A vaccine targeting a deadly strain of meningitis proved to be safe and highly effective in protecting African children, researchers said on Friday, raising hope that it may help prevent epidemics that afflict many African countries.

The new vaccine targets A Neisseria meningitidis, a leading cause of bacterial meningitis in Africa's so-called "meningitis belt," a group of 21 countries in sub-Saharan Africa. Researchers from the Meningitis Vaccine Project said the new vaccine produced an antibody response that was 20 times greater than current vaccines.

"The length of time individuals will be protected is probably measured in decades rather than in years," said Dr. F. Marc LaForce, director of the Geneva, Switzerland-based Meningitis Vaccine Project, in a telephone interview.

The group is a partnership between the World Health Organization and the Seattle-based PATH, an international nonprofit.

Existing vaccines do not offer long-lasting protection and do not protect very young children, he said.

The new vaccine is made by the private Serum Institute of India Ltd.

Researchers compared the new vaccine to an older one in a study of 601 children in Mali and Gambia aged 12 to 23 months. ,P> LaForce said the improved antibody response came after only one dose, suggesting it may change how African countries fight meningitis. The trial is still underway and patients will receive a second dose. There were no reported safety problems after four weeks.

"This is a very potent vaccine that can be used prevent rather than proactively treat," he said.

The next step is to study the vaccine in 2- to 29-year-olds -- the target population for most of the group's planned mass vaccination efforts. Testing will take place in Mali, Gambia, and at least one other African country.

If all goes well, next year the group hopes to immunize the entire population of those aged 1 to 29 from an African country experiencing a high degree of disease, he said.

The group is hoping the vaccine may be able to protect an entire population, including those who have not been vaccinated.

If it works, LaForce thinks the vaccine could be available in Africa for about 40 cents per dose within the next two to three years.

Meningitis is an infection of the thin lining that surrounds the brain and spinal cord. Meningitis groups A, B, and C cause most of the cases worldwide, but group A causes deadly epidemics every 8 to 10 years in an area of Africa that spreads from Senegal and Gambia in the west to Ethiopia in the east.

The largest epidemic in this region in 1996-1997 struck 250,000 people and killed 25,000.