RESUMEN
Background: A large percentage of the new cases of HIV/AIDs in Kenya are attributed to Key Populations (KPs). In Kenya, KPs contribute 33% of all new infections of HIV. It is with this realization that in 2017 the government of Kenya launched The Pre-Exposure Prophylaxis (PrEP) for HIV. The study aimed at assessing the factors influencing adherence to PrEP by KPs in Matayos sub-county, Busia County, Kenya. Methods: An analytical cross-sectional study that utilized a mixed-method data collection approach (n=343) was used to assessing the factors influencing adherence to PrEP by KPs in Matayos sub-county, Busia County, Kenya. Results: The level of adherence to PrEP using the Morisky Medical Adherence Scale-4 was established to be 37% among all KPs and 36%, 37% and 52% among CSWs, MSMs and PWIDs respectively. Chi-square analysis revealed significant relationship between Level of education (p=0.05), marital status (p=0.001), KP category (p=0.034), occupation (p=0.014), stigma (p=0.00), the perceptions of side effects (p=0.011), facility accessibility (P= 0.00), side effects (p=0.001) and adherence to PrEP. Among the MSMs condom use was established to have association to PrEP adherence (p=0.00). Conclusions: The study concluded that socio-demographic, individual characteristics, and clinical factors influence adherence to pre-exposure prophylaxis among key populations. The study recommended that key populations need more information on how to use pre-exposure prophylaxis, how it works, the side effects, what to do in case they experience the side effects and why adherence to pre-exposure prophylaxis is important.