[1] Univ Bristol, Bristol Med Sch, Natl Inst Hlth Res Hlth Protect Res Unit NIHR HPRU, Bristol, England
[2] London Sch Hyg & Trop Med, Natl Inst Hlth Res Hlth Protect Res Unit NIHR HPRU, Keppel St, London, England
[3] NHS England South West, Taunton, England
[4] Sirona Care & Hlth, Sch aged Immunisat Team, Bristol, England
[5] Bristol City Council, Communities & Publ Hlth Team, Bristol, England
[6] UK Hlth Secur Agcy, Immunisat & Vaccine Preventable Dis Div, London, England
[7] Univ Hosp Bristol & Weston NHS Fdn Trust, Natl Inst Hlth Res Appl Res Collaborat West NIHR A, Bristol, England
[8] Univ Bristol Sch Med, Populat Hlth Sci, 39 Whatley Rd, Bristol BS8 2PS, England