A new Chinese study conducted among heterosexual couples of mixed HIV status found that antiretroviral (ARV) therapy does not substantially reduce the risk of HIV transmission in a real-world setting. The study, published October 1 in the Journal of Acquired Immune Deficiency Syndromes, and reported by aidsmap, suggests that more data might be needed before rushing to roll out HIV treatment-as-prevention programs around the globe.

Treatment-as-prevention rests on a fairly well-established theory that when ARV therapy reduces an HIV-positive person’s viral load, he or she will be less likely to transmit the virus to sex partners. While this has been noted for nearly a decade, the strategy has received increasing attention in light of recent studies showing a reduction in HIV transmission in both San Francisco and Vancouver, two cities where an increasing number of HIV-positive people have received ARV therapy and the average community viral loads have dropped substantially.

To test this theory further, researchers looked at HIV transmission rates among 1,927 mostly monogamous couples in the Henan province of China, where one of the partners had HIV and the other did not. Many people in this province became infected from tainted equipment used for blood donations.

Surprisingly, the researchers found that there was no statistically meaningful difference in the rate of transmission in the couples whose HIV-positive partner was on ARV therapy (3 percent transmission) compared with couples where the HIV-partner was not on treatment (5 percent transmission).

The study’s authors acknowledge that poor adherence could have contributed to the failure to find that ARV therapy reduced transmission risk. Nevertheless, aidsmap reports that Myron Cohen, MD, from the University of North Carolina in Chapel Hill said in an accompanying editorial that the study results “demand a giant pause.”

“Will ART suppress transmission of HIV under ‘real life’ conditions?” he asks. “[I]t seems wise to try and answer this question before we fully deploy a ‘Test and Treat strategy,’ expecting to detect a benefit to the general population.”