1. Department of Population Health Sciences, University of Leicester , Leicester LE1 7RH , UK
2. National Institute for Health and Care Research (NIHR) Leicester Biomedical Research Centre , LE1 7RH , UK
3. Department of Respiratory Sciences, University of Leicester , Leicester LE1 9HN , UK
4. University Hospitals of Leicester NHS Trust , Leicester LE1 5WW , UK
5. Li Ka Shing Centre for Health Information and Discovery, Oxford Big Data Institute, University of Oxford , Oxford OX3 7LF , UK
6. Division of Country Health Programmes, WHO Regional Office for Europe , 2100 Copenhagen Ø , Denmark
7. Division of Country Health Policies and Systems, WHO Regional Office for Europe , 2100 Copenhagen Ø , Denmark
8. Division of Country Support, Emergency Preparedness and Response (CSE), WHO Regional Office for Europe , 2100 Copenhagen Ø , Denmark
9. Nottingham Centre for Epidemiology and Public Health, Lifespan and Population Health, University of Nottingham , Nottingham NG7 2UH , UK