P15-10. Preventive HIV vaccine acceptability and behavioral risk compensation among high-risk men who have sex with men and transgenders in Thailand

Background

Thailand, site of numerous HIV chemoprophylaxis trials and the world's only ongoing phase-3 HIV vaccine trial, may be an early adopter of HIV vaccines. We assessed acceptability of preventive HIV vaccines and behavioral risk compensation among individuals from high-risk communities likely to be targeted for initial vaccine roll-out.

Methods

We developed a structured questionnaire based on our formative qualitative research (n = 30) among vulnerable community stakeholders, HIV physicians and HIV prevention experts in Thailand. The 30-minute questionnaire was programmed on laptop computers in Thai and administered by trained interviewers. Participants were recruited using venue-based sampling from sex venues and community-based organizations serving men who have sex with men (MSM), male sex workers and transgenders in Bangkok and Chiang Mai. We assessed HIV vaccine acceptability using conjoint analysis and a fractional factorial experimental design, and risk behavior intentions in response to HIV vaccine uptake.

Results

Participants (n = 260) were MSM (84.2%) and transgenders (15.8%); mean age = 26.7 (SD = 5.6) years. Most (58.1%) engaged in paid sex; 20.0% reported STI diagnosis (past year); with an average of 11.3 male partners (past 3 months). HIV vaccine acceptability ranged from 73.8 (SD = 29.6) to 31.9 (SD = 33.6) on a 100-point scale; mean = 58.5 (SD = 17.3). Vaccine-induced seropositivity (VISP) had the greatest impact on acceptability (18.5; p < 0.001), followed by efficacy (15.7; p < 0.001), side effects (9.4; p < 0.001), duration (5.0; p < 0.001), out-of-pocket cost (3.6; p = 0.005) and social saturation (i.e., percentage of the population already vaccinated; 2.5; p = 0.02). Over one-third (34.6%) reported intentions to increase sexual risk behaviors in response to HIV vaccine uptake.

Conclusion

Findings support the development of interventions to mitigate the impact of VISP, increase acceptability of partially efficacious vaccines and foster understanding about possible side effects, which may facilitate HIV vaccine uptake among high-risk MSM and transgenders in Thailand. Behavioral interventions to decrease risk compensation will be a crucial component of combination prevention.