The study, presented Tuesday by the Medical Products Agency (Läkemedelsverket), showed that children and adolescents under 20 vaccinated with Pandemrix could be up to four times as likely to develop narcolepsy than those not inoculated.
That means three cases out of every 100,000 that could be linked to the vaccination.
These results are similar to those presented by a recent Finnish study, which found that the risk of children suffering from narcolepsy was nine times higher for those vaccinated with Pandemrix.
However, the analysis is still uncertain as the new study doesn’t show whether children who already had an increased risk of developing narcolepsy were more extensively vaccinated against swine flu than those who didn’t.
The Medical Products Agency will now continue the inquiry in order to investigate why there is an increased risk of narcolepsy connected with Pandemrix.
“Part of this is looking at the actual cases, to collate information and map out all new Swedish cases diagnosed 2009-2010 with aid of medical data and expert assessments,” they wrote in a press release.
The findings of this inquiry will be presented in the summer.
A further study will be conducted by Karolinska Institutet, together with medical institutions of eight other EU-countries, where narcolepsy patients will be compared to healthy patients, in order to find out if the vaccine alone can be linked to the increased risk of narcolepsy or if there are other factors that should be taken into consideration.
Narcolepsy is a rare sleep disorder causing its sufferers to fall asleep suddenly and unexpectedly.
Since August 2010, at least 12 countries have reported cases of narcolepsy, particularly among children and adolescents, after receiving a swine flu, or H1N1, vaccine.
Figures from Sweden’s National Board of Health and Welfare (Socialstyrelsen), show that 31 million people have been vaccinated with Pandemrix in Europe.
According to the WHO, the rates of narcolepsy reported in Sweden, Finland and Iceland were higher than those in other countries.