Characteristics of Orange County Fire Authority (OCFA) personnel who participated in SARS-CoV-2 IgG blood test (n=923) by case status and comparison with non-participants (n=78)
| Characteristic | Sero-prevalence | Cases n=49 n (%) | Non-cases n=874 n (%) | P value | Total participants n=923 n (%) | Non-participants n=78 n (%) | P value |
| Age group, years | 0.678 | 0.609 | |||||
| 21–30 | 4.5% | 5 (10.2) | 107 (12.2) | 112 (12.1) | 8 (10.3) | ||
| 31–40 | 6.2% | 20 (40.8) | 304 (34.8) | 324 (35.1) | 32 (41.0) | ||
| 41–50 | 4.2% | 12 (24.5) | 274 (31.4) | 286 (31.0) | 25 (32.0) | ||
| 51 and older | 6.0% | 12 (24.5) | 189 (21.6) | 201 (21.8) | 13 (16.7) | ||
| Sex | 0.454 | 0.660 | |||||
| Male | 5.5% | 49 (100) | 848 (97.0) | 897 (97.2) | 77 (98.7) | ||
| Female | 0% | 0 (0) | 26 (3.0) | 26 (2.8) | 1 (1.3) | ||
| Race | 0.446 | 0.999 | |||||
| White | 5.6% | 46 (93.9) | 781 (89.4) | 827 (89.6) | 70 (89.7) | ||
| Asian | 1.7% | 1 (2.0) | 59 (6.7) | 60 (6.5) | 5 (6.4) | ||
| Black | 0% | 0 (0) | 11 (1.3) | 11 (1.2) | 1 (1.3) | ||
| Mixed/other | 8.0% | 2 (4.1) | 23 (2.6) | 25 (2.7) | 2 (2.6) | ||
| Ethnicity | 0.782 | 0.114 | |||||
| Hispanic | 4.6% | 8 (16.3) | 166 (19.0) | 174 (18.9) | 21 (26.9) | ||
| Non-Hispanic | 5.5% | 41 (83.7) | 708 (81.0) | 749 (81.1) | 57 (73.1) | ||
| Job position and rank | 0.176 | 0.064 | |||||
| Battalion/other chief | 14.0% | 6 (12.3) | 37 (4.2) | 43 (4.6) | 0 (0) | ||
| Captain | 5.7% | 8 (16.3) | 132 (15.1) | 140 (15.2) | 2 (2.5) | ||
| Captain paramedic | 4.3% | 3 (6.1) | 66 (7.6) | 69 (7.5) | 0 (0) | ||
| Firefighter | 5.0% | 10 (20.4) | 192 (22.0) | 202 (21.9) | 12 (15.4) | ||
| Firefighter paramedic | 4.2% | 8 (16.3) | 182 (20.8) | 190 (20.6) | 3 (3.8) | ||
| Engineer | 6.5% | 9 (18.4) | 129 (14.8) | 138 (15.0) | 7 (9.0) | ||
| Engineer paramedic | 3.4% | 2 (4.1) | 57 (6.5) | 59 (6.4) | 1 (1.3) | ||
| Reserve firefighter | 0% | 0 (0) | 30 (3.4) | 30 (3.2) | 1 (1.3) | ||
| Support staff * | 0% | 0 (0) | 28 (3.2) | 28 (3.0) | 0 (0) | ||
| Missing† | 12.5% | 3 (6.1) | 21 (2.4) | 24 (2.6) | 52 (66.7) | ||
| Previous PCR test ‡ | 0.001 | 0.446 | |||||
| No | 2.1% | 13 (26.5) | 593 (67.8) | 606 (65.7) | 20 (25.6) | ||
| Yes—positive | 69.4% | 25 (51.0) | 11 (1.3) | 36 (3.9) | 0 (0) | ||
| Yes—negative | 3.1% | 8 (16.3) | 246 (28.1) | 254 (27.5) | 6 (7.7) | ||
| Missing† | 11.1% | 3 (6.1) | 24 (2.8) | 27 (2.9) | 52 (66.7) | ||
| Previous antibody test ‡ | 0.001 | 0.115 | |||||
| No | 4.4% | 30 (61.2) | 648 (74.1) | 678 (73.5) | 16 (20.5) | ||
| Yes— positive | 52.3% | 11 (22.5) | 10 (1.1) | 21 (2.3) | 0 (0) | ||
| Yes—negative | 2.5% | 5 (10.2) | 192 (22.0) | 197 (21.3) | 10 (12.8) | ||
| Missing† | 12.5% | 3 (6.1) | 24 (2.8) | 27 (2.9) | 52 (66.7) | ||
*Includes Fire Inspectors, Medical Educators, and Chaplains who participated in the TB testing campaign.
†Missing values are excluded from the χ2 tests.
‡Firefighters who had a prior positive PCR test and those with a prior positive antibody test were not mutually exclusive.