Introduction Anti-Retroviral Therapy (ART) use has increased globally. It is estimated that 15 million (41%) People Living with Human Immunodeficiency Virus (PLHIV) are receiving ART, out of which 823,000 are children. Adherence to ART influences viral load reduction, improved immunity and treatment success. Studies show an almost complete adherence is needed to sufficiently suppress viral replication. However, several factors, including poverty, substance abuse, stigma and lack of disclosure hinder success of adherence. While HIV prevalence has continued to decrease worldwide, it remains a major cause of morbidity and mortality among adolescents. Poor ART adherence increases the risk of viral drug-resistance, reduces future therapeutic options and increases the risk of transmission. Adherence has been studied extensively with adult patients, but adolescent adherence has been largely neglected in the literature.  Objective The aim of this study was to estimate prevalence of ART adherence and to identify characteristics of adolescents and their guardians that influence ART adherence.  Methods A cross sectional, facility-based study was carried out in four select facilities in Kajiado County. Quantitative and qualitative data was collected among 167 HIV positive adolescents and their guardians using interviewer questionnaires and an interviewer guide in two Focused Group Discussions. Data was managed using SPSS (version 22). Proportions and frequencies were calculated for categorical data and means and medians for continuous variables. Bivariate correlation analysis was conducted to determine strength and direction of associations between independent factors and adherence to ART. The t-test was used to conduct this evaluation at 5% level of significance. A linear regression model was fitted to control for confounders and adjust for association between factors and adherence to ART. Ethical clearance was sought and obtained from Moi Institutional Research and Ethics Committee (IREC).  Results A total of 167 adolescents aged 10-19 were interviewed among whom 49%(82) were males and 51%(95) females. Estimated level of adherence was 92.8% (95% CI: 87.8% – 95.8%). The most common reason for missing a dose was forgetting, fear of stigma and lack of food. Occupation, side effects, lack of food, having friends, confidentiality, trust and quality of care rating, swallowing drugs at the right time and keeping clinic appointments were significantly associated with adherence to ART (P<0.05) at the bivariate level. Adherence to ART was linearly modeled by two factors, “Experiencing side effects” and “Having friends who knew the adolescent’s status and cared for them”, F4, 157 = 22.302, p<0.05.  Conclusions This study found a prevalence rate slightly lower than the optimum and higher than most studies. Medication related factors were the most significant predictors of adherence.  Recommendations Adopt mechanisms to remind adolescents to take ART, improved regimen with reduced side effects, psychosocial support and stigma reduction strategies.

Keywords : Human Immunodeficiency Virus, Anti -Retroviral Therapy, Adolescent, Viral, Suppression, ART Adherence, Kajiado, Kenya.