Determinants of knowledge and positive perception of HIV pre-exposure prophylaxis: the role of age and sexual orientation in patients of specialized STI and transgender health services.

Pre-exposure prophylaxis (PrEP) is one of strategies for preventing human immunodeficiency virus infection. However, limited knowledge and perception of PrEP may impact the access to this prophylaxis. This study aimed to assess knowledge and perceptions of PrEP and to identify determinants, both sociodemographic and structural, associated with them among users of specialized public health services. This is a cross-sectional study based on data obtained through interviews conducted with patients who sought specialized services in STI on a spontaneous basis, as well as with routine patients at an outpatient clinic for transgender healthcare. A total of 142 users of the Brazilian Unified Health System services were interviewed. Eligible participants were individuals aged ≥ 18 years who sought care at the recruitment sites, were not currently using PrEP, and self-reported no prior HIV diagnosis. Data collection at these two locations took place between October 2021 and April 2022. Most participants were young, heterosexual, non-white men with higher education. Condom use was often inconsistent. Limited PrEP knowledge emerged as a major gap, while younger users showed a more favorable perception of PrEP. Understanding sociodemographic determinants of PrEP knowledge and perception highlights critical barriers and facilitators to its broader implementation. These findings may inform targeted strategies to enhance PrEP awareness, uptake, and adherence within Brazil's public health system.