Sept. 13, 2004 --The hepatitis B vaccine series has been administered to more than 20 million people in the U.S. and more than 500 million people in the world. It is more than 95% effective in preventing an infection that kills millions annually. However anecdotal evidence has linked the vaccine to an increased risk for multiple sclerosis.
Now a new study in the Sept. 14 issue of the journal Neurology offers the some of the strongest evidence supporting the link.
In the study, researchers report that vaccination with the recombinant hepatitis B vaccine is associated with a threefold increased risk of multiple sclerosis.
They concluded that the benefits of the vaccine still appear to outweigh the risks, but added that the findings "challenge the idea that the relation between hepatitis B vaccination and the risk of MS is well understood."
"We aren't policy makers, but it is important to recognize that many lives are saved by this vaccine," researcher Susan Jick, DSc, tells WebMD. "We certainly aren't suggesting that people stop getting vaccinated. But this study raises important questions."
The actual cause of MS is still unknown but MS is believed to be an autoimmune disease in genetically susceptible persons. Reports of hepatitis B vaccination and MS were from anecdotal case reports, not scientifically controlled studies.
A Billion Doses
Approximately 350 million people worldwide are infected with hepatitis B virus, and as many as 65 million will die from liver cancer or cirrhosis of the liver as a result. The hepatitis B vaccine has generally been considered one of the safest vaccines ever produced, and more than a billion doses have been given since was first made available in the early 1980s.
Reports in the mid-1990s pointing to a link between the vaccine and MS lead the French government to temporarily suspend the routine immunization of pre-adolescents in schools, but most clinical trials have not supported the association.
Two years ago an immunization safety committee guided by the Centers for Disease Control and Prevention and the Institutes of Health reported that the clinical evidence "favors rejection of a causal relationship between hepatitis B vaccine and multiple sclerosis."
In the newly published study, researcher Miguel Hernan, MD, used a national health database from the U.K. to identify MS patients and people who had gotten the hepatitis B vaccine. Roughly 3 million Britons were registered in the database, and the researchers included only 163 of more 700 cases of MS patients and 10 times as many people who did not have MS in the analysis.
The researchers estimated that immunization was associated with a threefold increase in MS risk within the three years following vaccination.
Most With MS Weren't Vaccinated
While conceding that the new study was well designed and well executed, University of Washington neurology professor Anne H. Cross, MD, argues that the exclusion of so many MS patients in the analysis could have been a factor in the outcome. Of 713 MS cases identified, the researchers included only 163 in their study and just 11 of these developed first symptoms of MS within three years of vaccination.
"One must consider whether this selection process, which was deemed necessary to properly perform the study, might have led to some unrecognized bias," Cross wrote in an editorial she co-authored.
It makes little sense, she says, that the hepatitis B vaccine causes MS when there is no evidence linking the virus to the disease.
"The vaccine is just a peptide (a small protein) of the virus, so it stands to reason that if there is a link between the vaccine and MS there would also be a link between hepatitis B virus infection and MS," she tells WebMD.
She also pointed out that more than 90% of the multiple sclerosis patients in the database had not been vaccinated against hepatitis B.
The hepatitis B vaccine is now routinely given to infants in the U.S. as a series of shots, and CDC spokesman Eric Mast, MD, MPH, noted that there is no evidence linking the vaccine to MS or any other neurological disease in children.
Mast, who is acting director of the division of viral hepatitis, tells WebMD that even with the addition of the newest study, the clinical evidence does not support a link between the hepatitis B vaccine and MS.
"This has certainly been on our radar screen, and we need to continue to look at it," he says. "But the preponderance of evidence suggests no association."