University of the Witwatersrand - South African Medical Research Council, University of the Witwatersrand - South African Medical Research Council, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, University of the Witwatersrand - School of Clinical Medicine, African Population and Health Research Center (APHRC), African Population and Health Research Center (APHRC), University of Limpopo, University of Limpopo, Australian National University (ANU), University of the Witwatersrand - South African Medical Research Council, affiliation not provided to SSRN, University of the Witwatersrand - South African Medical Research Council, University of the Witwatersrand - South African Medical Research Council, University of the Witwatersrand - South African Medical Research Council and University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit

National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, Centers for Disease Control and Prevention (CDC) - Influenza Division, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, University of the Witwatersrand - Perinatal HIV Research Unit, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, University of the Witwatersrand - Perinatal HIV Research Unit, Chris Hani Baragwanath Academic Hospital - Perinatal HIV Research Unit, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, South African Medical Research Council - Health Systems Research Unit, North-West University - Unit for Environmental Sciences and Management, North-West University - Unit for Environmental Sciences and Management, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, Government of the United States of America - Division of Influenza and Independent

University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, University of North Carolina (UNC) at Chapel Hill - Department of Epidemiology, University of North Carolina (UNC) at Chapel Hill - Carolina Population Center, University of Edinburgh - College of Medicine & Veterinary Medicine, University of Edinburgh - College of Medicine & Veterinary Medicine, National Health Laboratory Services (NHLS) - Centre for Respiratory Diseases and Meningitis, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit and University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit

University of Göttingen - Centre for Modern Indian Studies, University of the Witwatersrand - South African Medical Research Council, Harvard University - Center for Population and Development Studies, Harvard University - Center for Population and Development Studies, University of Göttingen - Centre for Modern Indian Studies, University of the Witwatersrand - South African Medical Research Council, Harvard University - Center for Population and Development Studies, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, University of the Witwatersrand - MRC/Wits Rural Public Health and Health Transitions Research Unit, Harvard University - Center for Population and Development Studies and Heidelberg University - Heidelberg Institute of Global Health