PROJECT SUMMARY Mass treatment of preschool children with azithromycin (AZ) and routine administration of seasonal malaria chemoprevention (SMC), have been effective in reducing infections and mortality among children.5,22 However, it is not clear how concomitant use of sulfadoxine in SMC and AZ affects child morbidity and mortality. As mass distribution of AZ in sub-Saharan Africa is being scaled-up, research is needed to determine whether routine SMC administration enhances the effect of AZ and whether administering AZ in SMC or no SMC seasons is more beneficial for reducing child morbidity and mortality. Additionally, previous studies show healthcare access and utilization lower with increasing distance from facilities and with increasing community poverty, suggesting that mass treatment with antibiotics maybe more beneficial for communities with potentially less access to healthcare and less treatment/antibiotic exposure.13 Further research is needed to examine whether the effect of AZ varies by distance to healthcare facilities and community wealth and whether distant and poorer communities with less access to treatment would benefit more from AZ. The goal of the proposed research is to examine factors that may modify the effectiveness of AZ in reducing child morbidity and mortality. The study will examine whether the administration of SMC modifies the effect of AZ on child mortality and morbidity (Aim 1A and 1B) and assess whether distance from health facility (Aim 2A) and community wealth (Aim 2B) modify the effects of AZ on infectious morbidity and mortality among children. Analyses will use data collected from a cluster randomized trial (CRCT) of treatment with AZ vs placebo, along with primary healthcare surveillance, pre-census data and Burkina Faso’s National Malaria Control Program (NMCP) data. The proposal will provide valuable and timely insight on heterogeneity of the effect of AZ to help guide how, where and when to implement MDA AZ programs, which is a current research gap.17, 36 By providing insights on how to maximize the benefit of interventions that improve child health, knowledge gained from this research will advance the NICHD’s mission of increasing children’s survival and potential to live healthy and productive lives free from disease. The proposed training, guided by an exemplary mentorship team, will enhance the applicant’s expertise in infectious disease and social epidemiology, methods, and analyses of CRCT and surveillance data, and statistical methods for studying heterogeneity and interactions between interventions as well as principal component analysis. The methodological skills, research competency, and content expertise Elisabeth will gain will prepare her for a career as a future independent academic researcher focused on strategies to reduce infectious diseases and mortality among children.