Durability of effects from short-term economic incentives for clinic attendance among HIV positive adults in Tanzania: long-term follow-up of a randomised controlled trial

INTRODUCTION: Conditional economic incentives are shown to promote medication adherence across a range of health conditions and settings; however, any long-term harms or benefits from these time-limited interventions remain largely unevaluated. We assessed 2–3 years outcomes from a 6-month incentive programme in Tanzania that originally improved short-term retention in HIV care and medication possession. METHODS: We traced former participants in a 2013–2016 trial, which randomised 800 food-insecure adults starting HIV treatment at three clinics to receive either usual care (control) or up to 6 months of cash or food transfers (~US$11/month) contingent on timely attendance at monthly clinic appointments. The primary intention-to-treat analysis estimated 24-month and 36-month marginal risk differences (RD) between incentive and control groups for retention in care and all-cause mortality, using multiple imputation for a minority of missing outcomes. We also estimated mortality HRs from time-stratified Cox regression. RESULTS: From 3 March 2018 to 19 September 2019, we determined 36-month retention and mortality statuses for 737 (92%) and 700 (88%) participants, respectively. Overall, approximately 660 (83%) participants were in care at 36 months while 43 (5%) had died. There were no differences between groups in retention at 24 months (86.5% intervention vs 84.4% control, RD 2.1, 95% CI −5.2 to 9.3) or 36 months (83.3% vs 77.8%, RD 5.6, –2.7 to 13.8), nor in mortality at either time point. The intervention group had a lower rate of death during the first 18 months (HR 0.27, 95% CI 0.10 to 0.74); mortality was similar thereafter (HR 1.13, 95% CI 0.33 to 3.79). CONCLUSION: These findings confirm that incentives are a safe and effective tool to promote short-term adherence and potentially avert early deaths at the critical time of HIV treatment initiation. Complementary strategies are recommended to sustain lifelong retention in HIV care. TRIAL REGISTRATION NUMBER: NCT01957917