Overall Project Summary/Abstract Antiretroviral treatment (ART) options for pregnant women and children living with HIV have fallen behind those for adults, reflecting the substantial research gap for modern ART regimens in these groups. Safety and efficacy studies of specific ART regimens in pregnancy, and strategies for starting modern ART in early infancy, have become research priorities. Here we propose a series of interrelated projects that expand the scientific objectives and data utilization of a valuable NIH-funded nationwide birth surveillance system in Botswana (the Tsepamo Study), and connect it with the infrastructure provided by an existing program for identifying and treating infants with HIV (the Early Infant Treatment Study, or EIT). The four proposed projects, anchored by administrative and data cores, include: 1) Tsepamo Plus: Expanded Congenital Abnormalities Surveillance and an Emulated Clinical Trial to Evaluate Weight Impact on Birth Outcomes for Newer ART Regimens: an expanded surveillance program for neural tube defects and other congenital abnormalities following exposure to modern ART regimens, and an emulated clinical trial to address critical questions related to use of ART regimens by maternal weight strata. 2) Methodology: Developing Reporting Criteria for Pregnancy Surveillance Cohorts and New Techniques for Supporting Target Trials: the creation of surveillance reporting criteria in pregnancy cohorts and validation of a target trial approach to ART regimen comparisons. 3) Point-of-Care HIV Testing and Early Dolutegravir Use for Infants: a new approach to targeted facility- based point-of-care HIV testing, combined with an optimized ART management strategy that uses dolutegravir from early infancy. 4) Pioneering Precision Medicine Approaches for Immune Control of Pediatric HIV-1 Infection: utilizing shared data and infrastructure to efficiently obtain specimens, this project will bank HIV sequences from early- treated infants, measure and compare viral reservoir and chromosomal positioning between ART regimens, and study immune responses to mRNA vaccines among children with HIV to begin development of an mRNA HIV vaccine program for children in Botswana. This P01 brings together a group of experienced investigators who will forge a cohesive research program using the unique data sources and outstanding physical infrastructure available from the Tsepamo and EIT research programs in Botswana. Each project addresses key scientific issues related to ART use during pregnancy and initiation of ART in early infancy, and together they will efficiently close research gaps for women and children with HIV.