1. Field Epidemiology Service, Public Health England, Bristol, UK
2. Institute of Primary Care & Public Health, Cardiff University, Cardiff, UK
3. Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
4. School of Social and Community Medicine, University of Bristol, Bristol, UK
5. NIHR Health Protection Research Unit in Evaluation of Interventions, University of Bristol, Bristol, UK
6. NIHR Health Protection Research Unit in Emergency Preparedness and Response, King’s College London, London, UK