[1] Univ Oxford, Churchill Hosp, Oxford Resp Trials Unit, Oxford OX3 7LJ, England
[2] Univ Wales Hosp, Dept Resp Med, Cardiff CF4 4XW, S Glam, Wales
[3] Oxford Ctr Resp Med, Oxford, England
[4] MRC, Clin Trials Unit, London, England
[5] Univ Oxford, Oxford Biomed Res Ctr, Natl Inst Hlth Res, Oxford OX1 2JD, England
[6] Great Western Hosp, Swindon, Wilts, England
[7] James Cook Univ Hosp, Middlesbrough, Cleveland, England
[8] Univ Hosp Ayr, Ayr, Scotland
[9] Royal Berkshire Hosp, Reading, Wales
[10] Buckinghamshire Healthcare Natl Hlth Serv Trust, Amersham, Bucks, England
[11] Univ Western Australia, Sch Med & Pharmacol, Perth, WA 6009, Australia
[12] Univ Western Australia, Ctr Asthma Allergy & Resp Res, Perth, WA 6009, Australia
[13] UCL, Res Dept Infect & Populat Hlth, London WC1E 6BT, England