Observational studies suggested that male circumcision reduces heterosexual human immunodeficiency virus (HIV) acquisition in men,12
a finding supported by 3 large randomized controlled trials of more than 10 000 men conducted in South Africa, Kenya, and Uganda. The trials enrolled HIV-negative men and randomized them to circumcision upon enrollment or after 21 to 24 months. All 3 trials demonstrated that male circumcision significantly decreased male heterosexual HIV acquisition by 50% to 60%,13-15
despite differences in age eligibility criteria, urban vs rural settings, and surgical procedure (). The South African trial, which enrolled 3128 men aged 18 to 24 years in a periurban township, found an intent-to-treat efficacy of 60% (95% confidence interval [CI], 32%-76%).15
The Kenyan trial enrolled 2784 men aged 18 to 24 years in an urban setting and found an intent-to-treat efficacy of 53% (95% CI, 22%-72%).14
The Ugandan trial enrolled 4996 males aged 15 to 49 years in a rural setting and found an intent-to-treat efficacy of 57% (95% CI, 25%-76%)13
; furthermore, the protective effect of circumcision increased with longer time from surgery. All 3 randomized trials were consistent with previous ecological and observational studies in Africa, Europe, and the United States.16
Owing to this new evidence, the World Health Organization in conjunction with the Joint United Nations Program on HIV/AIDS recommended that male circumcision be provided as an important intervention to reduce heterosexually acquired HIV in men.17
Male Circumcision and HIV and STI Acquisition in Men and Transmission to Female Partners
There are concerns that the results of the 3 African randomized controlled trials of heterosexually acquired HIV in men may not be applicable within the United States, where more than 1 million individuals are living with HIV/AIDS.18
In part, this concern arises from different routes of HIV transmission in the United States, including through intravenous drug users and men who have sex with men (MSM), which constitute a substantial proportion of HIV infections in the United States. While African Americans represent only 13% of the total population, they account for 48% of all HIV infections. 18
Rates of HIV in inner cities such as Washington, DC, approach levels seen in Africa, with 3% to 5% of the total adult population living with HIV, with 6.5% of African American males in Washington, DC, living with the virus.19
Heterosexual exposure is becoming the leading mode of HIV transmission, with 38% of incident cases among youth (ages 13-24 years) in Washington, DC.19
Additionally, in a retrospective study of 394 Baltimore, Maryland, STI clinic patients with known heterosexual HIV exposure, HIV infection was 22% among uncircumcised men compared with 10% in circumcised men (adjusted prevalence rate [PR], 0.49; 95% CI, 0.26-0.93).20
Thus, the results of the African trials appear to be relevant to heterosexuals at high risk of HIV infection in the United States.
Some have speculated that the findings of the adult male circumcision trials may not be applicable to neonatal circumcision. However, the large majority of the observational data are from individuals who were circumcised as infants. The remarkable consistency between the observational studies and the randomized controlled trials demonstrates that this concern is unfounded and further establishes the long-term protective effect of male circumcision.
Male circumcision and HIV protection among MSM have not been studied as well as heterosexual transmission. Several observational studies in MSM suggest that male circumcision is associated with decreased HIV infection, 21,22
while others found no protective effect.23
In a meta-analysis of 53 567 MSM, the odds of being infected with HIV were not significantly lower among circumcised compared with uncircumcised men (odds ratio [OR], 0.95; 95% CI, 0.81-1.11).24
However, a significant protective effect was found in MSM studies conducted prior to the availability of highly active antiretroviral treatment (OR, 0.47; 95% CI, 0.32-0.69).24
The protective effect of circumcision among MSM is complicated by both insertive and receptive sexual practice, and it is possible that circumcision only protects against insertive intercourse. This is supported by the Soweto Men’s Study of men who participate in exclusive insertive anal intercourse, which found that uncircumcised men have a higher risk of HIV infection than circumcised men (adjusted OR, 4.5; 95% CI, 3.1-6.7).25
Thus, studies that do not differentiate between these practices may be confounded. It is noteworthy, however, that in a recent HIV vaccine trial, circumcised MSM had a significantly lower risk (relative risk, 0.26) of HIV acquisition compared with uncircumcised MSM participants.26
Thus, further research is required to determine whether male circumcision can definitively reduce HIV acquisition among MSM.