Hepatitis Shot Tied to MS, Study Suggests
Vaccine's association could be statistical fluke, expert says
MONDAY, Sept. 13, 2004 (HealthDayNews) -- Fueling the continuing debate over the safety of the popular hepatitis B vaccine, a new study suggests that it contributes to a tiny increase in the number of multiple sclerosis cases.
But a neurologist said the results may be a "statistical fluke," and the study authors don't tell adults or children to stop taking the vaccine, which prevents a potentially deadly type of liver disease.
"If you're in a population that is in any way at increased risk for hepatitis B, you should get the vaccine," said study co-author Susan Jick, an associate professor of epidemiology at Boston University. "The risk of getting hepatitis B and dying from it is much higher than the risk of getting MS."
Hepatitis B, spread through blood and body fluids, can lead to cirrhosis -- scarring of the liver -- and liver cancer. An estimated 1.25 million Americans are infected, and about 5,000 die of the chronic form of the disease each year.
High-risk groups face transmission through sex or infected needles. They include drug users, people already infected with sexually transmitted diseases, gay men, AIDS patients, and health-care workers.
While the hepatitis B vaccine is considered to be 95 percent effective and is routinely recommended for children and adolescents, it's been dogged by questions about its safety. In 1996, an outbreak of 200 cases of MS and similar diseases in France convinced French officials to stop vaccinating children.
An estimated 250,000 to 350,000 Americans, mostly women, have MS, not to be confused with muscular dystrophy. The disease appears to be triggered by a malfunction of the immune system that causes it to attack the central nervous system.
MS has a wide variety of symptoms, ranging from tingling, numbness, and pain to muscle weakness, impaired balance, and mental problems.
In the new study, researchers examined statistics in a database that has tracked the health of about 3 million residents of Great Britain since 1987. They looked for patients who were first diagnosed with MS between January 1993 and December 2000 and then checked their immunization records.
The results of the study, funded by the National Multiple Sclerosis Society, appear in the Sept. 14 issue of Neurology.
Researchers found the risk of MS grew by three times over the three years after hepatitis B vaccination. On the other hand, 93 percent of those who developed MS had never been vaccinated for hepatitis B. The study didn't calculate the risk of MS among all people who are vaccinated.
Researchers said they don't know whether the vaccine caused MS or made it appear earlier than it would have otherwise, and Jick declined to speculate on why a vaccine that prevents liver disease may contribute to a nerve disease. There is speculation, however, that the immune system plays a role.
It's also possible that other unknown factors could affect the development of MS.
The study didn't definitively connect the vaccine to the disease, but instead only suggested there's a link. And even that link may not actually exist, said Dr. Anne Cross, a neurologist at Washington University in St. Louis who co-wrote an accompanying commentary on the new study.
"This study contradicts several other large studies that did not show an increased risk of MS following the hep B vaccine," she said, "thus raising a question as to whether the results represent a real finding or a statistical fluke."
Should Americans consider curtailing their use of the vaccine, which is routinely given to several groups, including children and gay men? Jick said there's no reason for panic.
"It is important to keep in mind that hepatitis B is a serious disease. It's much more common than MS," she said. "It's always important to take into account the risks and benefits."
The U.S. Centers for Disease Control and Prevention has more on the hepatitis B vaccine.