For the first time, a woman-controlled product, the PRO 2000 vaginal gel,  has been shown to give some protection to women from getting HIV during sex.

However, the protection is far from complete. The gel cuts HIV risk by 30 per cent - or by 36 per cent if women who went off the gel during a pregnancy are excluded.

This is the first real success after a frustrating string of failures with other products that promised to give women the means to protect themselves against getting HIV from a male sex partner.

"The study, while not conclusive, provides a glimmer of hope to millions of women at risk for HIV, especially young women in Africa," study leader Salim S Abdool Karim, director of South Africa's AIDS research centre, has said in a news release.

Karim and his colleagues enrolled more than 3,000 sexually active women from the US, Malawi, South Africa, Zambia, and Zimbabwe. Some of the women used the PRO 2000 product, which blocks the cellular doorway HIV uses to enter cells.

Other women used the BufferGel product, which was not effective. The two active gels were compared to no gel or to a placebo gel.

Women in the study were encouraged to have their partners wear condoms during sex and were provided condoms for this purpose.

Although condom use was high, women who used the gel reported less condom use by their partners. That was a troubling signal that overconfidence in protective gels might reduce use of a much more reliable means of preventing HIV transmission.

The NIH-sponsored trial did not prove PRO 2000 effective. That will be up to a larger, UK-sponsored trial involving nearly 9,400 women in Africa. That study should be finished by the end of the summer.