Risk Behaviors and Risk Factors for HIV Infection among Participants in the Bangkok Tenofovir Study, an HIV Pre-Exposure Prophylaxis Trial among People Who Inject Drugs

an HIV Pre-Exposure Prophylaxis Trial among People Who Inject Drugs. PLoS ONE 9(3): e92809. doi:10.1371/journal.pone.0092809 Risk Behaviors and Risk Factors for HIV Infection among Participants in the Bangkok Tenofovir Study, an HIV Pre- Exposure Prophylaxis Trial among People Who Inject Drugs Michael Martin 0 Suphak Vanichseni 0 Pravan Suntharasamai 0 Udomsak Sangkum 0 Philip A. Mock 0 Manoj Leethochawalit 0 Sithisat Chiamwongpaet 0 Roman J. Gvetadze 0 Somyot Kittimunkong 0 Marcel E. Curlin 0 Dararat Worrajittanon 0 Janet M. McNicholl 0 Lynn A. Paxton 0 Kachit Choopanya 0 for the Bangkok Tenofovir Study Group " 0 Omar Sued, Fundacion Huesped, Argentina 0 1 Thailand MOPH - U.S. CDC Collaboration, Nonthaburi, Thailand, 2 Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America, 3 Bangkok Tenofovir Study Group , Bangkok, Thailand, 4 Bangkok Metropolitan Administration, Bangkok , Thailand , 5 Thailand Ministry of Public Health , Nonthaburi , Thailand Introduction: HIV spread rapidly among people who inject drugs in Bangkok in the late 1980s. In recent years, changes in drug use and HIV-associated risk behaviors have been reported. We examined data from the Bangkok Tenofovir Study, an HIV pre-exposure prophylaxis trial conducted among people who inject drugs, to assess participant risk behavior and drug use, and to identify risk factors for HIV infection. Methods: The Bangkok Tenofovir Study was a randomized, double-blind, placebo-controlled trial. HIV status was assessed monthly and risk behavior every 3 months. We used generalized estimating equations logistic regression to model trends of injecting, needle sharing, drugs injected, incarceration, and sexual activity reported at follow-up visits; and proportional hazards models to evaluate demographic characteristics, sexual activities, incarceration, drug injection practices, and drugs injected during follow-up as predictors of HIV infection. Results: The proportion of participants injecting drugs, sharing needles, and reporting sex with more than one partner declined during follow-up (p,0.001). Among participants who reported injecting at enrollment, 801 (53.2%) injected methamphetamine, 559 (37.1%) midazolam, and 527 (35.0%) heroin. In multivariable analysis, young age (i.e., 20-29 years) (p = 0.02), sharing needles (p,0.001), and incarceration in prison (p = 0.002) were associated with incident HIV infection. Participants reporting sex with an opposite sex partner, live-in partner, casual partner, or men reporting sex with male partners were not at a significantly higher risk of HIV infection compared to those who did not report these behaviors. Conclusion: Reports of HIV-associated risk behavior declined significantly during the trial. Young age, needle sharing, and incarceration were independently associated with HIV infection. Sexual activity was not associated with HIV infection, suggesting that the reduction in HIV incidence among participants taking daily oral tenofovir compared to those taking placebo was due to a decrease in parenteral HIV transmission. - Competing Interests: The authors have declared that no competing interests exist. Introduction HIV spread rapidly among people who inject drugs (PWID) in Bangkok in the late 1980s [1] and HIV prevalence has remained high, ranging from 30% to 50% through 2009, the highest among risk populations surveyed [2]. During 20052012, we conducted the Bangkok Tenofovir Study (BTS), a randomized, double-blind, placebo-controlled trial, that showed that daily prophylaxis with tenofovir disoproxil fumarate (tenofovir) could reduce the risk of HIV infection among PWID [3,4]. The study provided an opportunity to determine whether trial participation would lead to increased risk behavior, to assess drug use, and to examine the relationship between injection practices, sexual activities, and incident HIV infection. Risk factor analysis also helps interpret BTS results: if participants were at risk of HIV infection because of drug injection practices, the efficacy result suggests that tenofovir reduces parenteral HIV transmission; if, on the other hand, HIV infection was primarily related to sexual exposure, the efficacy result lends support to trials showing pre-exposure prophylaxis can reduce sexual transmission [5,6,7], but the impact on parenteral transmission remains unclear. In this manuscript, we describe HIV-associated risk behaviors and drug use reported by participants, and examine risk behaviors and drugs injected to determine predictors of HIV infection. Descriptions of community engagement, enrollment, and safety and efficacy results have been published [3,4]. Ethical Review Committees of the Bangkok Metropolitan Administration (BMA) and the Thailand Ministry of Public Health and the U.S. Centers for Disease Control and Prevention Institutional Review Board approved the study protocol and consent forms. The study was conducted in 17 BMA drug-treatment clinics according to the principles expressed in the Declaration of Helsinki. HIV-uninfected individuals aged 20 to 60 years who reported injecting drugs during the previous year were candidates for the study. Volunteers meeting all eligibility criteria could enroll after providing written informed consent. A total of 2413 people enrolled and were randomly assigned in a 1:1 ratio to receive daily oral tenofovir 300 mg or placebo. At enrollment and monthly (28 days) visits, individualized riskreduction counseling was provided and oral fluid was tested for HIV antibodies (OraSure Technologies Inc., Bethlehem, USA). Newly infected individuals were referred for care according to national guidelines [8]. Risk behavior was assessed at enrollment, 3-monthly, and when oral fluid HIV test were reactive using an audio computer-assisted self-interview (ACASI). When a participant was incarcerated, staff contacted prison authorities to arrange a study visit. Visits were not conducted in police cells (i.e., jails) because of the unpredictable occurrence and relatively short duration of incarceration. Thai law prohibits the distribution of needles to inject illicit drugs and needles were not provided to participants; however, sterile needles are available without a prescription at low cost (510 baht/0.120.25 US dollars) in pharmacies in Bangkok. Generalized estimating equations logistic regression [9] was used to model trends of injecting, sharing, incarceration, and sexual activity. HIV incidence and exact 95% Poisson confidence intervals (CI) were calculated per 1000 person-years of HIVnegative observation. We used proportional hazards models [10] to evaluate baseline demographic characteristics; and, incarceration, drug injection, and sexual activity reported the visit of the first positive HIV test as predictors of HIV infection, controlling for treatment group in all models. Variables associated with HIV infection in bivariate analysis (p,0.1) were evaluated in a multivariable model. We (...truncated)