The results of observational studies have suggested that male circumcision reduces the risk of HIV infection, but until now there have been no randomized controlled intervention trials to test that theory, Dr. Bertran Auvert and colleagues note in their report, published in the November issue of PLoS Medicine.

Dr. Auvert, from Hopital Ambroise-Pare in Boulogne, France, and associates randomly assigned 1,546 uncircumcised, HIV-negative men ages 18 to 24 years residing in South Africa to circumcision and 1,582 to a wait control group. Those who underwent circumcision were instructed to abstain from sex for 6 weeks after the procedure.

During 21 months of follow-up, there were 20 incident cases of HIV infection in the intervention group and 49 in the control group (0.85 versus 2.1 per 100 person-years, p = 0.00059).

In the per-protocol analysis, the incidence rate ratio was 0.24.

The authors observed that those in the intervention group had more sexual contacts between month 4 and month 12, and between month 13 and month 21. Therefore, they note, "the protective effect of the intervention is not attributable to the change of reported behavior associated with the intervention."

Possible mechanisms for the protective effect include "keratinization of the glans when not protected by the foreskin, short drying after sexual contact, reducing the life expectancy of HIV on the penis after sexual contact with an HIV-positive partner, reduction of the total surface of the skin of the penis, and reduction of target cells, which are numerous on the foreskin."

While Dr. Auvert's group recommends male circumcision for reducing the risk of HIV infection in areas with high prevalence of the disease, they also caution that, "if perceived as full protection, (circumcision) could lead to reduction of protection of men who, for example, decrease their condom use or otherwise engage in riskier behavior."

PLoS Medicine 2005;2:e298

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