PROJECT SUMMARY / ABSTRACT This proposal is to develop and implement methods for quantifying geographic disparities, within Sub-Saharan African countries, in the opportunity for people living with HIV (PLHIV) to access antiretroviral therapy (ART); and to identify optimal strategies for reducing such disparities. The methods that we will develop constitute a novel analytic framework, which we will use to complete our three Specific Aims: (1) First, we will develop a spatial interaction model which can be applied in any SSA country to estimate the geographic opportunity to access ART and to identify disparities in this opportunity. We will apply the model to Malawi, which has one of the most severe HIV epidemics in the world, and where our previous studies have shown that PLHIV face substantial geographic disparities in accessing HIV care. To do so we will analyze a series of datasets, including the nationwide Malawi Population-based HIV Impact Assessments [MPHIAs]; the MPHIAs were collected in 2015/16 and 2020/21, spanning a period when ART coverage increased substantially. (2) Second, we will quantify the geographic relationship between the opportunity to access ART and its actual utilization, and determine the degree to which this relationship changed between the two timepoints. (3) Third, we will use our modeling framework in further analyses of the MPHIA 2020/21 dataset with the objective of identifying optimal strategies to reduce geographic disparities in the opportunity to access ART; both through the location of new healthcare facilities (HCFs) and through the allocation of additional supplies of ART. We will conduct these studies through a U.S.-Malawi collaborative team.