[1] Univ Bristol, Populat Hlth Sci, Bristol, Avon, England
[2] Univ Southampton, Primary Care & Populat Sci, Southampton, Hants, England
[3] Univ Nottingham, Ctr Evidence Based Dermatol, Nottingham, England
[4] Nottingham CityCare Partnership, Nottingham, England
[5] Univ Hosp Bristol NHS Fdn Trust, Bristol Royal Hosp Children, Bristol, Avon, England
[6] Univ Bristol, Bristol Randomised Trials Collaborat, Bristol Trials Ctr, Bristol, Avon, England
[7] Univ Bristol, Hlth Econ Bristol, Populat Hlth Sci, Bristol, Avon, England
[8] Univ Bristol, Ctr Acad Child Hlth, Populat Hlth Sci, Bristol, Avon, England
[9] Univ Nottingham, Div Primary Care, Nottingham, England
[10] Imperial Coll London, Sect Paediat, London, England