Cost-Effectiveness Analyses of Adolescent- and Young-Adult-Focused HIV Interventions Incorporating HIV Transmission: a Scoping Review of Modeling Methods and Proposed Guidance.

Background: Adolescents and young adults (AYA) are disproportionately affected by human immunodeficiency virus (HIV) globally, with high-burden population subgroups differing across regions. Cost-effectiveness modeling analyses of AYA-focused HIV interventions have provided vital information to policy makers by projecting long-term health and economic impacts of interventions' effects on reduced HIV transmission. To provide a broad overview of available modeling approaches and identify gaps in methods reporting, we evaluated modeling methodologies used in AYA-focused cost-effectiveness analyses incorporating HIV transmission.

Methods: We searched PubMed, Embase, and Web of Science for peer-reviewed articles that were published January 2006 to August 2023 and described models that considered HIV transmission in estimating cost-effectiveness of AYA-focused HIV prevention interventions. We extracted selected study characteristics, transmission model properties, and methods to estimate long-term health and economic outcomes. We assessed study quality using published guidelines.

Results: Among 42 studies, 38% included individuals assigned male or female sex at birth, 19% included females only, and 43% included males only; 24% focused on AYA only; 88% were set in Africa; and 7% were restricted to certain population subgroups. The most common population subgroups examined were women who have transactional sex (24%) and men who have sex with men (17%). Most (88%) studied primary prevention interventions for people at risk of HIV; 29% examined secondary prevention interventions including treatment and testing. Most (98%) assessed incremental cost-effectiveness ratios (ICERs) were defined as incremental cost per incremental life year (either quality-adjusted or disability-adjusted), or cost per infection averted, or both. Of 24 different transmission models identified with distinct structures, 59% were dynamic. Of 20 studies that translated averted infections into long-term health benefit, 55% used their transmission models directly through assigning health utilities to modeled states. A total of 30 studies converted averted infections into long-term cost savings, among which, 73% used their transmission models directly by assigning costs to modeled states. Fewer than half captured age-specific sexual and care-engagement behaviors. Important gaps in quality included incomplete reporting of model validation and calibration results.

Conclusions: We identified heterogeneous modeling approaches in cost-effectiveness analyses of AYA-focused HIV interventions incorporating transmission. Reporting of key elements could be improved. We propose additional criteria that could clarify choices around modeling approaches and strengthen the reporting of model validation and calibration results.