Neonatal vs adult circumcision: health benefits

There’s currently a rather heated discussion going on in the Pit on the subject of circumcision, and one point that has been stated more than once by some rather excitable individuals is that the ‘benefits’ of circumcision (protection against HIV infection) only apply if it is done neonatally. Circumcision performed in adulthood supposedly provides no benefit.

Is this actually true? And if so, what would be the reason for it?

Citations to reputable research journals are preferable to typing in all caps, thanks.

There are a few sites out there that say adult circumcision could have the same effect as if it were done as a baby:

From CBC.CA

From Medpagetoday.com

Or you can just check out ol’ google