Study findings provide conclusive evidence that the risk of HIV transmission through anal sex when HIV viral load is suppressed is effectively zero.Among the 782 serodifferent gay couples followed for almost 1600 eligible couple-years of follow-up, which included more than 76 000 reports of condomless sex, zero cases of within-couple HIV transmission were found. In the absence of ART, on the basis of the frequency and type of sex, for receptive condomless anal sex acts alone approximately 472 transmissions would have been expected. The results give equivalence of evidence for gay men as for heterosexual couples and indicate that the risk of HIV transmission when HIV viral load is suppressed is effectively zero for both anal and vaginal sex.
