London: Children vaccinated with the pandemic H1N1 swine flu shot were 13 times more likely to develop narcolepsy, a condition characterised by excessive sleepiness, even during daytime.
Finnish researchers found that between 2002 and 2009, before the swine flu pandemic struck, the rate of narcolepsy in children under 17 years was 0.31 per 100,000.
In 2010 this was about 17 times higher at 5.3 per 100,000 while the narcolepsy rate remained the same in adults, the journal Public Library of Sciences One reports.
Markku Partinen of the Helsinki Sleep Clinic and Hanna Nohynek of the National Institute for Health and Welfare in Finland, also collected vaccination and childhood narcolepsy data for children born between January 1991 and December 2005, according to the Telegraph.
They found that the rate of narcolepsy in those who were vaccinated was nine per 100,000 compared to 0.7 per 100,000 in unvaccinated children, or 13 times lower.
Pandemrix was the main vaccine used in the UK against the swine flu epidemic in which six million people were vaccinated. It was formulated specifically for the swine flu pandemic virus and is no longer in use.
The World Health Organisation has conducted an investigation after the link was first suggested in Finland and Sweden two years ago and found no other countries experienced a increase in narcolepsy rates during or after the pandemic.
Sir David Salisbury, director of immunisation at the Department of Health, UK said: "The Department of Health is aware of the Finnish data, and keeps all new evidence under review."