1 Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya.
2 Amsterdam Institute for Global Health and Development, Department of Global Health, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
3 Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
4 GlaxoSmithKline, Vaccines, Nairobi, Kenya.
5 Departments of Global Health, Medicine, and Epidemiology, University of Washington, Seattle, WA, USA.