Johns Hopkins University - International Vaccine Access Center, Tropical Diseases Research Centre, Johns Hopkins University - International Vaccine Access Center, Tropical Diseases Research Centre, Tropical Diseases Research Centre, Tropical Diseases Research Centre, Tropical Diseases Research Centre - Department of Clinical Sciences, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, Ministry of Health Zambia, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, Government of the United States of America - Centers for Disease Control and Prevention (CDC), Johns Hopkins University - Bloomberg School of Public Health, Johns Hopkins University, Johns Hopkins University - Department of International Health, International Vaccine Access Center, Johns Hopkins University - Department of International Health, International Vaccine Access Center and Johns Hopkins University