1. College of Public Health and Health Informatics, King Saud bin Abdulaziz University for Health Sciences, Riyadh 11632, Saudi Arabia
2. Public Health Policy Evaluation Unit, School of Public Health, Imperial College London, London SW7 2AZ, UK
3. Saw Swee Hock School of Public Health, University of Singapore, Singapore 117549
4. Field Epidemiology Service South East and London, Public Health England, London SE1 6LH, UK
5. Imperial College Healthcare NHS Trust, London SW7 2AZ, UK