1 Immunisation and Vaccine Preventable Diseases Division, UKHSA, 61 Colindale Avenue, London, United Kingdom. Electronic address: clarissa.oeser@ukhsa.gov.uk.
2 Statistics Modelling and Economics Department, UKHSA, 61 Colindale Avenue, London, United Kingdom.
3 Sero-epidemiology Unit, UKHSA, Public Health Laboratory Manchester, Manchester Royal Infirmary, Oxford Road, Manchester, United Kingdom.
4 UK Health Security Agency, Porton Down, Salisbury, United Kingdom.
5 Immunisation and Vaccine Preventable Diseases Division, UKHSA, 61 Colindale Avenue, London, United Kingdom; Statistics Modelling and Economics Department, UKHSA, 61 Colindale Avenue, London, United Kingdom; Sero-epidemiology Unit, UKHSA, Public Health Laboratory Manchester, Manchester Royal Infirmary, Oxford Road, Manchester, United Kingdom; UK Health Security Agency, Porton Down, Salisbury, United Kingdom; Reference Laboratories, UKHSA, 61 Colindale Avenue, London, United Kingdom.
6 Immunisation and Vaccine Preventable Diseases Division, UKHSA, 61 Colindale Avenue, London, United Kingdom.