Risk Factors for HIV Seroconversion in a High Incidence Cohort of Men Who Have Sex with Men and Transgender Women in Bangkok, Thailand

Abstract

Background: In order to assess feasibility for future HIV prevention trials, we measured HIV incidence, retention, and assessed risk factors for seroconversion among men who have sex with men (MSM) and transgender women (TGW) in Bangkok, Thailand between 2017-2019. Methods: We conducted an 18-month prospective cohort study of HIV-uninfected Thai cisgender men and transgender women who reported sex with men in the past six months. HIV and syphilis testing and computer-based behavioral questionnaires were administered at each visit. We utilized Poisson regression to calculate HIV incidence rates. A survival random forest model identified the most predictive risk factors for HIV seroconversion and then used in a survival regression tree model to elucidate hazard ratios for individuals with groups of selected risk factors. Cox proportional hazards (PH) regression evaluated the strength of association between individual covariates and risk of seroconversion. Findings: From April 2017-October 2019, 1,184 participants were screened, 167 were found ineligible, and 1,017 enrolled. Over the 18-month study, visit retention was 93·4% (95% CI 91·6%-94·8%) and HIV incidence was 3·73 per 100 person-years (95% CI 2·79-5·87). Utilizing survival regression tree modeling, those who were 18-20 years of age, reported sexual attraction to mostly or only men, and had five or more lifetime sexual partners were 4·9 times more likely to seroconvert compared to other cohort participants. Factors associated with HIV incidence utilizing Cox PH regression included sexual attraction to mostly or only men (adjusted hazard ratio (aHR) 14·9 (95% CI 20·1-107·9), younger age (18-19 years, aHR 10·88 (95% CI 4·12-28·7), five or greater lifetime sexual partners (aHR 2·0, 95%CI 1·1-3·6), inconsistent condom use with casual partners (aHR 2·43, 95% CI 1·3-4·5), and prior HIV testing (adjusted HR 2·0, 95% CI 1·1-3·5). Interpretation: HIV incidence remains high among Bangkok-based MSM and TGW. These key populations have high retention and are ideal candidates for efficacy evaluation of future prevention strategies. Funding Statement: This work was supported by the US Army Medical Research and Materiel Command (Military Infectious Diseases Research Program) (cooperative agreements W81XWH-11-2-0174 and W81XWH-07-2-0067 with the Henry M. Jackson Foundation for the Advancement of Military Medicine), the US Army Medical Materiel Development Activity, and the National Institute of Allergy and Infectious Disease (interagency agreement Y1-AI-2642-12 with the US Army Medical Research and Materiel Command) and the Division of AIDS Interagency Agreements (DAIDS IAA Y1-AI-2642-16). Declaration of Interests: T.C. reports grants from U.S. Army, grants from NIH, M.R. and S.V. reports grants from US Army Medical Research and Materiel Command with Henry M. Jackson Foundation for the Advancement of Military Medicine, during the conduct of the study. All other authors report no potential conflicts. Ethics Approval Statement: The study was reviewed and approved by the institutional review boards at Walter Reed Army Institute of Research (WRAIR), Faculty of Tropical Medicine at Mahidol University, and the Royal Thai Army. All participants provided written informed consent prior to enrollment.