1. Centre Hospitalier Universitaire de Bordeaux, Bordeaux, France
2. University Victor Segalen Bordeaux 2, School of Public Health, Bordeaux, France
3. Institut national de la santé et de la recherche médicale (National institute of health and medical research, INSERM), U897, Bordeaux, France
4. Statens Serum Institut, Copenhagen, Denmark
5. Institute of Child Health, London, United Kingdom