1. School of Public Health, University of Ghana , P.O. Box LG13, Legon, Ghana
2. UNICEF, Health Programme , Belgravia, Harare, Zimbabwe
3. Social Policy and Social Protection, Programme Group, UNICEF , New York, NY 10017, USA
4. School of Public and International Affairs, Princeton University , Princeton, NJ 08540, USA
5. Nutrition Programme, UNICEF , New York, NY 10017, USA
6. Global Immunization Division, US Centers for Disease Control and Prevention , Atlanta, GA 30329, USA
7. Health Programme, UNICEF , New York, NY 10017, USA