[1] Univ Plymouth, Fac Hlth, Sch Nursing & Midwifery, Plymouth, England
[2] Univ Northampton, Fac Hlth, Northampton, England
[3] Univ Washington, Dept Family Med, Seattle, WA USA
[4] Univ Oxford, Nuffield Dept Primary Care Hlth Sci, Oxford, England
[5] Leicester Royal Infirm, Childrens Emergency Dept, Paediat Emergency Med Leicester Acad PEMLA Grp, Leicester, England
[6] Univ Leicester, SAPPHIRE Grp, Hlth Sci, Leicester, England
[7] UCL, UCL Great Ormond St Inst Child Hlth, UCL Populat Policy & Practice Res & Teaching Dept, London WC1N 1EH, England
[8] Whittington Hlth NHS, Community Paediat, London N19 5NF, England