Beyond the jab: Modeling HIV vaccine acceptance in sexual and gender minorities with behavioral economic demand

Abstract

This study was an investigation of the utility of behavioral economic demand curves (quantitative models showing how consumption changes with price) in assessing acceptance of hypothetical HIV vaccines among sexual and gender minorities (SGMs). Two experiments used simulated purchase tasks (hypothetical scenarios measuring purchasing decisions). SGMs were recruited through Reddit and LGBTQ+ community organizations across the United States. In Experiment 1, participants were randomly assigned to nine instructional sets combining varying vaccine administration modes (oral, mucosal, or subcutaneous) with different dosage schedules (one dose, two doses, or one dose annually). Experiment 2 examined how bundling HIV vaccines with one of nine health commodities affected demand. Participants also responded to questions assessing demographics, HIV risk behaviors, experiences of racial discrimination, and trust in institutions. The results demonstrated that the exponentiated demand equation effectively modeled vaccine acceptance across conditions (median R² = 0.92). Contrary to expectations, vaccine characteristics had a minimal influence on demand (Q₀: R² = 0.007; log α: R² = 0.001). Instead, individual factors significantly influenced demand intensity (consumption when price = 0; Q₀) and price sensitivity (sensitivity of consumption to increasing price; α). Significant predictors of Q₀ included injection drug use history, experiences of racial discrimination, and trust in science. Low household income was the strongest predictor of log α. Bundling HIV vaccines with other health commodities showed subtle effects on acceptance, with condoms and dental examinations significantly differing from the reference category. These findings suggest that behavioral economic approaches can inform policy decisions about pricing, bundling strategies and targeted interventions to maximize HIV vaccine uptake among SGMs who face disproportionate HIV risk without requiring exposure to non-market-ready vaccines.