[1] Queens Univ, Ctr Infect & Immun, Belfast, Antrim, North Ireland
[2] ICS Trials Grp, Kadoorie Ctr, Oxford, England
[3] Vanderbilt Univ, Sch Med, Dept Med, Nashville, TN 37212 USA
[4] Watford Dist Gen Hosp, Anaesthet & Crit Care Unit, Watford, England
[5] Univ Warwick, Warwick Med Sch, Warwick, England