They have only never "proven " HIV causes AIDS in the same way one can not "prove" that smoking increases the risk of cancer or that jumping off a thirteen story building is fatal.Technically nothing can be proven. Still, best advice, don't jump off buildings, don't contract HIV. Don't think that because a sexual partner is circumcised, one is less likely to catch it. It would almost be a funny idea.....if it were not so scary that it might catch on.