Research reveals that Pandemrix, a vaccine used in response to the pandemic from 2009, increased children’s risk of narcolepsy – a chronic condition which causes excessive daytime sleepiness.
For every 55,000 doses delivered, around one child developed the condition, health experts said.
At the height of the pandemic, between October 2009 and March 2010, almost one million children in England and Scotland aged six months to 16 years were given the vaccine.
The jab was also administered to many more people when supplies of the seasonal flu vaccine diminished – 170,000 people, including children, were given the injection between October 2010 to February 2011.
But health experts cautioned that the many children who received the jab are well and are expected to “remain fine” as symptoms appear to develop a few months after the vaccine is given. The injection has not been in use for almost two years.
The research, published in the British Medical Journal, examined 75 children aged between four and 18 who were diagnosed with narcolepsy from January 2008 and who attended sleep centres across England.
Researchers from the Health Protection Agency (HPA) and Papworth and Addenbrooke’s hospitals in Cambridge found that 11 of these had received the vaccine before their symptoms began.
Lead author Professor Liz Miller, a consultant epidemiologist with the HPA, said: “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.
“However, this risk may be overestimated by more rapid referral of vaccinated cases. Long term follow up of people exposed to Pandemrix is needed before we can fully establish the extent of the association. “Our findings have implications for the future licensing and use of adjuvanted pandemic vaccines. ”
Study co-author Dr John Shneerson, consultant physician from the Respiratory Support and Sleep Centre at Papworth Hospital in Cambridge, said: “Narcolepsy is thought to be due to a loss of function of a small group of cells in one of the sleep centres in the brain, as a result of an abnormal reaction of the body’s immune system.
“Pandemrix may have triggered an immune reaction against the sleep centre cells in those children who were genetically predisposed to develop narcolepsy.”
A Department of Health spokesman said: “The decision to recommend that children got this vaccine during the flu pandemic was based on evidence available at the time, along with the advice from the European Medicines Agency which approved its use.”