A total of 24.4 percent of the children with MS were vaccinated for hepatitis B in the three years before the study, compared to 27.3 percent for the children without MS.
The researchers observed that the children who had developed MS were 1.74 times more likely to have received a certain type of hepatitis B vaccine, called Engerix B.
The risk was only found for this specific type of hepatitis B vaccine, and not for all vaccines against hepatitis B.
The researchers, however, admit that this observation cannot be taken to be a confirmation that the vaccine caused MS.
They say that further studies are needed to determine whether this is a causal relationship.
The study will be published in the October 8, 2008, online issue of Neurology, the medical journal of the American Academy of Neurology.