According to a study published on Friday by The Lancet circumcision lowers the risk of HIV for men but doesn't prevent them from passing it on to women once they are infected.

Three years ago trials in Kenya, Uganda and South Africa found foreskin removal more than halved men's risk of infection by the human immunodeficiency virus (HIV) while last year a longer-term analysis of one of the trials found at 65% risk reduction, the benefit to be even greater than thought.

Now a randomized controlled trial in Rakai, Uganda tried to establish if male circumcision could also reduce the risk of HIV for women who have intercourse with an infected man. According to Maria Wawer, MD, of the Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues the answer was "No" and came as a disappointment as it contradicted earlier observational studies which indicated that partners of circumcised HIV-positive men had a lower risk of getting HIV than women whose infected partners were not circumcised. In the trial doctors enrolled 922 uncircumcised Ugandan men aged 15-49, badly infected with HIV but who did not show any symptoms. Half of the group underwent circumcision while the other half remained uncircumcised.

Women who were HIV uninfected were also enrolled in the study who were partners of the male volunteers with 90 women in the circumcised group, and 70 in the uncircumcised groups. HIV prevention training was given to all the participants. Dr. Wawer and colleagues said the trial was stopped early as its data safety monitoring committee said there was little chance continuing would demonstrate a benefit. Data analysis two years later showed that 18% of the women in the circumcised group who were examined at the follow-up point had become infected, compared to 12% in the control group.

They also noted that most of the infection in the circumcised group occurred within six months of circumcision perhaps as some of the men had intercourse without giving time for the circumcision wound to heal properly, thus exposing the woman to HIV-infected blood in the vagina. "The possibility of higher risk of transmission in couples who resumed sexual intercourse before complete wound healing cannot be excluded," the researchers said.

The doctors though disappointed with the test results said circumcision campaigns are still valid as women get an indirect advantage as the fewer the men who are infected with HIV the lesser are their chances of contracting the disease. Dr. Wawer and colleagues said condom use after circumcision remains important. Jared Baeten, MD, of the University of Washington in Seattle, and colleagues said, "Circumcision programs should make the most of the opportunity to provide condoms and risk- reduction counseling, and to offer voluntary HIV testing."

The researchers also pointed out that "for reasons of safety, we excluded HIV-infected men with CD4-cell counts less than 350 cells per µL or with WHO clinical stage 3 or 4 disease. Thus, the current study cannot establish possible effects on female partners of circumcision in men with more advanced HIV infection."

Early results of the trial were presented in Boston at the 2008 Conference on Retroviruses and Opportunistic Infections.