Antiretroviral Therapy as an HIV Prevention Strategy


I. Definition of the Prevention Area

Antiretroviral (ARV) drugs, used to improve the health of people infected with HIV, have also been shown to reduce HIV transmission to HIV-negative people. By reducing viral load in the infected partner, ARVs 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 ARVs 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 brief.

II. Summary of the Evidence

HIV circulates at high levels in blood, semen, vaginal fluids, and breast milk in people with HIV who are not taking ARVs. Effective ARV therapy (ART) lowers HIV levels in these fluids, often below the limit of detection of standard viral load assays. Antiretrovirals 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 taking ART to lower one's viral load--decreases the chance of HIV transmission. These data informed the development of several recent clinical trials to determine the impact on HIV transmission that ARVs can have on both individual and population levels. One recently published trial, HIV Prevention Trials Network (HPTN) 052, reported the HIV transmission rates between serodiscordant partnerships randomized to have the HIV-positive partner start ART immediately or wait until their CD4 count fell below 250 cells/mm3. In this trial, authors report a 96 percent reduction in the risk of genetically linked (i.e., approximately 18 percent of new infections came from outside the partnership [see Eshelman et al. 2011]) HIV transmission 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.

III. Core Programmatic Components

The expanded use of ART in persons living with HIV as a tool to reduce HIV incidence has exciting potential, as ARVs 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 around 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:

1.   People are tested for HIV and successfully linked to care and treatment programs
2.   HIV-diagnosed individuals agree to start ART
3.   ARV drugs are available and affordable
4.   Patients started on ART are retained in care and remain adherent to treatment
5.   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, there still remains unmet need in each of these areas. A number of other issues must also be considered as additional data from ongoing trials become available:

IV. Current Status of Implementation Experience

HIV treatment programs have been contributing to HIV prevention efforts since their inception. However, many treatment programs still prioritize treating those with lowest CD4 counts first. 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, South Africa, Uganda, Malawi, Tanzania, Mozambique, Zambia, and the United States--either separately or as part of combination prevention packages. HPTN 065 in the United States is exploring the strategy in two cities: New York (specifically, the Bronx), NY, 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.

What we know

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Putting it into practice

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Tools and Curricula

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Debate Six: Treatment as Prevention

World Bank & U.S. Agency for International Development. (2012).

This report outlines the sixth in the Emerging Issues in Today's HIV Response debate series sponsored by the World Bank and the U.S. Agency for International Development. In November 2011, a panel of four renowned public health experts--two each assigned to argue for and against--addressed the proposition: countries should spend a majority of what is likely to be a flat or even declining HIV prevention budget on treatment as prevention. The topic was inspired by the stunning findings of the recent HIV Prevention Trial Network (HPTN) 052 clinical trial of serodiscordant couples showing that early treatment reduces the risk of HIV transmission to an uninfected partner by at least 96 percent. Among other arguments, the two panelists in favor said that because of the overwhelming evidence for the effectiveness of treatment as prevention, ethical principles require that this strategy be implemented quickly as part of comprehensive HIV prevention and care programming. The two panelists in opposition countered that, despite HPTN 052's powerful results, a blanket recommendation to launch treatment as prevention is premature, because there are still too many unanswered questions about its long-term effects in different populations. They also argued that each country's response to HIV should not be driven by a single programming imperative but instead reflect the specific characteristics and prevention needs of the local epidemic. More than 800 people worldwide registered to attend the debate either in person in Washington, via the Internet, or by video conferencing.

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The Impact of ART on HIV and TB: South African Centre for Epidemiological Modelling and Analysis

Williams, B. (2009).

This complex, technical presentation shows the formulae and models used for assessing the impact of ART on HIV and tuberculosis (TB). It includes models and studies looking at the following various outcomes: increases in TB with declines in CD4 cell counts, decreases in disease duration as incidence increased, reduction in TB when on ART, and predicted versus observed CD4 cell counts. The presentation ends with research needs, such as models that include age, gender, and better data to inform the assumptions.

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Informal Working Group Meeting: Modelling the Impact of ART on TB and HIV

WHO. (2009).

These notes from the informal working group meeting discussing modeling simulations provide a flavor of the presentations and discussion taking place among participants. As a result of the discussions, recommendations on moving forward were made for designers of trials to provide proof of concept, for considerations for developers of models, and for the WHO as a convening body.

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The Case for Expanding Access to Highly Active Antiretroviral Therapy to Curb the Growth of the HIV Epidemic

Montaner, J. S., Hogg, R., Wood, E., et al. The Lancet (2006), Vol. 368 No. 9543, pp. 531-6.

This commentary makes the case that the HIV pandemic presents "an exceptional threat to humanity" and that "similarly exceptional interventions" are needed to reverse the pandemic. Given that prevention efforts are only partially successful and underused, a vaccine is not on the horizon, and current treatment cannot eradicate infection, the authors argue that there is potential for HAART to help stem the HIV epidemic. The authors present a brief theoretical model of their approach.

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AVAC, Global Advocacy for HIV Prevention

The website offers the latest news on the past, present, or ongoing status of biomedical HIV prevention research studies. Readers can review summary tables from various HIV prevention clinical trails, search information on prevention trails, see what is new on the site this month, and review the user's guide for help in using the site. The site offers information about the following biomedical prevention trails: Microbicides, pre-exposure prophylaxis (PrEP), Treatment as Prevention, and Vaccines.

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View AVAC's HIV Prevention Research and Development Database (PxRD)