[1] University of the Witwatersrand,MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences
[2] African Population and Health Research Centre (APHRC),MRC Mineral Metabolism Research Unit, Department of Paediatrics, Faculty of Health Sciences
[3] University of the Witwatersrand,Umeå Centre for Global Health Research, Department of Public Health and Clinical Medicine
[4] Umeå University,School of Public Health, Faculty of Health Sciences
[5] INDEPTH Network,Department of Paediatrics
[6] University of the Witwatersrand,undefined
[7] University of Cambridge,undefined