Circumcision: a surprising benefit from an unkind cut
David Margolis, for natap.org
Tom Quinn of Hopkins and the NIAID reviewed the maturing data that show that male circumcision confers protection against HIV infection. The biological basis for the protective effect of circumcision is not clear, but the foreskin is not keratinised and heavily enriched in dendritic cells, making it a potentially advantageous entry site for the virus. Quinn reported a number of epidemiological facts that suggested circumcision protects against HIV infection:
- The relative risk of HIV infection was 0.56 in circumcised men.
- The relative protective effect is even greater in men with high-risk demographics, in whom the relative risk in circumcised high-risk men for acquisition of HIV was only 0.29.
- Countries in which >80% of the men are circumcised have lower HIV prevalence than countries in which <20% of the men are circumcised.
- In a cohort of HIV sero-discordant partners in Rakai, none of 50 circumcised men acquired HIV, irregardless of their partners viral load.
- Kenyan truck drivers are 2.5-fold more likely to be HIV infected if uncircumcised
- In circumcised Indian men presenting to STD clinics, 88% did not acquire HIV despite the fact that their acquisition rate of HSV, syphilis and GC rates were the same as uncircumcised men This hypothesis has been preliminarily tested in a South African study in which sterile circumcision was provided to a cohort of at-risk men. A 75% reduction in HIV acquisition risk was reported, with 58 adverse events (3.8%) related to the procedure. The studys conclusions are limited, as follow-up is so far short-term, protection was incomplete, and it is unclear if these results could be generalised outside of southern Africa. Two other studies are expected to be reported in the summer of 2006.
Quinn suggested that as a public health measure safe circumcision should be made available now, and further data developed. In a model of the effect of circumcision, a 50% reduction in relative HIV acquisition risk would cut HIV incidence from 0.8 per 100 person years to 0.4 in women, in addition to the 50% protective effect in men. But if 30% of men believed that sex was now safe and stopped using condoms, the beneficial effect would be abrogated.
The procedure was estimated to cost $69 in Rakai, and therefore would cost 1000 to 3000$ per HIV case prevented. This cost is similar to that of nevirapine prophylaxis for pregnant mothers, in which the cost of an averted infection is estimated to be $2500. Quinn felt that overall circumcision could reduce HIV and STD transmission, reduce cervical cancer, balanitis, and penile cancer. He suggested that preparations be made to offer safe surgery and educate to maintain low-risk behavior.
Quinn T. Circumcision and HIV transmission: the cutting edge. Plenary lecture Wednesday 8 February, 13th CROI, 2006, Denver. Abstract 120. Webcast available on conference website.