Source: National Institute of Allergy and Infectious Diseases (NIAID)
"The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), announced an early end to two clinical trials of adult male circumcision because an interim review of trial data revealed that medically performed circumcision significantly reduces a man's risk of acquiring HIV through heterosexual intercourse. The trial in Kisumu, Kenya, of 2,784 HIV-negative men showed a 53 percent reduction of HIV acquisition in circumcised men relative to uncircumcised men, while a trial of 4,996 HIV-negative men in Rakai, Uganda, showed that HIV acquisition was reduced by 48 percent in circumcised men"
Questions and Answers: NIAID-Sponsored Adult Male Circumcision Trials in Kenya and Uganda
Statement on Kenyan and Ugandan trial findings regarding male circumcision and HIV (World Health Organization)
Randomized, Controlled Intervention Trial of Male Circumcision for Reduction of HIV Infection Risk: The ANRS 1265 Trial (PLoS Medicine)