A study conducted in Sweden has found that only certain lots of the Pandemrix swine flu vaccine were associated with increased narcolepsy in that country.
Of the 35 consignments of the vaccine against the H1N1 virus, which were delivered to Sweden, only 12 were linked with a higher incidence of narcolepsy than usual, according to a study by the Swedish Narcolepsy Association.
About 220 people in Sweden contracted narcolepsy after taking the swine flu vaccine.
The Pandemrix vaccine was also used in Finland during the swine flu pandemic of 2009-2010, and about 100 children and young people who took the vaccine later came down with narcolepsy.
The Finnish News Agency (STT) quotes sources at the National Institute for Health and Welfare (THL) as saying that no correlation between specific lots of Pandemrix and narcolepsy were found in 2010.
Last year’s cases are still being studied, and results would come by the autumn.
In Sweden, the study by the Narcolepsy Association is being investigated in the country’s Medical Products Agency.
The agency has previously denied suggestions that there would be a linkage between narcolepsy and specific lots of the vaccine.
“We need to clarify the matter once again”, said Maraia Szirmai of the Swedish Medical Products Agency to the newspaper Göteborgs-Posten.
The study by the Swedish Narcolepsy Association found that there were an unusually large number of children diagnosed with narcolepsy in specific parts of Sweden, suggesting that certain lots of the vaccine caused more problems than others.