People who are vaccinated against hepatitis B are at an increased risk of developing multiple sclerosis (MS), according to a study of UK patients.

American public health experts discovered a link between the vaccine and MS when they examined records of more than 1,500 people. The research team does not know if the vaccine causes MS of those already susceptible to the disease or if it speeds up the onset.

Hepatitis B is a virus that could lead to liver problems, and possibly, liver failure. It usually is passed by blood contact, but the virus also is present in saliva and other bodily fluids. UK doctors encourage patients who are at an increased risk for the disease to get immunized. Medical professionals, prison staff and inmates, people who share drug needles and those with several sexual partners are among those at the highest risk of getting hepatitis B.

In the 1990s, there was some evidence that supported the link between the vaccine and MS; however, other studies disputed this. Still, the idea spurred further research.

In this study, researchers looked at UK patients diagnosed with MS from 1993-2000 and compared hepatitis B vaccination records of the 163 MS patients to about 1,600 control group patients without the disease. Investigators estimated there was a three-fold increase in the incidence of MS within three years of being administered the shot.

Liver disease groups warn that the study' results may have holes because vaccination records for the control group may not have included workplace vaccinations. If so, then the incidence of MS would go down significantly.

Despite the controversy, experts say that this is an important study that needs to be considered in future research.

BBC News September 14, 2004