New research into a gel designed specifically to protect women from HIV infection has found that it does not work.
The anti-HIV gel Carraguard, a carrageenan-based compound made from seaweed extract, was tested in a two-year study involving more than 6,000 sexually active HIV-negative women in South Africa.
In women given Carraguard, the HIV incidence rate was 3.3 per 100 woman-years (134 infections), while in the group given a placebo, it was 3.8 per 100 woman-years (151 infections).
The study concludes that Carraguard does not protect women from HIV infection, although its authors say that urgent efforts to create an effective female-controlled HIV-prevention method should continue.
Researchers Stephanie Skoler-Karpoff and Barbara Friedland, writing in The Lancet, conclude: "This study did not show Carraguard's efficacy in prevention of male-to-female transmission of HIV, although no safety concerns were recorded.
"Low levels of gel use could have compromised the potential to detect a significant protective effect.
"Although the results from this and other completed microbicides efficacy trials have been disappointing, the search for female-controlled HIV-prevention methods must continue."
More than 33 million people worldwide are living with HIV, with more than two thirds of those in sub-Saharan Africa where women and girls account for 61% of all infections.