This will be a fairly regular bulletin, in which I will summarise and comment on the latest news and research about circumcision.
At present, the headlines are covering two studies in Africa that were stopped early because circumcision was shown to be effective in reducing the risk of HIV infection. Like last year's South African study, but unlike earlier research, they were randomised controlled trials.
The results, released on December 13, 2006, were striking. 2,784 men were involved in the Kenyan study, which found a 53% reduction in risk. 4,996 men were involved in the Ugandan study, which found a 48% reduction in risk.
The studies have not yet been published, but good sources include the National Institutes of Health release and their Q&A document.
The Cochrane Library contains an excellent systematic review of the literature as of April 9, 2003. It has not been updated to reflect the randomised controlled trials (RCTs) mentioned above, but 35 observational studies were reviewed. The authors concluded:
We found insufficient evidence to support an interventional effect of male circumcision on HIV acquisition in heterosexual men. The results from existing observational studies show a strong epidemiological association between male circumcision and prevention of HIV, especially among high-risk groups. However, observational studies are inherently limited by confounding which is unlikely to be fully adjusted for. In the light of forthcoming results from RCTs, the value of IPD analysis of the included studies is doubtful. The results of these trials will need to be carefully considered before circumcision is implemented as a public health intervention for prevention of sexually transmitted HIV.These RCTs are now available, and confirm the protective effect. Hopefully, the Cochrane Collaboration will soon update their review. In the meantime, the World Health Organisation plan to "review the detailed trial findings and will then define specific policy recommendations for expanding and/or promoting male circumcision."
How is it protective? Well, the US Center for Disease Control explain it so:
Compared to the dry external skin surface, the inner mucosa of the foreskin has less keratinization (deposition of fibrous protein), a higher density of target cells for HIV infection (Langerhans cells), and is more susceptible to HIV infection in laboratory studies . It has also been argued that the foreskin may have greater susceptibility to traumatic epithelial disruptions (tears) during intercourse, providing a portal of entry for pathogens including HIV . In addition, the micro-environment in the preputial sac between the unretracted foreskin and the glans penis may be conducive to viral survival . Finally, the higher rates of sexually transmitted genital ulcerative disease, such as syphilis, observed in uncircumcised men may also increase susceptibility to HIV infection .Although the CDC have not cited all work, other studies support the above.