1. Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine , London , UK
2. Department of Dermatology and Department of Biostatistics and Epidemiology, University of Pennsylvania , Philadelphia, PA , USA
3. School of Primary Care, Population Sciences and Medical Education, University of Southampton , Southampton , UK
4. UK Health Security Agency , London , UK
5. Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine , London , UK
6. Faculty of Population Health Sciences, University College London , London , UK