The longstanding observation that circumcision protects against HIV infection to some degree has been confirmed in a randomized trial.

Circumcision in adult heterosexual men is as effective in preventing new HIV infections as a vaccine that is 65 percent effective rate, according to the results presented here at the 3rd International AIDS Society (IAS) Conference on HIV Pathogenesis and Treatment.

The report is based on a study of more than 3,000 sexually active men living near Johannesburg, South Africa, who described themselves as heterosexual. Researchers randomly assigned the men to one of two groups: those who accepted circumcision immediately, and those who agreed to wait 20 months for the procedure.

After 21 months, the researchers diagnosed 69 new HIV cases - 51 in the uncircumcised group and 18 in the circumcised group - said Dr. Bertran Auvert of the University Versailles Saint-Quentin in France. He calculated the efficacy of circumcision to be 65 percent.

Auvert noted that several ethics committees approved the design of this study, which was funded by the French government agency INSERM.

The researchers conducted the trial by first identifying heterosexual men between the ages of 18 and 24 who were healthy and sexually active, and who said they were willing to be circumcised if it were safe and could be proven to reduce their risk of HIV infection. These men were living in Orange Farm, a neighborhood near Johannesburg, with high rates of HIV transmission and a circumcision rate of approximately 20 percent.

Prior to this study, the researchers had conducted a feasibility pilot study that found that 70 percent of men would consider circumcision if it were beneficial and safe. Physicians conducted the procedures using local anesthetic and sterile techniques.

Because the men in the study identified themselves as heterosexual, the data concern transmission only from women to men, Auvert pointed out. He added that the findings therefore cannot be generalized to man-to-man transmission or man-to-woman transmission.