1. Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom
2. NIHR Health Protection Research Unit (HPRU) in Immunisation, London, United Kingdom
3. Immunisation and Countermeasures Division, Public Health England, Colindale, United Kingdom
4. The Phoenix Partnership (TPP) (Leeds) Ltd, Leeds, United Kingdom
5. Statistics, Modelling and Economics Department, Public Health England, Colindale, United Kingdom