1. From the Centre for Infection, St George's, University of London, London, United Kingdom (HG, YZ, GEG, and DCM); the MRC International Nutrition Group, London School of Hygiene and Tropical Medicine, London, United Kingdom (HG, JAS, and AMP); the Edward Jenner Institute for Vaccine Research, Compton, United Kingdom (DLW); the Medical Research Council Keneba, Keneba, Gambia (JAS, PTN, and AMP); th