1 UCL Institute of Health Informatics, University College London, London, UK.
2 The Vaccine Centre, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
3 The Vaccine Centre, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK; Vaccines & Immunity Theme, MRC Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia.
4 The Vaccine Centre, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK. Electronic address: edward.parker@lshtm.ac.uk.