Affiliation: | a NHS Mid Essex, Swift House, Chelmsford CM2 5PF, UK b NHS Nottingham City, Nottingham, UK c School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, UK d Cheshire and Merseyside Health Protection Unit, Liverpool, UK e Oncology Unit, Nottingham City Hospital, Nottingham, UK f Research Design Service for the East Midlands, School of Community Health Sciences, University Park, Nottingham, UK g Health Protection Agency East Midlands, Nottingham City Hospital, Nottingham, UK |