Table 1 Distribution of population characteristics by serostatus at baseline (n and %)
Characteristic |  | Total (n = 2328) | SARS-CoV-2 serology Neutralising antibodies at baseline | |
|---|---|---|---|---|
Seronegative (n = 2005) | Seropositive (n = 323) | |||
Gender | Female | 1898 (81.5) | 1629 (81.2) | 269 (83.3) |
Male | 430 (18.5) | 376 (18.8) | 54 (16.7) | |
Age category |  ≤ 35 | 757 (32.5) | 642 (32.0) | 115 (35.6) |
36–49 | 756 (32.5) | 673 (33.6) | 83 (25.7) | |
 ≥ 50 | 815 (35.0) | 690 (34.4) | 125 (38.7) | |
Hospital staff role | Physician | 282 (12.1) | 254 (12.7) | 28 (8.7) |
Nurse | 731 (31.4) | 600 (29.9) | 131 (40.6) | |
Administrative | 499 (21.4) | 428 (21.3) | 71 (22.0) | |
Other | 816 (35.1) | 723 (36.1) | 93 (28.8) | |
Direct contact with patients* | No patient contact | 612 (26.3) | 540 (26.9) | 72 (22.3) |
With non-COVID patients | 504 (21.6) | 441 (22.0) | 63 (19.5) | |
With COVID patient | 1212 (52.1) | 1024 (51.1) | 188 (58.2) | |
COVID-19 dedicated ward | Intensive to medium care | 347 (14.9) | 314 (15.7) | 33 (10.2) |
Emergency | 145 (6.2) | 116 (5.8) | 29 (9.0) | |
Infectious disease | 149 (6.4) | 125 (6.2) | 24 (7.4) | |
Pulmonology | 203 (8.7) | 174 (8.7) | 29 (9.0) | |
Smoker | No | 1492 (64.1) | 1269 (63.3) | 223 (69.0) |
Former | 653 (28.0) | 567 (28.3) | 86 (26.6) | |
Current | 183 (7.9) | 169 (8.4) | 14 (4.3) | |
Chronic respiratory disease | No | 2162 (92.9) | 1851 (92.3) | 311 (96.3) |
Yes | 166 (7.1) | 154 (7.7) | 12 (3.7) | |
Diabetes Mellitus | No | 2296 (98.6) | 1980 (98.8) | 316 (97.8) |
Yes | 32 (1.4) | 25 (1.2) | 7 (2.2) | |
Cardiovascular disease | No | 2144 (92.1) | 1852 (92.4) | 292 (90.4) |
Yes | 184 (7.9) | 153 (7.6) | 31 (9.6) | |
Immune disorder | No | 2277 (97.8) | 1961 (97.8) | 316 (97.8) |
Yes | 51 (2.2) | 44 (2.2) | 7 (2.2) | |
Use of NSAID | No | 2264 (97.3) | 1946 (97.1) | 318 (98.5) |
Yes | 64 (2.7) | 59 (2.9) | 5 (1.5) | |
Use of antihypertensive medications | No | 2183 (93.8) | 1880 (93.8) | 303 (93.8) |
Yes | 145 (6.2) | 125 (6.2) | 20 (6.2) | |
Use of immunosuppressants | No | 2271 (97.6) | 1951 (97.3) | 320 (99.1) |
Yes | 57 (2.4) | 54 (2.7) | 3 (0.9) | |
BCG vaccine received between 1940 and 2020 | No | 1739 (74.7) | 1505 (75.1) | 234 (72.4) |
| Â | Yes | 251 (10.8) | 221 (11.0) | 30 (9.3) |
| Â | Unknown | 338 (14.5) | 279 (13.9) | 59 (18.3) |
Influenza vaccine season 2019/20 | No | 1264 (54.3) | 1063 (53.0) | 201 (62.2) |
Yes | 1064 (45.7) | 942 (47.0) | 122 (37.8) | |
Travel to other European country* | No | 1699 (73.0) | 1472 (73.4) | 227 (70.3) |
Yes | 629 (27.0) | 533 (26.6) | 96 (29.7) | |
Number of household members# | 1 | 266 (11.4) | 227 (11.3) | 39 (12.1) |
2 | 787 (33.8) | 688 (34.3) | 99 (30.7) | |
3 | 352 (15.1) | 307 (15.3) | 45 (13.9) | |
4 | 630 (27.1) | 535 (26.7) | 95 (29.4) | |
 ≥ 5 | 293 (12.6) | 248 (12.4) | 45 (13.9) | |
Children ≤ 11 yrs in the household | No | 1660 (71.3) | 1419 (70.8) | 241 (74.6) |
Yes | 668 (28.7) | 586 (29.2) | 82 (25.4) | |
Dog owner | No | 1878 (80.7) | 1607 (80.1) | 271 (83.9) |
Yes | 450 (19.3) | 398 (19.9) | 52 (16.1) | |
Cat owner | No | 1806 (77.6) | 1541 (76.9) | 265 (82.0) |
Cat outside | 393 (16.9) | 348 (17.4) | 45 (13.9) | |
Cat inside | 129 (5.5) | 116 (5.8) | 13 (4.0) | |
Province of residence | North Brabant | 927 (39.8) | 746 (37.2) | 181 (56.0) |
North Holland | 137 (5.9) | 121 (6.0) | 16 (5.0) | |
South Holland | 554 (23.8) | 497 (24.8) | 57 (17.6) | |
Gelderland | 353 (15.2) | 323 (16.1) | 30 (9.3) | |
Limburg | 200 (8.6) | 166 (8.3) | 34 (10.5) | |
Groningen | 157 (6.7) | 152 (7.6) | 5 (1.5) | |
SARS-CoV-2 RT-PCR | Symptomatic | |||
 Positive | 112 (16.8) | 16 (3.1) | 96 (65.8) | |
 Negative | 556 (83.2) | 506 (96.6) | 50 (34.2) | |
Asymptomatic | ||||
 Positive | 0 (0.0) | 0 (0.0) | 0 (0.0) | |
 Negative | 52 (100.0) | 46 (100.0) | 6 (100.0) | |