1. Department of Virology, Statens Serum Institut, Copenhagen, Denmark.
2. Department of Paediatrics, University of Oxford, Oxford, United Kingdom.
3. The Bandim Health Project, Bissau, Guinea-Bissau.
4. Department of International Health, Immunology and Microbiology, Panum Institut, University of Copenhagen, Copenhagen, Denmark.
5. Department of Laboratory Medicine, Karolinska Institute, Stockholm, Sweden.