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How Much Can Early Treatment Reduce HIV Transmission Among Discordant Couples?

Treating the HIV positive partner in serodiscordant couples can decrease the risk of transmitting the virus, but the extent of the reduction will likely vary from country to country based on population size, HIV prevalence, and number of discordant couples, according to a mathematical model study described in the October 11, 2011, advance online edition of AIDS.

Wafaa El-Sadr from Columbia University, and Sally Blower and Brian Coburn from the UCLA Center for Biomedical Modeling developed mathematical models to predict the reduction in HIV incidence and the number of infections that could be prevented if HIV positive partners in mixed-status couples started antiretroviral therapy (ART) upon diagnosis.

As reported this summer, the HPTN 052 study showed that couples in which the positive partner started immediate ART had a 96% lower risk of HIV transmission compared with those who delayed treatment until their CD4 T-cell count fell below 250 cells/mm³.

In the present analysis, the investigators used demographic and epidemiological data from Ghana, Lesotho, Malawi, and Rwanda to establish parameters for the model, assuming ART was 96% effective at preventing transmission.

Results

• The models predicted that there would be a "fairly large" reduction in HIV incidence and a "substantial" number of infections prevented in Malawi.
• In Ghana, however, while a large number of infections would be prevented, this would only result in a small reduction in incidence.
• In Lesotho and Rwanda, the predicted number of infections prevented would be similar -- and low -- but the reduction in incidence would be substantially greater in Lesotho than in Rwanda.
• The higher the proportion of people in stable partnerships -- whether seroconcordant or discordant -- the greater the impact of early treatment on a local epidemic.

"The effectiveness of a discordant couples intervention in reducing incidence will vary among countries due to differences in HIV prevalence and the percentage of couples that are discordant," the researchers concluded.

"The number of infections prevented within a country, as a result of an intervention, will depend upon a complex interaction among three factors: population size, HIV prevalence, and degree of discordancy," they continued. "Our model provides a quantitative framework for identifying countries most likely to benefit from treating discordant couples to prevent transmission."

"The findings from the modeling study provide insights into what to expect at a country level of expanding such a prevention strategy," El-Sadr said in a press release issued by Columbia's Mailman School of Public Health. "Getting information to countries with regards to what they can expect from scale up of treatment for discordant couples on their epidemics is critical to their decision making." 

"Our findings are very important as they show the intervention may be very successful in certain countries but not in others," added Blower. "This means we can use our model to identify which specific countries should begin to rollout this intervention."

Investigator affiliations: ICAP, Mailman School of Public Health, Columbia University, New York, NY; Center for Biomedical Modeling, University of California at Los Angeles David Geffen School of Medicine and Semel Institute of Neuroscience and Human Behavior, Los Angeles, CA.

11/1/11

Reference

WM El-Sadr, BJ Coburn, and SM Blower. Modeling the impact on the HIV epidemic of treating discordant couples with antiretrovirals to prevent transmission. AIDS. October 11, 2011 (Epub ahead of print).

Other Source

Columbia University’s Mailman School of Public Health. Expanding HIV Treatment for Discordant Couples Could Significantly Reduce the Global HIV Epidemic. Press release. October 21, 2011.