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Friday, November 12, 2004

Hepatitis B vaccine and the risk of multiple sclerosis

WHO - "Recombinant hepatitis B vaccine and the risk of multiple sclerosis"

Why is the issue of an association between hepatitis B vaccination and multiple sclerosis surfacing again?

The possible role of vaccination against hepatitis B in the occurrence of multiple sclerosis (MS) is being raised again as a result of the recent publication of a new study (Hernan et al., Neurology , 2004), which revives questions raised ten years ago.

American Academy of Neurologists --

Hepatitis B vaccine may be associated with increased risk of multiple sclerosis

The popular hypothesis that the hepatitis B vaccine is associated with an increased risk of multiple sclerosis has been scientifically corroborated through a prospective study of patients in the United Kingdom. Results of the study, and a related editorial, are reported in the September 14 issue of Neurology, the scientific journal of the American Academy of Neurology.

More than 350 million people worldwide are chronically infected with the hepatitis B virus. Of these, 65 million will die from cirrhosis or liver cancer – approximately 5,000 per year in the United States. The hepatitis B vaccine, considered one of the safest vaccines ever produced, is more than 95 percent effective in preventing chronic hepatitis B infection, and is the first vaccine against a major human cancer.

In 1996, about 200 cases of MS (and other central nervous system demyelinating disorders) following hepatitis B vaccination were reported in France, prompting the French government to suspend routine immunization of pre-adolescents in schools. The potential link between vaccination against hepatitis B and an increased risk of MS has since been evaluated in several studies, with limited success.

Miguel Hernán, MD, DrPH, of Harvard School of Public Health, Boston, led a team of researchers in conducting a study using the General Practice Research Database (GPRD) in the UK. The GPRD tracks many aspects of healthcare utilization, treatments, and adverse events in the UK, and comprises five percent of the UK population, or three million Britons, with data starting from 1987.

Using the GPRD, researchers identified patients who had a first MS diagnosis recorded between January 1993 and December 2000, and immunizations data was obtained from the computer records. “Our analyses include 163 cases of MS and 1,604 controls,” noted Hernán. “We estimated that immunization against hepatitis B was associated with a three-fold increase in the incidence of MS within the three years following vaccination.”

Hernán cautions that any considerations regarding the administration of hepatitis B vaccine must take into account the large benefits derived from the prevention of a common and potentially lethal infection. “Our study cannot distinguish whether the vaccine hastens the onset of MS in persons destined to develop the disease years later, or whether it causes new cases of MS in susceptible individuals. It is also important to stress that 93 percent of the MS cases in our study had not been vaccinated,” concluded Hernán. Further research is required to determine the reasons for the association between hepatitis B vaccine and MS.

The study was supported by a grant from the National Multiple Sclerosis Society.

The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as stroke, Alzheimer's disease, epilepsy, Parkinson's disease, autism and multiple sclerosis.


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