U.S. researchers have failed in their first attempts to develop a vaccine against malaria, the world's most pervasive infectious disease.

Scientists at the Walter Reed Army Institute of Research, who have been working for years on a malaria vaccine, inoculated 15 volunteers with a vaccine cloned from the genetic material of the malaria parasite.

Six people were given booster shots and then were bitten by infected mosquitos. Two others without vaccines were also bitten. Seven of the eight contracted the disease, the researchers reported in last week's British medical journal, The Lancet, confirming preliminary indications that the effort had failed.

"We are disappointed that it took very high doses of the vaccine to develop any antibodies," said Dr. W. Ripley Ballou, a member of the vaccine project at Walter Reed. "But the approach has promise. Antibodies did develop. And to some degree they are able to protect people."

Antibodies are protein molecules that the body manufactures to neutralize invading foreign substances. Useful antibodies for malaria would seek out the dangerous parasites, bind to them and halt their progress before they could disrupt the immune system.

Once a successful vaccine creates enough antibodies in the blood, the immune system never forgets how to make them. If a new infection comes along, the antibodies spring into action, quickly disabling the invaders.