1. Health Economics Research Centre, Nuffield Department of Population Health, University of Oxford , Richard Doll Building, Old Road Campus, Oxford OX3 7LF, United Kingdom
2. Department of Population Health Sciences, King’s College London , Guy’s Campus, Great Maze Pond, London SE1 1UL, United Kingdom
3. Nuffield Department of Primary Care Health Sciences, University of Oxford , Radcliffe Primary Care Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG, United Kingdom