Broad characteristics among healthcare workers assessed for antibody reactivity to spike SARS-CoV-2 protein in phase 1 and phase 2
| Overall* | Spike ELISA (AUC) positive in both phases | Negative reactivity to spike (AUC) in both phases | P value | |
| N=176 | n=68 | n=108 | ||
| Age, years | 44.7±12.4 | 42.9±11.9 | 45.8±12.7 | 0.099 |
| Female, gender | 111 (63.1%) | 40 (58.8%) | 71 (65.7%) | 0.467 |
| Race | 0.666 | |||
| Latinx | 54 (30.7%) | 21 (30.9%) | 33 (30.6%) | |
| Asian | 52 (29.5%) | 18 (26.5%) | 34 (31.5%) | |
| Black | 29 (16.5%) | 15 (22.1%) | 14 (13.0%) | |
| White | 31 (17.6%) | 10 (14.7%) | 21 (19.4%) | |
| Other | 10 (5.7%) | 4 (5.9%) | 6 (5.9%) | |
| Comorbidities | 54 (30.7%) | 25 (36.8%) | 29 (26.9%) | 0.214 |
| BCG vaccine received in childhood | 87 (49.4%) | 35 (51.5%) | 52 (48.1%) | 0.902 |
| COVID-19-related symptoms prior to phase 1 | 103 (58.5%) | 57 (83.8%) | 46 (42.6%) | <0.001 |
| Duration of symptoms | <0.001 | |||
| <7 days | 48 (46.6%) | 18 (31.0%) | 30 (66.7%) | |
| 7–14 days | 19 (18.4%) | 12 (20.7%) | 7 (15.6%) | |
| >14 days | 36 (35.0%) | 28 (48.3%) | 8 (17.8%) | |
| Time from symptom to positive result, days | 45.7±19.9 | 47.9±16.0 | 42.9±24.1 | 0.062 |
| RT-PCR positive result for SARS-CoV-2 prior to phase 1 | 51 (29.0%) | 49 (72.1%) | 2 (1.9%) | <0.001 |
| RT-PCR positive result for SARS-CoV-2 during phase 1 | 14 (8.0%) | 13 (19.1%) | 1 (0.9%) | <0.001 |
| Persisting symptoms from COVID-19 | 25 (14.2%) | 19 (27.9%) | 6 (5.6%) | <0.001 |
| Nature of work | 0.306 | |||
| Physicians | 81 (46.0%) | 29 (42.6%) | 52 (51.5%) | |
| Nurses | 29 (16.5%) | 15 (22.1%) | 14 (13.0%) | |
| Others | 64 (36.4%) | 24 (35.3%) | 40 (39.6%) | |
| Hospital areas worked in | ||||
| Emergency department/inpatient units | 118 (67.0%) | 50 (73.5%) | 68 (63.0%) | 0.141 |
| Ambulatory care/clinics | 72 (40.9%) | 27 (39.7%) | 45 (41.7%) | 0.631 |
| Administration/non-clinical care areas | 24 (13.6%) | 9 (13.2%) | 15 (13.9%) | 0.867 |
| Community exposure | 47 (26.7%) | 19 (27.9%) | 28 (25.9%) | 0.591 |
| Household exposure | 39 (22.2%) | 17 (25.0%) | 22 (20.4%) | 0.343 |
| PPE use at work | 173 (98.3%) | 67 (98.5%) | 106 (98.1%) | 0.226 |
| Use of face mask outside of the hospital | 158 (89.8%) | 58 (85.3%) | 100 (92.6%) | 0.062 |
Continuous variables are expressed as mean (SD), categorical variables as n (%).
*Demographic data are missing for two participants from the overall cohort.
AUC, area under the curve; PPE, personal protective equipment; RT-PCR, reverse transcription PCR.