The United Nations AIDS chief predicted Thursday that a vaginal gel that protects women from contracting HIV (search) during intercourse could be ready in as little three to four years.

With the successful development of a vaccine still nowhere in sight, UNAIDS chief Peter Piot said a gel designed to thwart the transmission of the AIDS virus during sex would be the next best thing.

"Where we have better hope is something at least as important, and that is a so-called microbicide (search)," Piot said, adding there were currently about 15 HIV/AIDS microbicide products being tested around the world. "Conceptually, it's straightforward, whereas with the vaccine we still don't know where to go.

"We are, in the most optimistic scenario, I would say three years, four years away. Currently we are dealing with trials that deal with thousands and thousands of women."

The microbicide would come in the form of a gel or an ovule that's put in the vagina before intercourse and immediately kills the virus upon contact. Piot compared it to a contraceptive spermicide.

Researchers around the globe have been working on a vaccine since the discovery of the AIDS virus over 20 years ago. So far only one vaccine candidate has undergone a large-scale clinical trial, and results proved disappointing. Only two other candidate vaccines are in human trials right now, in Thailand and the United States, Piot said.

"We don't even know for a HIV/AIDS vaccine what are the elements in the immune response that protect us, what kind of antibodies should we try to stimulate," Piot said.

Nearly half the 39.4 million people infected with HIV worldwide are female. Three-quarters of all HIV-positive women live in sub-Saharan Africa. About 57 percent of the adults with HIV are women.

Women often have to rely on whether their male partner is faithful and uses a condom, Piot said. Abstinence is often not an option, especially in marriage, and negotiating the use of a condom within any relationship in any culture is difficult.

"Over half of all new infections today occur in women," Piot said. "Because of this increasing feminization of the epidemic we need ways to protect women and ways that are under the control of women, preferably one a male partner wouldn't even know the woman is using.

"Just as the contraceptive pill is really what made a difference in terms of contraception and family planning, a product like (a microbicide) — if it were not expensive, could be bought over the counter, didn't need to be kept in a fridge, etc. — could make a big difference for women's lives in the AIDS epidemic."

On another matter Piot warned that India's new patent law prohibiting domestic drug companies from making low-cost copies of expensive Western medicines would cause "big problems" in the future.

The changes in patent rights enhance the country's participation in global trade but requires it to enforce stricter patent rules for its pharmaceutical industry.

"It's not a problem for products already being used in first line treatment today. It's about the future," Piot said. "Indian companies will not be allowed under that new law to copy products still under patent.

"And we will continuously need new anti-retroviral drugs because after some time many people develop resistance to existing treatments, and if you can't switch to a new, effective medicine, you die."