Over forty epidemiological studies have been conducted to investigate the relationship between circumcision and HIV infection. Reviews of these studies have reached differing conclusions about whether circumcision could be used as a prevention method against HIV.
Experimental evidence was needed to establish a causal relationship between lack of circumcision and HIV, so three randomized controlled trials were commissioned as a means to reduce the effect of any confounding factors. Trials took place in South Africa, Kenya and Uganda. All three trials were stopped early by their monitoring boards on ethical grounds, because those in the circumcised group had a lower rate of HIV contraction than the control group. The results showed that circumcision reduced vaginal-to-penile transmission of HIV by 60%, 53%, and 51%, respectively.
As a result of these findings, the WHO and the Joint United Nations Programme on HIV/AIDS (UNAIDS) stated that male circumcision is an efficacious intervention for HIV prevention but should be carried out by well trained medical professionals and under conditions of informed consent (parents consent for their infant boys). Both the WHO and CDC indicate that circumcision may not reduce HIV transmission from men to women, and that data is lacking for the transmission rate of men who engage in anal sex with a female partner. The joint WHO/UNAIDS recommendation also notes that circumcision only provides partial protection from HIV and should never replace known methods of HIV prevention.
Meta-analyses by Van Howe and Bosch et al. of observational studies had differing conclusions as to whether circumcision reduces infection of human papilloma virus. A recent prospective trial in Uganda randomized 3393 subjects to circumcision or a control group and found a significant reduction of HPV infection in the circumcision group. At 24 month follow-up, there was a 27.9% prevalence of high-risk HPV genotypes in the control group and only a 18.0% prevalence in the circumcision group (adjusted risk ratio, 0.65; 95% CI, 0.46 to 0.90; P=0.009). Another recent trial by Auvert et al. in Orange Farm, South Africa, randomized men to either a circumcision or control group. At the 21 month visit, the prevalence of high-risk HPV infection was lower in the circumcised men than the uncircumcised participants (14.8% and 22.3% respectively, a prevalence rate ratio of 0.66).
A meta-analysis of observational data from twenty-six studies found that circumcision was associated with lower rates of syphilis, chancroid and possibly genital herpes. A large randomized prospective trial in Uganda found a reduction in HSV-2 infection, but not syphilis infection, in the circumcision arm of the study.
A meta-analysis of 12 studies (one randomised controlled trial, four cohort studies and seven case-control studies) representing 402,908 children determined that circumcision was associated with a significantly reduced risk of urinary tract infection (UTI).
