A cancer vaccine offered to young women is not responsible for triggering multiple sclerosis, researchers say today.
Some reports have suggested a link between the HPV vaccination and multiple sclerosis or other central nervous system disorders.
These concerns have been fuelled by social and news media reports of cases occurring after HPV vaccination, say Dr Nikolai Madrid Scheller of the Statens Serum Institut, Copenhagen, Denmark, and colleagues.
The HPV vaccine is now given to teenage girls in many countries to help protect them against cervical cancer.
The researchers carried out a study of 3,983,824 Danish and Swedish girls and women, of whom 789,082 were given the quadrivalent HPV vaccination.
Participants were aged ten to 44 years and followed from 2006 to 2013 using nationwide registers.
In the seven years of follow-up, 4,322 cases of multiple sclerosis and 3,300 cases of similar diseases were diagnosed. Among these diagnoses, 73 and 90 respectively took place in the risk period of two years after vaccination. Analysis showed "no increased risk of multiple sclerosis or other demyelinating diseases associated with qHPV vaccination", the team reported in the Journal of the American Medical Association.
They write: "Our study adds to the body of data that support a favourable overall safety profile of the qHPV vaccine and expands on this knowledge by providing comprehensive analyses of multiple sclerosis and other demyelinating diseases.
"The size of the study and the use of nationwide registry data of unselected populations from Denmark and Sweden allowed adequately powered analyses that are likely generalisable.
“These findings do not support concerns about a causal relationship between quadrivalent HPV vaccination and demyelinating diseases."
More than 175 million doses of the qHPV vaccine have been given worldwide since 2006.
Scheller, N. M. et al. Quadrivalent HPV Vaccination and Risk of Multiple Sclerosis and Other Demyelinating Diseases of the Central Nervous System. JAMA 6 January 2015; doi:10.1001/jama.2014.16946
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