New Scientist reported back in August that circumcision could protect men against HIV. The full report went out in October, which (as usual for interesting articles) is behind a subscription wall. However, Nature Medicine has also covered the story and made it publicly accessible.
As pointed out in the article, the results of one study are by no means proof, but current thinking seems to lean towards the belief that there is a beneficial effect. This to me is a bit of a double-edged sword. Anything that reduces the infection rate is worth doing, but the only sureties are physical barriers. If people get into the mindset that circumcision will make them immune to infection, then they are far less likely to use condoms – with the possible result that incidences of other STIs will start to rise.
The study authors have the right idea when they talk about using this alongside other preventative measures. Not unlike using contraceptive pills as well as condoms to prevent pregnancy, this is something where one might like to make assurance double sure.