WASHINGTON (Reuters) - An experimental malaria vaccine is the most promising yet, protecting up to 65 percent of infants from infection in two studies in Africa, researchers reported on Monday.

Separate tests in Kenya and Tanzania showed GlaxoSmithKline’s vaccine called RTS,S could protect babies and toddlers from infection with malaria and could prevent disease even in those already infected.

While the vaccine is far from perfect, it is the best yet against the mosquito-borne parasite, the researchers agreed. They said they would begin phase III clinical tests, the last stage before seeking regulatory approval, next year.

“Even a partially effective vaccine has the potential to save hundreds of thousands of lives each year,” said Christian Loucq, director of the nonprofit PATH Malaria Vaccine Initiative, which helped to conduct the study.

“We are one important step closer to the date when malaria will join diseases such as smallpox and polio, which have been either eliminated or controlled through vaccines.”

The World Health Organization estimates malaria killed 881,000 people and infected 247 million worldwide in 2006. Some malaria experts say those numbers underestimate the problem.

The disease is especially hard to fight as people are continually infected by mosquitoes throughout their lives. The tiny parasites get into the blood and live and reproduce inside the body, causing fever and sometimes deadly brain infections.

Dr. Salim Abdulla of the Bagamoyo Research and Training Center in Tanzania and colleagues tested 340 infants, giving them three doses of the RTS,S vaccine or three doses of hepatitis B vaccine.

The malaria vaccine protected 65 percent of infants from infection with malaria during the six months of the trial, they reported in the New England Journal of Medicine and told a conference on tropical diseases in New Orleans.

YEARS OF EFFICACY

“We are very confident that the efficacy of the vaccine extends for several years,” Joe Cohen of GlaxoSmithKline Biologicals in Belgium told the briefing.

An earlier study had shown the vaccine could protect children for at least 18 months.

The children also got vaccines against diphtheria, tetanus, whooping cough and Haemophilus influenzae B as part of a World Health Organization childhood vaccination program, and the vaccines all worked well, the study showed.

“I see the effects of malaria in my country firsthand,” Abdulla told the briefing. “So these results are very exciting and give me a new hope of seeing a first generation malaria vaccine available ... in the near future.”

In a second trial, Dr. Ally Olutu of the KEMRI-Wellcome Trust Collaborative Research Center in Kenya and colleagues vaccinated 894 children aged 5 to 17 months with three doses of either a slightly different formulation of the malaria vaccine or a rabies vaccine.

The found clinical episodes of malaria fell by 53 percent.

While this is slightly different from complete protection from infection, the researchers said the point is to protect children from disease, and they felt the results were comparable.

“It is, indeed, a hopeful beginning,” William Collins and John Barnwell, malaria experts at the U.S. Centers for Disease Control and Prevention, wrote in a commentary published in the New England Journal of Medicine.

They noted that the vaccine was not yet tested in regions with the most intense malaria transmission.