[1] Univ Cambridge, Sch Clin Med, Inst Publ Hlth, Cambridge Ctr Hlth Serv Res, Forvie Site, Cambridge, England
[2] Univ Exeter, Sch Med, Exeter, Devon, England
[3] Open Univ, Fac Hlth & Social Care, Milton Keynes, Bucks, England
[4] Univ Cambridge, Sch Clin Med, Inst Publ Hlth, Primary Care Unit, Forvie Site, Cambridge, England
[5] Ipsos MORI, London, England
[6] Univ Exeter, Sch Med, Exeter, Devon, England
[7] RAND Corp, Santa Monica, CA USA