“We carried her in a wheelbarrow to the clinic”: process evaluation of the AMETHIST intervention combining microplanning with self-help groups to improve HIV prevention and treatment among female sex workers in Zimbabwe

The Adapted Microplanning to Eliminate Transmission of HIV in Sex Transactions (AMETHIST) randomised controlled trial tested a combination of microplanning (peer-led risk-differentiated support) and self-help groups (SHGs) to reduce the proportion of female sex workers (FSW) at risk of acquiring or transmitting HIV infection in Zimbabwe. The trial found overall high levels of FSW engagement with treatment which further improved in intervention sites. HIV prevention uptake, however, was low and not affected by AMETHIST. We conducted a mixed methods process evaluation to assess implementation, explore FSW perceptions, and understand the trial’s outcomes. We integrated routine programme statistics, qualitative data, and an endline respondent driven sampling survey among 4444 FSW to consider fidelity of implementation, feasibility of delivery, and acceptability. We also examined whether the intervention triggered changes hypothesised in its programme theory. Microplanning was successfully introduced, with peers effectively providing risk-differentiated support. Early difficulties related to mapping sex work “hotspots,”, maintaining contact with mobile FSW, and some resistance to regular risk assessments, but double the number of new FSW registered at intervention clinics compared to comparison sites (8443 v 3824), and significantly more HIV tests were performed (11882 vs. 6808). SARS-COV2 disrupted the intervention, particularly SHG. Fewer groups were established than planned, and lockdowns prevented group members meeting in person and participating in collective activities. Nonetheless, 30 of 65 established SHG remained active after two years, and more SHG members registered with clinics than those reached by microplanning alone (82 cv 76% p,0.001). Increased service use did not increase effective prevention. Over 80% FSW reported condomless sex and PrEP adherence was insufficient to achieve protection. Qualitative data show FSW prefer to “wait” until HIV seroconversion before taking daily medication. They feared conflation of ART with PrEP and resulting stigma. Concerns about side effects and immediate financial priorities undermined perceived future benefits of PrEP and condoms. Strengthening HIV prevention should consider how to improve FSW’s hope and agency alongside reducing stigma and supporting collective rights and action. The Pan African Clinical Trials Registry registered the trial 2nd July 2020 (PACTR202007818077777) which was after randomisation but before any research data were collected.