Swine flu vaccine can escalate the risk of a sleep disorder in children, researchers say.
A team of researchers from England initiated to examine the safety of the A/H1N1 influenza vaccine Pandemrix that was provided during the 2009 epidemic in the country.
They found children and teens who received the vaccine experiencing a sleep disorder known as narcolepsy.
Narcolepsy is a nervous system sleep disorder characterized by excessive sleepiness and repeated daytime sleep attacks. People suffering from narcolepsy experience sudden muscle weakness known as cataplexy. Cataplexy is often caused by strong emotions like laughter or anger. Factors that lead to the sleep disorder are yet to be fully known.
The pandemic in 2009 claimed more than 18,000 lives in 200 countries across the globe. In England, between October 2009 and March 2010, a significant number of children, both from the healthy group (24 percent) and risky group (37 percent), received the vaccine.
The safety of the vaccine was first questioned by some experts in Finland and Sweden. A 2012 study conducted in Finland found the vaccine making children and the young generation at a 13-fold higher risk of the sleep disorder.
For the current study, researchers included 245 children aged between 4 and 18, who were undergoing treatments at various sleep centers and child neurology centers in England. Supporting previous findings, they found about one in every 52,000 or 57,500 children who received the vaccination developed narcolepsy.
"The increased risk of narcolepsy after vaccination with ASO3 adjuvanted pandemic A/H1N1 2009 vaccine indicates a causal association, consistent with findings from Finland. Because of variable delay in diagnosis, however, the risk might be overestimated by more rapid referral of vaccinated children," the authors wrote, according to a news release.
According to the authors, vaccinating a kid anytime (14-fold higher risks) or before the symptoms appear (16-fold higher risks) can increase the risks of narcolepsy.
"Further studies to assess the risk, if any, associated with the other A/H1N1 2009 vaccines used in the pandemic, including those with and without adjuvants, are also needed to inform the use of such vaccines in the event of a future pandemic," the authors suggest.
Results of the study have been reported in the British Medical Journal (BMJ).
