Abstract
BACKGROUND: A more nuanced understanding of behavioural responses to incentives over time, particularly after they are removed, could guide more effective interventions. In this study, we build on the primary trial evaluation to explore the dynamic effectiveness of small, short-term monthly financial incentives on HIV care-seeking behaviours during and after incentive removal. METHODS: We conducted a 32-site cluster-randomised controlled trial (NCT04201353) among adult antiretroviral therapy (ART) initiates (<30 days) in four regions of Lake Zone, Tanzania. HIV care and treatment clinics were randomly assigned 1:1 to the intervention (up to 6 monthly cash transfers of 22 500 TZS each (~US$10), conditional on appointment attendance) or standard of care. Using time-to-event analysis, we assess the effect of incentives on three HIV-care seeking behaviours: missed appointment by >4 days, <90% ART adherence and interruption in treatment of >28 days. RESULTS: Among 1990 participants, we found large significant reductions in rate of missed appointments (hazard ratio (HR), 95% CI: 0.51, 0.39 to 0.68), <90% ART adherence (HR, 95% CI: 0.58, 0.41 to 0.83) and interruption in treatment (>28 days without ART) (HR, 95% CI: 0.54, 0.35 to 0.83) during the 6 months of incentives, but no effects after their removal. HRs by month reveal similar findings, with dramatic and consistent reductions in risk concentrated in months 2-6 that disappear in month 7, immediately after incentives are discontinued. CONCLUSIONS: These results highlight the value of short-term incentives for initiating new care-seeking behaviours and emphasise a need for innovative design choices, such as escalating rewards or incorporation of time- or context-based cues, that may help motivate sustained behaviour change after their removal. TRIAL REGISTRATION NUMBER: NCT04201353.