1. Vaccine Preventable Bacteria Section, Public Health England – National Infection Service, Colindale Avenue, London, NW9 5EQ, UK
2. Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104, USA
3. Statistics, Modelling and Economics Department, Public Health England – National Infection Service, Colindale Avenue, London, NW9 5EQ, UK
4. Department of Respiratory Medicine, Nottingham University Hospitals NHS Trust, Nottingham, UK
5. Immunisation and Countermeasures Division, Public Health England – National Infection Service, Colindale Avenue, London, NW9 5EQ, UK