1 Department of Clinical Research, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK; The Desmond Tutu HIV Centre, and Clinical Infectious Diseases Research Initiative; Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, Republic of South Africa. Electronic address: stephen.lawn@lshtm.ac.uk.
2 The Desmond Tutu HIV Centre, and Clinical Infectious Diseases Research Initiative; Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, Republic of South Africa; The Francis Crick Institute Mill Hill Laboratory, London, UK; Department of Medicine, Imperial College, London, UK.