Scientists from the Center for the AIDS Program of Research in South Africa, which produced the gel, from left, Koleka Mlisana, Leila Mansoor, Janet Frohlich and Senge Sibeko

South African researchers at the international AIDS conference in Vienna, Austria have announced major progress in the fight against the disease. The researchers say their study shows a vaginal gel substance reduced the risk of HIV infection among women who used it.

The gel contains tenofovir. This is a common anti-retroviral drug used to treat people with HIV, the virus that causes AIDS.

The study was done by South African scientists with the Center for the AIDS Program of Research in South Africa. It involved almost 900 sexually active women between the ages of 18 and 40.

All were from KwaZulu-Natal, South Africa. Half were given the gel containing tenofovir. The other half were given a gel without an active substance. They were told to use the gels 12 hours before sexual intercourse and again within 12 hours after sex.

Both groups were told the gels were experimental. They were advised to use another form of HIV prevention.

The study lasted 30 months. Women who used the tenofovir gel reduced their risk of HIV infection by 39 percent. And the study found that the women who used the gel more often had even better results. Women who used the gel more than 80 percent of the times when they had sex had 54 percent fewer HIV infections.

The scientists say the tenofovir gel was also effective against another sexually spread disease. The gel reduced the rate of infection of herpes simplex-two by 51 percent.

Health experts say the results of the study show that tenofovir gel can empower women. They say it will enable them to protect themselves from HIV infection when involved with sexual partners who refuse to wear condoms.

However, researchers say they will study why the gel did not protect in all cases. Some scientists say the amount of tenofovir in the gel may be too low. Others say some women may have had sex with infected men who had very high amounts of the virus. Still others said some women may have had vaginal conditions that made them more likely to become infected. The researchers also say they will carry out more studies to confirm the results.

And that's the VOA Special English Health Report written by Caty Weaver. Transcripts, MP3s and archives of our reports are at voaspecialenglish.com. I'm Fritzi Bodenheimer.

vaginal: relating to or involving the vagina（ 陰道的，和陰道有關(guān)的）

gel: a thick substance like jelly （膠狀物）

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（來源：VOA 編輯：陳丹妮）