Affiliation: | 1.National Institute of Hygiene and Epidemiology, Hanoi, Vietnam;2.University of the Philippines Manila-National Institutes of Health, Manila, Philippines;3.National Expanded Programme on Immunization, Hanoi, Vietnam;4.Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America;5.Menzies School of Health Research, Casuarina, Northern Territory, Australia |