Sexual risk reduction in a cohort of injecting drug users in Bangkok, Thailand

Objective: Interventions to reduce sexual risk behavior among injecting drug users (IDUs) have generally had very modest effects, but almost all such interventions have been conducted within short time frames. This study assessed whether long-term participation in interventions to reduce sexual risk behavior was associated with reduced sexual risk behavior. Methods: A total of 806 IDUs participated in the Bangkok HIV Vaccine Trial Preparatory Cohort Study from 1995-1998 and remained in the study for at least 4 follow-up visits (approximately 16 months). Participants received HIV counseling and testing every 4 months and free condoms were provided. Structured interviews including questions on sexual behavior were administered every 4 months. Results: Approximately 40% of participants reported engaging in unprotected sex (vaginal intercourse without always using a condom) with a regular partner at each study visit, without any decline over time in this behavior. There were declines in the proportions of participants reporting unprotected sex with casual partners and with paid partners (men only) over time, but the declines were confined to the early period of the study. Unprotected sex with casual partners was associated with amphetamine use. Condom use increased substantially among participants who seroconverted for HIV during the study. Conclusions: Interventions to reduce sexual risk behavior among HIV-seronegative IDUs over extended periods were no more likely to be effective than shorter interventions. New programs are needed to reduce sexual risk behavior among amphetamine users and among IDUs who are currently seronegative but are engaging in injection risk behaviors and in unprotected sex with regular partners.