Definition of the Prevention Area
Antiretroviral (ARV) drugs, used to improve the health of people living with HIV, have also been shown to reduce HIV transmission to HIV-negative people. By reducing viral load in the HIV-positive partner, ARV drugs have been shown to lower the risk of HIV transmission to the uninfected partner. Similarly, some recent studies of pre-exposure prophylaxis have suggested that ARV drugs may reduce transmission, even when taken by HIV-negative persons at risk for HIV infection. The topic of pre-exposure prophylaxis is covered in another Prevention Knowledge Base.
Summary of the Evidence
HIV circulates at high levels in blood, semen, vaginal fluids, and breast milk in HIV-positive people who are not taking ARV drugs. Effective ARV therapy (ART) lowers HIV levels in these fluids, often below the limit of detection of standard viral load assays. Antiretroviral drugs reduce HIV levels in pregnant and breastfeeding women enough to significantly lower the risk of mother-to-child transmission. Multiple observational studies have provided evidence that a lower viral load—and ART to lower one’s viral load—decrease the chance of HIV transmission. These data informed the development of several clinical trials to determine ARVs’ effect on HIV transmission at individual and population levels. One published trial, HIV Prevention Trials Network (HPTN) 052, reported the HIV transmission rates between serodiscordant partners randomized to have the HIV-positive partner start ART immediately or wait until his/her CD4 count fell below 250 cells/mm3. In this trial, authors reported a 96 percent reduction in the risk of HIV transmission that could be genetically traced to the index partner (approximately 18 percent of new infections came from outside the partnership; see Eshelman et al. 2011) among those who started treatment immediately. The effect was so strong that the trial’s data safety and monitoring board recommended that all couples in the study be offered early treatment initiation.
Core Programmatic Components
The expanded use of ART in persons living with HIV as a tool to reduce HIV incidence among uninfected individuals has exciting potential, because ARV drugs also have the benefit of reducing morbidity and mortality in persons diagnosed with HIV. However, despite the encouraging results reported by HPTN 052, additional research and debate on policy and community implications are needed to identify the best approaches to implementation. To truly maximize the prevention benefit from HIV treatment, programs must ensure that:
- People are tested for HIV and linked to care and treatment programs
- HIV-diagnosed individuals agree to start ART
- ARV drugs are available and affordable
- Patients started on ART are retained in care and remain adherent to treatment
- Patients on ART do not engage in more risky behavior as a result of starting treatment.
While there have been impressive strides in expanding access to HIV treatment worldwide, improving the tolerability and acceptability of ARV drugs, and supporting ongoing patient retention and adherence, a number of issues must be considered as additional data from ongoing trials become available:
- Who are the most appropriate target populations? Who should be prioritized if resources are limited?
- What are the best ways to educate health workers and target populations on the benefits of HIV treatment?
- As demand increases, how will we ensure uninterrupted stocks of ARV drugs?
- What messages should we convey to improve uptake of testing, linkage to care, and lifelong adherence to ART?
Current Status of Implementation Experience
Since their inception, HIV treatment programs have been contributing to HIV prevention. However, many treatment programs still prioritize treating people who have the lowest CD4 counts. As HIV viral load—and risk of transmission—is highest during acute infection and with lower CD4 counts, this is one strategy to maximize the prevention benefit of ART with limited resources. The additional prevention benefit from expanding ART to people living with HIV in discordant relationships and at higher CD4 counts is currently under study. Treatment-as-prevention programs are being evaluated in several ongoing trials around the world—most notably in Botswana, Malawi, Mozambique, South Africa, Tanzania, Uganda, the United States, and Zambia—either separately or as part of combination prevention packages. HPTN 065 in the United States is exploring the strategy in two cities: New York, NY (specifically, the Bronx), and Washington, DC. The HPTN 052 study trial sites in Brazil, India, Malawi, Thailand, the United States, and Zimbabwe are continuing to offer all study couples early initiation of treatment and will follow them until the planned end date of 2015.