In certain African and Asian countries, researchers had noted that significant variations in HIV prevalence seemed to be associated with levels of male circumcision. In areas where circumcision was common, HIV prevalence tended to be lower; conversely, areas of higher HIV prevalence overlapped with regions where male circumcision was not commonly practised. It was these observations that led to the establishment of large clinical trials in African men to test whether circumcision would reduce the subsequent risk of HIV infection.

There is now strong evidence from three randomised controlled trials undertaken in Kisumu, Kenya, the Rakai District of Uganda, and Orange Farm, South Africa that male circumcision reduces the risk of heterosexually acquired HIV infection in men by approximately 60%.^[1][2][3] 

Both the Kisumu and Rakai trials randomised adult, HIV-negative heterosexual male volunteers to either be circumcised (by a medical professional at a clinic) or to no intervention. In both study arms, participants were extensively counselled in HIV prevention and risk reduction techniques.

The clinical trial in Kisumu included 2,784 HIV-negative men and showed a 53% reduction of HIV acquisition in circumcised men relative to uncircumcised men. The Rakai study results of 4,996 HIV-negative men showed that in circumcised men, HIV acquisition was reduced by 48%.

The findings reinforce the message of a South African study halted in early 2005 after researchers from the French Agence Nationale de Recherches sur le Sida (ANRS) found a 60% reduction in the risk of acquiring HIV over 21 months of follow-up in men who were circumcised at the beginning of the study.

An additional finding from the Rakai study was that men at higher risk of HIV infection appeared to derive the greatest protection from circumcision and that the risk of genital ulcers was reduced by 47% in circumcised men^[4][5].

Because HIV-positive men with CD4 cell counts below 350 cells/mm³ were excluded from the study, it may not be a true comparison of the safety of circumcision in HIV-positive and HIV-negative men.

One disturbing observation made in an interim analysis from the Rakai Health Sciences Program Data and Safely Monitoring Board was that there might be a heightened risk of HIV transmission to female partners of recently circumcised men if sexual activity takes place before the surgical wound was completely healed. 

Because of weakened immunity, HIV-positive individuals may have a higher risk of post-operative infection or a slower rate of healing. In the Rakai study, there was a trend for post-circumcision adverse events to be associated with the resumption of sexual activity before full healing had been achieved, in both HIV-infected and uninfected individuals.^[6]

HIV transmission took place in 25% (3/12 women) of the couples who engaged in sexual activity before a physician had “certified” the man as being healed. In couples who abstained from sexual activity until wound healing was complete, transmission took place in 11% (6/55 women). In those couples where the man did not undergo circumcision, ~9% of the women became HIV-infected in the six-month study period (4/46 women).

Projected effect on the HIV epidemic

An analysis using data from UNAIDS and the South African study estimated that if the full effect seen in the South African study were to be replicated when circumcision is taken up widely, three million HIV infections could be averted in Africa by 2026.^[7]

Circumcision is less common in eastern and southern Africa, although there are significant local variations. Some countries, such as Lesotho, have already begun investigating the feasibility of offering circumcision to adult males and have found a high level of demand. It is anticipated that news of these results will heighten interest in male circumcision from governments, non-governmental institutions, and the public in a number of countries, in addition to increasing demand for male circumcision services.

A mathematical model shows that universal circumcision would have the greatest impact on HIV incidence, but that targeting circumcision at men with the most sexual partners, and those aged between 20 – 30-years would be the most effective way of reducing HIV prevalence.

Modelling data on the effects of circumcision on HIV prevalence and incidence between 2007 and 2020 has also been developed by researcher Gregory Londish of the University of New South Wales, Sydney. His simulations predict that complete male circumcision in an average country could reduce HIV prevalence in 2020 from 8.3% to 5.3% and incidence from 13.5 seroconversions per thousand to 7.3 per thousand.^[8]

Targeting only 20 to 30 year old men or men with greater sexual activity produced the most cost-effective reduction in HIV prevalence, 2.0% and 1.1% respectively.