1 London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK; Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Tropical Medicine and International Health, Berlin, Germany.
2 London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK.
3 London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK; Biomedical Research and Training Institute, Harare, Zimbabwe.
4 Science Editor and Translator, Valencia, Spain.
5 London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK; Vaccines & Immunity Theme, Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Fajara, The Gambia.
6 London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK. Electronic address: robin.basu-roy@lshtm.ac.uk.