with drug combinations aimed at re-regulating the sleep-wake cycle.