The Swedish Medical Products Agency (Läkemedelsverket) ordered the massive study to determine if the vaccine had any connection to narcolepsy after dozens of reported cases of young people coming down with the affliction after receiving a swine flu jab.
The study, which took place between October 2009 and the December 2011, compared 3.3 million vaccinated Swedes with 2.5 million who were not vaccinated.
"We can see that over the whole study period we have 126 cases of those vaccinated getting narcolepsy," Ingemar Person, professor behind the study, said in a statement on Tuesday.
"There were 20 cases among those not vaccinated. We're talking about a threefold increase in risk."
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