Increasing evidence demonstrates that short-term conditional economic incentives may improve adherence to antiretroviral therapy (ART) for people living with HIV, thereby conferring individual health benefits and preventing transmission. However, few previous studies have assessed viral suppression, a biomarker of adherence and the ultimate goal of HIV “treatment as prevention” efforts. Moreover, questions remain around pathways of impact, best practices for real-world implementation, and durability of effects. For example, there is a lack of coherent evidence indicating whether such incentives mitigate food insecurity, an underlying barrier on the hypothesized pathway between economic incentives and ART adherence. Additionally, essential details for scaling up implementation remain largely unexplored, including optimal design and distribution aspects that can affect scalability. Finally, the short follow-up period for most prior studies inhibits understanding of any long-term harms or benefits of time-limited incentives. To address these gaps, this work studied the effects of cash and food incentives in two randomized trials of adults initiating ART in rural Tanzania. It evaluated outcomes including food insecurity, viral suppression, and long-term retention in care, and investigated the roles of incentive size and delivery mode.
Chapter 1 assessed effects of short-term cash and food incentives for HIV care on food security, nutrition, and livelihoods. This analysis used data from a 2013-2016 study of 800 food-insecure ART initiates at three HIV primary care clinics in Shinyanga region, Tanzania. Participants were randomized to receive usual HIV care (control group) or to additionally receive cash or food transfers for up to 6 consecutive months, conditional on timely attendance at scheduled clinic visits. The primary study results demonstrated that both cash and food incentives increased medication possession and retention in care at 6 and 12 months compared to the control group. The analysis herein found that food security, nutritional status, and work status improved over time in all groups, potentially due to the benefits of ART on physical health and the ability to work. Incentives further reduced severe food insecurity at 6 months relative to usual care but had no effects on these other measures at 6 or 12 months. These results suggest that alleviating severe short-term food insecurity via a modest income effect is one plausible pathway for incentives to bolster ART adherence. The lack of impact on other outcomes indicates that small incentives likely operate primarily via a price effect, lowering costs associated with clinic attendance. Moreover, the overall improvements in well-being after starting ART underscore the importance of strategies to support adherence both for ending the HIV epidemic and strengthening livelihoods.
Chapter 2 evaluated impacts of two different sized financial incentives for HIV care on viral suppression. A randomized trial was conducted at four health facilities in Shinyanga region, Tanzania (2018-2019), whereby 530 adult ART initiates were randomized to receive usual HIV care or to additionally receive a financial incentive for monthly clinic attendance in the amount of 10000 (US $4.50) or 22500 (US $10) Tanzanian Shillings for up to 6 months. Mobile health technology (mHealth) was used to implement biometric attendance monitoring linked to automated electronic payments. The study found that both incentive amounts improved viral suppression at 6 months, with a trend toward larger effects with increasing incentive size. As the first randomized trial to evaluate the impact of clinic-based financial incentives for treatment-seeking behavior on HIV viral suppression in a low- or middle- income country, these findings contribute critical evidence for understanding the promise of financial incentives to improve HIV treatment adherence.
Chapter 3 ascertained the long-term effects of time-limited incentives for HIV care. Individuals who had participated in the previous study of cash and food incentives in Tanzania were followed up after 3 years had elapsed since enrollment in the original trial. These former participants were located using gold standard tracing procedures including phone calls, home visits from community health workers, and triangulation with other facilities. Clinic attendance records obtained at follow-up were used to measure retention in care and mortality at 24 and 36 months. Contributing to the scientific gap regarding long-run incentive effects, the results showed no significant differences between study groups in retention or mortality, indicating neither lasting benefit nor eventual harm from short-term incentives.
Together, these findings contribute an improved understanding of the effectiveness and optimal implementation of conditional economic incentives to promote HIV treatment adherence. The short-term effects on food insecurity show that incentives may help stabilize vulnerable households at the time of ART initiation, thereby supporting improved adherence. Next, the viral suppression results definitively show that incentives have impact on a biological measure of ART adherence, and that these effects can be achieved using mobile health technology to deliver incentives. A trend toward increasing effectiveness with larger incentives was established, while even the smallest incentive tested resulted in significant improvement over the standard of care. Lastly, the long-term results found no eventual harm from incentives, while benefits gradually reduced over time. These findings demonstrate that economic incentives are a safe and effective strategy to promote adherence at the time of ART initiation, adding a major contribution to evidence-based approaches to ending the HIV epidemic.