Which Intervention Synergies Maximize AGYW's HIV Outcomes? A Classification and Regression Tree Analysis of Layered HIV Prevention Programming.

INTRODUCTION:Intersecting behavioral, social, and structural factors increase adolescent girls' (AG) and young women's (YW) HIV vulnerability. Yet, understanding of optimal intervention synergies remains limited. We identified intervention combinations that statistically maximized reductions in AGYW's HIV-related risk. METHODS:Using data collected in 2018 with Zambian AG (n = 487, aged 15-19 years) and YW (n = 505, aged 20-25 years) after 12-14 months exposure to Determined, Resilient, Empowered, AIDS-free, Mentored, and Safe (multisectoral HIV program), we used classification and regression trees to explore relationships between interventions (safe space/social asset building [SAB] and provision of/linkage to youth-friendly health services [YFHS], education social protection [Educ], economic social protection [Econ]) and HIV-related outcomes (HIV testing, consistent condom use, transactional sex, and sexual violence experience from partners and nonpartners). RESULTS:Overall, 59.9% completed SAB and 81.5%, 35.4%, and 29.6% received YHFS, Educ, and Econ, respectively. For AG, HIV testing improved (from 73% to 83%) with exposure to all interventions, condom use improved with Econ (from 33% to 46%), transactional sex reduced with SAB + Educ, and sexual violence from partners and nonpartners reduced with Educ and SAB, respectively. For YW, HIV testing increased with Educ (from 77% to 91%), condom use increased with SAB + YFHS (from 36% to 52%), transactional sex reduced with combinations of all interventions, and sexual violence from partners reduced with YFHS and from nonpartners with SAB + Econ. CONCLUSIONS:Tailored interventions might be more effective than uniform combination intervention packages in reducing AGYW's HIV risk. AG benefitted most from SAB and/or Educ while YFHS, Educ, and/or SAB reduced YW's HIV-related risk. Educational and asset-building interventions could have the greatest impact on AGYW's HIV risk.