RESUMEN
INTRODUCTION: We aimed to evaluate daily oral pre-exposure prophylaxis (PrEP) uptake, retention, and adherence and predictors of study non-attendance and low PrEP adherence in a Brazilian trans-specific 48-week study (PrEParadas). METHODS: We enrolled transgender women (TGW) engaging in high-risk sexual behaviours between August 2017 and December 2018. PrEP adherence was based on tenofovir diphosphate concentrations in dried blood spots (DBS). We used random effects logistic regression models and ordinal models to estimate the odds of having a missed visit and of low PrEP adherence, respectively. Multivariable models were adjusted for variables with p-value<0.10 in the univariate analysis. RESULTS: From the 271 eligible, 130 participants were enrolled in the study (PrEP uptake: 48%), out of which 111 (85.4%) were retained at 48 weeks. Multivariable model for study non-attendance included study visit, age, main sexual partner and stimulant use. The odds of missing a visit increased after the week 24. Participants aged 18-24 (adjusted odds ratio [aOR] = 8.76, 95% CI: 2.09-36.7) and 25-34 years (aOR = 6.79, 95% CI: 1.72-26.8) compared to TGW aged 35+ years had significantly higher odds of having a missed visit. The odds of a missed visit were higher among participants reporting stimulant use (aOR = 4.99, 95% CI: 1.37-18.1) compared to no stimulant use. DBS levels at week 48 showed that 42 (38.5%), 14 (12.8%) and 53 (48.6%) of 109 participants had low, moderate and high PrEP adherence. Multivariable model for low PrEP adherence included study visit, age, schooling, race/colour, housing, binge drinking, stimulant use, feminizing hormone therapy (FHT) use and received text message. Low PrEP adherence was significantly higher among participants with less years of schooling (aOR = 6.71, 95% CI: 1.30-34.5) and had a borderline association with Black colour/race (aOR = 6.72, 95% CI: 0.94-47.8). Participants using the FHT available at the site had decreased odds of low PrEP adherence (aOR = 0.38, 95% CI: 0.16-0.88). No participant seroconverted over the course of the study. CONCLUSIONS: Although high PrEP retention can be achieved in a gender-affirming setting, PrEP adherence may be an important challenge faced among TGW due to social disparities. The scale-up of prevention tools like PrEP will have to address systemic social determinants as these stand as important barriers for TGW's access to health services.