The US National Institute of Allergy and Infectious Diseases (part of the US National Institutes of Health) prematurely ended two clinical trials of adult male circumcision in Kenya and Uganda because an interim review revealed that the operation significantly reduces men's risk of acquiring HIV through heterosexual sex. The trial in Kisumu, Kenya, of 2,784 HIV-negative men showed a 53 percent reduction of HIV acquisition in circumcised men compared to uncircumcised men, while a similar trial of 4,996 men in Rakai, Uganda, showed that HIV acquisition was reduced by 48%. The trial was halted prematurely so as not to endanger those uncircumcised men who volunteered to participate. Both trials reached their enrollment targets by September 2005 and were originally designed to continue follow-up until mid-2007. The findings are of great interest to public health policy makers who are developing and implementing comprehensive HIV prevention programs, said NIH director Dr. Elias Zerhouni. Circumcision performed safely in a medical environment complements other HIV prevention strategies and could lessen the burden of HIV/AIDS, especially in countries in sub-Saharan Africa where, according to the 2006 estimates from UNAIDS, 2.8 million new infections occurred in a single year, he said. Only a few weeks ago, a World Health Organization delegation of HIV experts came to Israel to study how adult male circumcision is performed safely. Israel is the world capital of adult circumcision - 22,000 male new immigrants and converts to Judaism have undergone the ritual procedure voluntarily in recent years. The WHO experts were advised that while adult male circumcision to reduce HIV transmission is important, it should also be performed on baby boys, even though the benefits would have to wait until they become sexually active. Many studies have suggested that male circumcision plays a role in protecting against HIV acquisition, said NIAID director Dr. Anthony Fauci. "We now have confirmation from large, carefully controlled, randomized clinical trials showing definitively that medically performed circumcision can significantly lower the risk of adult males contracting HIV through heterosexual intercourse. While the initial benefit will be fewer HIV infections in men, ultimately adult male circumcision could lead to fewer infections in women in those areas of the world where HIV is spread primarily through heterosexual intercourse," he said. The findings from the African studies may have less impact on the epidemic in the US, where most men have been circumcised and the prevalence of HIV is lower. Moreover, most infections among men in the US is among homosexuals for whom the amount of benefit provided by circumcision is unknown. Nonetheless, the overall findings of the African studies are likely to be broadly relevant regardless of geographic location: a man at sexual risk who is uncircumcised is more likely than a man who is circumcised to become infected with HIV.