For the first time, a vaginal gel has proved capable of blocking the AIDS virus: It cut in half a woman's chances of getting HIV from an infected partner in a study in South Africa. Scientists called it a breakthrough in the long quest for a tool to help women whose partners won't use condoms.
The results need to be confirmed in another study, and that level of protection may not be enough to win approval of the microbicide gel in countries like the United States, researchers say. But they are optimistic it can be improved.
''It's the first time we've ever seen any microbicide give a positive result'' that scientists agree is true evidence of protection, said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases.
The gel, spiked with the AIDS drug tenofovir, cut the risk of HIV infection by 50 percent after one year of use and 39 percent after 21/2 years, compared to a gel that contained no medicine.
To be licensed in the U.S., a gel or cream to prevent HIV infection may need to be at least 80 percent effective, Fauci said. That might be achieved by adding more tenofovir or getting women to use it more consistently. In the study, women used the gel only 60 percent of the time; those who used it more often had higher rates of protection.
The gel also cut in half the chances of getting HSV-2, the herpes virus that causes genital warts.
Even partial protection is a huge victory that could be a boon not just in poor countries but for couples anywhere when one partner has HIV and the other does not, said Dr. Salim Abdool Karim, the South African researcher who led the study. In the U.S., nearly a third of new infections each year are among heterosexuals, he noted.
He will present results of the study today at the International AIDS Conference in Vienna. The research was published online Monday by the journal Science.
''We now have a product that potentially can alter the epidemic trends ... and save millions of lives,'' said Dr. Quarraisha Abdool Karim, the lead researcher's wife and associate director of the South African program that led the testing.