Eight hundred children in Europe have developed narcolepsy after taking the swine flu vaccine, according to Reuters.
Reuters reported the children in Sweden and across Europe came down with the sleep disorder after being vaccinated with the Pandemrix H1N1 vaccine which is made by GlaxoSmithKline.
Regulators there have ruled Pandemrix should not be given to anyone under the age of 20.
Emmanuel Mignot, a Stanford University sleep disorder specialist, said "there's no doubt in my mind whatsoever that Pandemrix increased the occurrence of narcolepsy onset in children in some countries - and probably in most countries."
Everyday Health reported about 30 million people received the vaccine and that a link between the sleep disorder and Pandemrix has been under investigation since 2010.
However, the company said there was not enough information to link the two.
Meanwhile, Finland, Sweden, France, Norway and Ireland have seen a recent increase in narcolepsy, according to Everyday Health.