Author information: (1)Cambridge University NHS Hospitals Foundation Trust, Cambridge, United Kingdom. (2)Clinical Microbiology & Public Health Laboratory, Public Health England, Cambridge, United Kingdom. (3)Medical Research Council Biostatistics Unit, University of Cambridge, Cambridge, United Kingdom. (4)Statistical Laboratory, Centre for Mathematical Sciences, University of Cambridge, Cambridge, United Kingdom. (5)Cambridge Institute of Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, United Kingdom. (6)Department of Medicine, University of Cambridge, Cambridge, United Kingdom. (7)Occupational Health and Wellbeing, Cambridge Biomedical Campus, Cambridge, United Kingdom. (8)Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom. (9)Cambridge COVID-19 Testing Centre and AstraZeneca, Anne McLaren Building, Cambridge, United Kingdom. (10)NHS Blood and Transplant, Cambridge, United Kingdom. (11)Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom. (#)Contributed equally