Longitudinal Patterns of Adherence to Oral HIV Pre-Exposure Prophylaxis Among At-Risk Women in Tanga, Tanzania: A Convergent Analysis of Influencing Factors and Optimization Strategies

There is scarcity of evidence on the changes over time of adherence to oral HIV pre-exposure prophylaxis (PrEP) among female sex workers. Therefore, we assessed the changes of adherence to PrEP over 12 months and influencing factors for suboptimal adherence and explored strategies to optimize adherence to oral PrEP among female sex workers in Tanzania. Convergence analysis was conducted involving 313 respondent driven sampled participants in the city of Tanga. Adherence was assessed at months 1, 6, and 12. In month 12 we conducted 26 in-depth interviews in parallel with quantitative interviews. A modified Poisson regression and thematic analysis was conducted for quantitative and qualitative data respectively. The prevalence of suboptimal adherence at month 1 was 19.5% (95% CI 14.1-26.3), with a significant increase to 91.8% (95% CI 87-94.9) at month 6 and 94.7% (95% CI 90.3-97.1) at month 12. Sub-optimal adherence was influenced by: Medical and medication related barriers, mobility and travel, limited access and availability of PrEP pills, lifestyle-related factors, inadequate PrEP knowledge and low perceived benefits of PrEP, non-disclosure PrEP use and, low perceived HIV risk. Participants recommended modifying PrEP dosing, introducing multiple dosing options at the PrEP care clinic, enhancing counselling sessions, and ensuring continuous availability of PrEP pills. The prevalence of suboptimal PrEP adherence is high among female sex workers in Tanzania. The study underscores the need for implementation research on the introduction of multiple dosing modalities, coupled with improved availability and accessible PrEP services and tailored counselling programs.