WASHINGTON -- The hepatitis B vaccine does not cause multiple sclerosis or related neurological disorders, and it prevents a serious infection that can cause fatal liver cancer, Reuters quoted experts as saying on Thursday.

The report, issued by the Institute of Medicine, is the third in a series of reports by experts who are looking at vaccines to see if they may cause serious side-effects in the population.

Hepatitis B is a virus transmitted in body fluids, and can be passed on sexually, by sharing needles, in hospitals or via transfusions. It can damage the liver and even cause liver cancer, liver failure and death.

More than 1 billion people worldwide are infected, and one in 20 Americans carries the virus. U.S. children are now routinely vaccinated against the virus because of the risk.

But some people have feared the vaccine may cause serious side-effects, including the development of multiple sclerosis.

MS is caused when the immune system, for unknown reasons, attacks the nerve fibers. It can cause fatigue and eventually completely debilitate a patient. MS affects as estimated 300,000 Americans.

The hepatitis B vaccine has also been linked with Guillain-Barre syndrome, a somewhat similar disease that affects 100,000 people.

Such diseases affect the myelin, the fatty coating of the nerves. When it is stripped off, the nerves cannot conduct their electrical signals properly and patients lose movement and coordination.

"Hepatitis B vaccine policy has been viewed skeptically by some because of concerns about vaccine safety and a perception that the virus itself does not pose a serious risk," Dr. Marie McCormick of the Harvard School of Public Health, who led the study, said in a statement.

---- No Strong Evidence ---- She said her committee of 14 experts held meetings and reviewed studies. They heard about how serious hepatitis B is, and looked at the purported way that the vaccine could cause MS and other neurological disorders.

They found no strong evidence to suggest the vaccination could cause such diseases, but recommended that experts keep an eye on their pattern and incidence.

"Hopefully our report will ease the concerns of adults who need to be immunized against hepatitis B and are worried about the risk of multiple sclerosis," McCormick said.

The Centers for Disease Control and Prevention estimates that without widespread vaccination, more than 18,000 U.S. children would have been infected with hepatitis B and 3,000 would have eventually died from cirrhosis or liver cancer.

The Institute of Medicine, one of the national academies of sciences, was set up to advise the U.S. government on health issues. In February McCormick's panel found no link between multiple childhood vaccinations and Type I diabetes, pneumonia, meningitis or other infections.

Last year it reported no strong evidence that the combined measles, mumps and rubella vaccine may cause autism.

Some activist groups campaign against routine vaccination, saying the risks are too high, but doctors are united in saying immunization has saved millions of lives and transformed medicine. Side-effects are inevitable, they say, but rare, and much less serious than the risk of disease.