Study sample characteristics
| Total sample | No prior SARS-CoV-2 infection | Prior SARS-CoV-2 infection | P value* | |
| n | 843 | 784 | 59 | |
| Age in years, median (IQR) | 41.66 (35.19, 52.80) | 41.89 (35.25, 53.00) | 38.72 (34.93, 49.31) | 0.169 |
| Age in years (range) | 20.37–87.26 | 20.37–87.26 | 23.52–76.87 | |
| Male sex, n (%) | 256 (30.4) | 239 (30.5) | 17 (28.8) | 0.903 |
| Non-white race, n (%) | 405 (48.0) | 372 (47.4) | 33 (55.9) | 0.262 |
| Hispanic ethnicity, n (%) | 86 (10.2) | 73 (9.3) | 13 (22.0) | 0.004 |
| Obesity, n (%) | 103 (12.2) | 92 (11.7) | 11 (18.6) | 0.175 |
| Hypertension, n (%) | 128 (15.2) | 122 (15.6) | 6 (10.2) | 0.355 |
| Charlson Comorbidity Index, median (IQR)† | 0.00 (0.00, 1.00) | 0.00 (0.00, 1.00) | 0.00 (0.00, 1.00) | 0.572 |
| Work environment‡ | ||||
| ICU, COVID-19 unit | 135 (16.1) | 126 (16.2) | 9 (15.3) | 1.00 |
| ICU, non-COVID-19 unit | 133 (15.9) | 129 (16.5) | 4 (6.8) | 0.073 |
| Ward, COVID-19 unit | 160 (19.1) | 141 (18.1) | 19 (32.2) | 0.013 |
| Ward, non-COVID-19 unit | 204 (24.3) | 193 (24.7) | 11 (18.6) | 0.37 |
| Emergency department /urgent care | 98 (11.7) | 94 (12.1) | 4 (6.8) | 0.315 |
| Outpatient clinic | 215 (25.6) | 206 (26.4) | 9 (15.3) | 0.082 |
| Office | 129 (15.4) | 119 (15.3) | 10 (16.9) | 0.873 |
| Work from home | 61 (7.3) | 57 (7.3) | 4 (6.8) | 1.00 |
| Other | 185 (22.1) | 177 (22.7) | 8 (13.6) | 0.142 |
| Unknown | 74 (8.8) | 71 (9.1) | 3 (5.1) | 0.423 |
*P value comparing those with versus without prior SARS-CoV-2 infection.
†The Charlson Comorbidity Index weights the clinical conditions into a single score to predict 10-year survival: age, myocardial infarction, heart failure, peripheral vascular disease, stroke, dementia, chronic obstructive pulmonary disease, connective tissue disease, peptic ulcer disease, liver disease, diabetes mellitus, hemiplegia, chronic kidney disease, solid tumour, leukaemia, lymphoma and AIDS.
‡Participant-provided work environment. Participants could select multiple environments if they worked in more than one location.
ICU, intensive care unit.