Adolescents represent a growing proportion of people living with HIV worldwide and the highest risk population group for treatment attrition and AIDS-related mortality. There is an urgent need to design, implement, and test interventions that keep young people in HIV treatment and care. However, previous systematic reviews show scarce and inconclusive evidence of effective interventions for this age group. Recent years have seen an increase in focus on adolescent health and a rapidly changing programmatic environment. This systematic review article provides an evidence update by synthesizing empirical evaluations of interventions designed to improve antiretroviral therapy adherence and retention among adolescents (10-19) and youth (15-24) living with HIV, published between January 2016 and June 2018. A search of 11 health and humanities databases generated 2425 citations and 10 relevant studies, the large majority conducted in sub-Saharan Africa. These include six clinic-level interventions, one individual-level m-Health trial, and three community-or householdlevel interventions. Implications of their findings for future programming and research with young adults are discussed, in relation to previous reviews and the broader empirical evidence in this area. Findings highlight the need to further develop and test multi-faceted interventions that go beyond health facilities, to address broader social barriers to adherence and retention. In particular, further intervention studies with adolescents (10-19) should be a priority, if we are to retain these young people in treatment and care and aspire to achieve the United Nation's Sustainable Development Goals and 90-90-90 targets.

IntroductionThere are two million HIV‐positive adolescents in southern Africa, and this group has low retention in care and high mortality. There is almost no evidence to identify which healthcare factors can improve adolescent self‐reported retention. This study examines factors associated with retention amongst antiretroviral therapy (ART)‐initiated adolescents in South Africa.MethodsWe collected clinical records and detailed standardized interviews (n = 1059) with all 10‐ to 19 year‐olds ever initiated on ART in all 53 government clinics of a health subdistrict, and community traced to include lost‐to‐follow‐up (90.1% of eligible adolescents interviewed). Associations between full self‐reported retention in care (no past‐year missed appointments and 85% past‐week adherence) and health service factors were tested simultaneously in sequential multivariate regression and marginal effects modelling, controlling for covariates of age, gender, urban/rural location, formal/informal housing, maternal and paternal orphanhood, vertical/horizontal HIV infection, overall health, length of time on ART and type of healthcare facility.ResultsAbout 56% of adolescents had self‐reported retention in care, validated against lower detectable viral load (AOR: 0.63, CI: 0.45 to 0.87, p = 0.005). Independent of covariates, five factors (STACK) were associated with improved retention: clinics Stocked with medication (OR: 3.0, CI: 1.6 to 5.5); staff with Time for adolescents (OR: 2.7, CI: 1.8 to 4.1); adolescents Accompanied to the clinic (OR: 2.3, CI: 1.5 to 3.6); enough Cash to get to clinic safely (OR: 1.4, CI: 1.1 to 1.9); and staff who are Kind (OR: 2.6, CI: 1.8 to 3.6). With none of these factors, 3.3% of adolescents reported retention. With all five factors, 69.5% reported retention.ConclusionsThis study identifies key intervention points for adolescent retention in HIV care. A basic package of clinic and community services has the potential to STACK the odds for health and survival for HIV‐positive adolescents.