Factors influencing pre-exposure prophylaxis adherence among female sex workers in Kinshasa, Democratic Republic of the Congo: a prospective cohort study

BACKGROUND: Female sex workers (FSWs) in the Democratic Republic of the Congo (DRC) bear a disproportionately high burden of HIV infection. Daily oral pre-exposure prophylaxis (PrEP) is an effective HIV prevention strategy, but its public health impact depends on sustained adherence. Evidence of PrEP adherence among FSWs in the DRC remains limited. This study assessed PrEP adherence over time and identified factors associated with adherence among FSWs in Kinshasa. METHODS: We conducted a 6-month prospective cohort study among 120 FSWs receiving PrEP at four client-friendly healthcare centers in Kinshasa in 2024, hereafter referred to as Clinic A, Clinic B, Clinic C, and Clinic D. Adherence was assessed using self-reported missed doses over the previous seven days and pill count. Retention in care was documented at months 3 and 6. Multivariable logistic regression guided by a directed acyclic graph (DAG) was used to identify factors associated with adherence at inclusion, month 3, and month 6. RESULTS: The median age of participants was 28 years (interquartile range [IQR]: 24-37). Based on pill count, adherence increased from 80.0% at inclusion to 93.6% at month 3 and 95.1% at month 6, whereas self-reported adherence declined over time. In DAG-informed models, clinic site was significantly associated with adherence at baseline. Compared with Clinic A, participants attending Clinic B (adjusted odds ratio [aOR] = 5.7; 95% confidence interval [CI]: 1.4-22.3) and Clinic C (aOR = 11.4; 95% CI: 2.1-61.1) were more likely to be adherent. No independent predictors were identified at later follow-up points. Retention in care was 92% at month 3 and 84% at month 6. CONCLUSION: PrEP adherence among FSWs in Kinshasa was high and improved over time when measured objectively. Baseline site-level differences underscore the importance of contextual and programmatic factors in supporting adherence. These findings provide evidence to inform the optimization and scale-up of PrEP delivery models for key populations in the DRC and similar settings.