[1] UCL Inst Child Hlth, Gen & Adolescent Paediat Unit, London, England
[2] Univ Oxford, Dept Paediat, Oxford Vaccine Grp, Oxford, England
[3] Oxford Radcliffe Hosp NHS Trust, Dept Microbiol & Infect Dis, Oxford, England
[4] Univ London, Ctr Child Hlth, Barts & London Sch Med & Dent, London, England
[5] Univ Oxford, Dept Publ Hlth, Hlth Econ Res Ctr, Oxford, England
[6] NW London Hosp NHS Trust, Dept Microbiol, Harrow, Middx, England
[7] NW London Hosp NHS Trust, HPA Collaborating Lab, Harrow, Middx, England
[8] Univ Sydney, Natl Ctr Immunizat Res & Surveillance, Childrens Hosp Westmead, Sydney, NSW 2006, Australia