A large Chinese study claims that treating HIV is much less effective at preventing transmission of the virus among serodiscordant couples than previously believed, MedPage Today reports. The study, published in the online edition of the Lancet, claims that treatment only reduced transmission rates by 26 percent. This challenges the HPTN 052 trial of 2011, which found that antiretroviral (ARV) treatment reduced transmission rates by 96 percent.

Both the HPTN 052 trial and the Chinese study looked at heterosexual couples, but the Chinese study looked at serodiscordant relationships outside the confines of a tightly controlled research study.

Using records from Chinese epidemiology and treatment databases covering 2003 through 2011, Yiming Shao, MD, of the Chinese Center for Disease Control and Prevention in Beijing and colleagues examined data on 38,862 serodiscordant couples, including 101,295 person-years of follow-up for the HIV-negative partners. They found that, among the 14,805 couples in which the HIV-positive partner was not on ARVs, the rate of transmission was 2.6 per 100 person years; while among the 24,057 couples in which the HIV-positive partner was on treatment, the rate of transmission was 1.3 per 100 person-years.

Researchers could only state with certainty that the 26 percent reduction in the rate of transmission was significant in the first year of treatment; the reduction lost significance in subsequent years in their statistical analysis. They wrote that more research is needed to understand whether the benefits of treatment as prevention endure over time, and to deduce how data from studies like this can be applied to the real world.

How these findings compare with those of HPTN 052, and how they might affect the treatment as prevention strategy will be topics of considerable importance to the HIV community. Look to POZ and AIDSmeds for further developments.

To read the MedPage Today report, click here.

To read the Lancet study abstract, click here.