The first vaginal gel designed to protect women from the AIDS virus, though safe, did not prevent infection in a study of 6,000 South African women, researchers said on Monday.

The study was marred by low use of the gel, which could have undermined results, the researchers said. Women used it less than half the number of times they had sex, and only 10 percent said they used it every time as directed.

The product, called Carraguard, is the first HIV cream to be tested in advanced trials in women and shown to be safe, raising hopes that it might be combined with drugs or other compounds to work better.

"We are disappointed that this trial did not show Carraguard to be effective; nonetheless the completion of this trial is a milestone in HIV prevention research," said Peter Donaldson, president of the New York-based Population Council, which sponsored the trial.

Carraguard, a microbicide developed by the nonprofit Population Council contains carrageenan, which comes from seaweed and is widely used in the food and cosmetics industries. Lab, animal and early human tests suggested it might prevent HIV and other sexually spread infections.

The latest study was done from March 2004 through March 2007 in Gugulethu, Isipingo and Soshanguve, all in South Africa.

More than 9,000 women, average age 31, volunteered for the study. About 27 percent tested positive for HIV and were disqualified. In all, 6,202 women were randomly given either Carraguard or a placebo gel. Neither the women nor the study staff knew who received what. All received safe-sex counseling and condoms.

"The results are comparable," with no statistically significant difference, said Khatija Ahmed, a microbiologist who headed the study's Setshaba Research Centre site near Pretoria.

However, women in the study used the gels only 44 percent of the time, and some used it hardly at all. Researchers are still analyzing the numbers to see what that means. If nonuse was far greater in the microbicide group than the placebo group, "it could have had an impact on our final study results," said Barbara Friedland, the study's behavioral coordinator.

(Agencies via Xinhua News Agency February 19, 2008)