1. Faculty of Infectious and Tropical Diseases, Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
2. Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, UK
3. Centre for Statistics and Applications of University of Lisbon, Lisbon, Portugal
4. Pharmidex, 3rd Floor, 14 Hanover Street, London W1S 1YH, UK