Table 2.
Prevalence of SARS-CoV-2 antibodies in first responders and association with seropositivity
| Total number of participants | Rate of seropositive participants | OR for being seropositive unadjusted |
AORa for being seropositive |
Total number of participants without prior self-reported SARS-CoV-2 infection (positive by PCR)b | Distribution among seropositive participants, but without prior self-reported SARS-CoV-2 infection (positive by PCR)b | |
|---|---|---|---|---|---|---|
| n (column-%) | n (row-%c) [95% CI] | OR [95% CI] | AOR [95% CI] | n (column-%) | n (row-%c) [95% CI] | |
| Total | 745 (100) | 34 (4) [3.1–6.2] | 723 (100) | 20 (3) [1.6–4.1] | ||
| Sex | ||||||
| Male | 682 (92) | 33 (5) [3.3–6.6] | Ref.d | Ref. | 660 (91) | 19 (2) [1.0–3.9] |
| Female | 62 (8) | 1 (1) [0.1–8.4] | 0.29 [0.0–2.9] | 0.22 [0.0–2.2] | 62 (9) | 1 (2) [1.0–8.7] |
| Missing | 1 (0) | – | – | – | 1 (0) | 0 (0) |
| Age group | ||||||
| 18–39 years | 375 (51) | 21 (5) [3.5–8.3] | Ref. | Ref. | 361 (40) | 12 (3) [1.7–5.6] |
| 40 years and older | 355 (49) | 12 (3) [1.7–5.6] | 0.57 [0.3–1.2] | 0.53 [0.3–1.2] | 347 (47) | 7 (2) [0.8–3.9] |
| Missing | 15 (2) | 1 (7) [0.1–29.8] | – | – | 15 (3) | 1 (7) [0.1–29.8] |
| Household size | ||||||
| One person | 120 (16) | 9 (7) [3.8–13.5] | Ref. | Ref. | 116 (16) | 7 (6) [2.8–11.8] |
| Two persons | 254 (34) | 10 (4) [2.0–6.9] | 0.49 [0.2–1.3] | 0.54 [0.2–1.4] | 246 (34) | 3 (1) [3.2–11.4] |
| Three or more persons | 369 (450) | 15 (4) [2.3–6.4] | 0.51 [0.2–1.2] | 0.52 [0.2–1.3] | 359 (50) | 10 (3) [1.3–4.9] |
| Missing | 2 (0) | – | – | – | 2 (0) | 0 (0) |
| Level of education | ||||||
| Lower/middle | 383 (51) | 16 (4) [2.6–6.8] | Ref. | Ref. | 369 (51) | 7 (2) [0.7–3.7] |
| Higher | 348 (47) | 18 (5) [2.9–7.5] | 1.02 (0.5–2.0) | 0.86 [0.4–1.8] | 340 (47) | 13 (4) [2.1–6.3] |
| Other/still a student | 9 (1) | 0 (0) | – | – | 9 (1) | 0 (0) |
| Missing | 5 (1) | 0 (0) | – | – | 5 (1) | 0 (0) |
| Work taske | ||||||
| Firefighters | 540 (78) | 26 (5) [3.1–6.8] | 1.97 [0.6–6.2] | 1.80 [0.5–3.9] | 525 (73) | 14 (3) [1.4–4.3] |
| Paramedics: emergency rescue | 400 (60) | 24 (6) [3.4–8.6] | 2.52 [1.0–6.3] | 2.45 [0.8–7.5] | 386 (53) | 14 (3) [1.9–5.8] |
| Paramedics: patient transport | 162 (24) | 9 (5) [2.8–10.1] | 1.52 [0.6–3.5] | 1.39 [0.6–3.3] | 158 (22) | 7 (4) [2.0–8.7] |
| Technicians administrative official | 108 (17) | 2 (2) [0.3–6.3] | 0.35 [0.1–1.8] | 0.44 [0.1–2.3] | 107 (15) | 2 (2) [0.3–6.3] |
| Chronic condition | ||||||
| No | 620 (83) | 29 (5) [3.1–6.5] | Ref. | Ref. | 605 (84) | 18 (3) [1.7–4.5] |
| Yes | 121 (16) | 5 (4) [1.6–9.2] | 0.87 [0.3–2.4] | 1.22 [0.4–3.5] | 115 (16) | 2 (2) [0.3–6.0] |
| Missing | 0 (0) | – | – | 3 (0) | – | |
| PCR test since February 2020 | ||||||
| Yes | 260 (35) | 20 (8) [4.9–11.5] | Ref. | Ref. | 240 (33) | 6 (2) [1.0–5.2] |
| No, no test needed | 394 (53) | 12 (3) [1.6–5.1] | 0.36 [0.2–0.8] | 0.35 [0.2–0.8] | 394 (55) | 12 (3) [1.6–5.1] |
| No, but I thought about getting tested and I asked for one, but did not get one | 89 (12) | 2 (2) [0.4–7.7] | 0.26 [0.0–1.5] | 0.27 [0.0–1.3] | 89 (12) | 2 (2) [0.4–7.7] |
| Missing | 2 (0) | 0 (0) | – | – | 0 (0) | 0 (0) |
| Self-reported COVID-19 | ||||||
| Negative | 236 (32) | 6 (2) [1.0–5.3] | Ref. | Ref. | – | – |
| Positive | 20 (3) | 14 (70) [48.2–85.8] | 21.73 [6.7–68.7] | 18.54 [6.0–57.6] | – | – |
| I don’t know | 3 (0) | 0 (0) | – | – | – | – |
| Symptoms since February 2020f | ||||||
| Fever ≥38°C | 80 (11) | 6 (7) [3.3–15.3] | 1.86 [0.9–4.8] | 1.78 [0.7–4.6] | 77 (11) | 4 (5) [1.8–12.5] |
| Cough | 222 (30) | 16 (7) [4.3–11.3] | 2.23 [1.1–4.6] | 2.27 [1.1–4.8] | 212 (30) | 8 (4) [1.7–7.1] |
| Pneumonia | 6 (1) | 1 (17) [0.7–56.5] | 4.39 [0.5–39.7] | 4.29 [0.5–39.1] | 5 (1) | 0 (0) |
| Dyspnea or shortness of breath | 32 (4) | 6 (19) [8.7–35.4] | 5.85 [2.2–15.6] | 7.67 [2.7–20.4] | 25 (4) | 0 (0) |
| Pain when breathing | 21 (3) | 1 (5) [0.0–22.6] | 1.04 [0.1–8.7] | 1.02 [0.1–8.5] | 20 (3) | 0 (0) |
| Congested nose | 283 (38) | 20 (7) [4.4–10.5] | 2.50 [1.2–5.2] | 2.58 [1.2–5.5] | 274 (38) | 12 (4) [2.3–7.3] |
| Sore throat | 255 (35) | 16 (6) [4.2–11.1] | 1.78 [0.9–3.6] | 1.77 [0.8–3.7] | 244 (34) | 8 (3) [1.5–6.2] |
| Loss of smell | 23 (3) | 12 (52) [33.0–71.1] | 36.9 [14.4–94.6] | 45.6 [16.4–127.3] | 11 (2) | 1 (9) [0.3–37.8] |
| Loss of taste | 18 (2) | 8 (45) [24.5–66.5] | 22.7 [8.1–63.3] | 24.1 [8.3–69.8] | 10 (1) | 1 (10) [0.3–40.5] |
| No symptoms | 252 (34) | 2 (1) [0.0–2.7] | 0.09 [0.0–0.6] | 0.03 [0.0–1.9] | 248 (34) | 1 (0) [0.0–2.1] |
| Contact to a confirmed COVID-19 case | ||||||
| No | 387 (52) | 9 (2) [1.0–4.2] | Ref. | Ref. | 384 (53) | 8 (2) [0.9–3.9] |
| Yes, with a distance ≥1.5m | 121 (16) | 3 (2) [0.7–6.9] | 1.85 [0.7–4.8] | 1.84 [0.7–4.7] | 119 (17) | 2 (2) [0.3–5.8] |
| Yes, with a distance <1.5m | 234 (31) | 21 (9) [5.8–13.2] | 7.3 [4.3–12.4] | 7.5 [4.3–12.8] | 219 (30) | 10 (4) [2.3–8.1] |
| Missing | 3 (0) | 1 (33) [1.5–75.6] | – | – | 1 (0.1) | 0 (0) |
| Other exposure | ||||||
| Working with patients | 398 (54) | 22 (5) [3.5–8.1] | 1.66 [0.8–3.5] | 1.51 [0.7–3.8] | 382 (53) | 12 (3) [1.6–5.2] |
| Working with customers | 123 (17) | 3 (2) [0.6–6.8] | 1.28 [0.7–2.4] | 1.36 [0.8–2.4] | 109 (15) | 1 (1) [−0.2 to 4.4] |
| Attended an event with ≥50 persons | 253 (34) | 16 (6) [3.8–9.9] | 1.78 [0.9–3.7] | 1.65 [0.8–3.5] | 246 (34) | 10 (4) [2.0–7.2] |
| Travelled outside the EU | 43 (6) | 2 (5) [1.1–15.4] | 1.01 [0.2–4.7] | 0.95 [0.2–4.3] | 41 (6) | 0 (0) |
| Travelled within the EU | 268 (36) | 15 (5) [3.2–8.9] | 1.44 [0.7–3.0] | 1.59 [0.8–3.3] | 258 (36) | 7 (3) [1.1–5.3] |
| Adherence to public health measures | ||||||
| Adheres completely | 438 (59) | 22 (5) [3.2–7.3] | Ref. | Ref. | 420 (58) | 10 (2) [1.1–4.2] |
| Adheres partly | 300 (40) | 11 (4) [1.9–6.3] | 1.85 [0.7–4.8] | 1.84 [0.7–4.7] | 297 (41) | 9 (3) [1.4–5.5] |
| Missing | 7 (1) | 1 (14) [0.5–51.5] | 7.31 [4.3–12.4] | 7.52 [4.3–12.8] | 6 (1) | 1 (17) [0.7–56.5] |
aAOR = adjusted odds ratio for age and sex.
bFor the analysis of subjects with antibodies but without self-reported SARS-CoV-2 infection, all subjects with positive PCR test (n = 20) or unknown PCR result (n = 2) were excluded. Therefore, the sample size for this group was 723 individuals.
cThis is the test-adjusted seroprevalence.
dref = reference group.
eOne person could work in more than one field.
fMultiple choices possible.