1. Ministry of Health, Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso
2. Institute of Public Health, Medical School, Ruprecht-Karls-University, Heidelberg, Germany
3. Institut für medizinische Biometrie und Epidemiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
4. Research Centre for Vitamins and Vaccines, Bandim Health Project, Statens Serum Institut, Copenhagen, Denmark
5. Bandim Health Project, Bissau, Guinea-Bissau