Acknowledgements
The authors would like to acknowledge the staff of the University of Birmingham Clinical Immunology Service for facilitating laboratory studies. The convalescent health care worker study COCO was carried out at the National Institute for Health Research (NIHR)/Wellcome Trust Birmingham Clinical Research Facility.
This study was funded as part of the UK Coronavirus Immunology Consortium funded by NIHR and UKRI. This paper presents independent research supported by the NIHR Birmingham Biomedical Research Centre at the University Hospitals Birmingham NHS Foundation Trust and the University of Birmingham.