1. Immunization, Vaccines and Biologicals Department, World Health Organization, 1202 Geneva, Switzerland
2. Department of Social Policy, London School of Economics and Political Science, London WC2A 2AE, UK
3. Department of Health Policy and Administration, Faculty of Public Health, Universitas Indonesia, Depok 16424, Indonesia
4. Ethiopian Public Health Institute, Addis Ababa 1242, Ethiopia