Two randomized, controlled trials in Africa on the effect of adult male circumcision on HIV transmission, conducted by researchers from Canada, Kenya, Uganda, and the United States, were halted last month when an interim review of the trial data showed that the procedure significantly reduces a man's risk of becoming infected with HIV through heterosexual intercourse.
In a trial in Kenya involving 2784 HIV-negative men, 47 uncircumcised men became infected compared with 22 among the circumcised men, a 53% reduction. In a trial in Uganda involving 4996 HIV-negative men, 43 uncircumcised men acquired HIV compared with 22 among the circumcised men, a 48% reduction.
Stephenson J. Circumcision and HIV. JAMA. 2007;297(3):254. doi:10.1001/jama.297.3.254-c