Occupational factors associated with SARS-CoV-2 positive serology among on-site workers (N=981)
| Total participants | SARS-CoV-2 seroprevalence | Prevalence (95% CI) | P value* | Adjusted PR (95% CI)† | |
| n (%) | n (%) | ||||
| On-site workers | 981 (79.4) | 86 (78.1) | 8.77 (7.15 to 10.71) | 0.56 | |
| Type of transport to work | |||||
| Private | 751 (76.6) | 66 (76.7) | 8.79 (6.96 to 11.04) | REF | |
| Public | 154 (15.7) | 15 (17.4) | 9.74 (5.95 to 15.54) | 1.32 (0.74 to 2.36) | |
| Private and public | 35 (3.6) | 2 (2.3) | 5.71 (1.43 to 20.19) | 0.63 (0.15 to 2.58) | |
| Walking | 37 (3.8) | 3 (3.5) | 8.11 (2.63 to 22.34) | 0.89 | 0.57 (0.14 to 2.35) |
| Working in a COVID-19 area | |||||
| No | 398 (40.6) | 29 (33.7) | 7.29 (5.11 to 10.29) | REF | |
| Yes | 545 (55.6) | 55 (63.9) | 10.09 (7.83 to 12.92) | 0.14 | 1.29 (0.81 to 2.06) |
| Type of and COVID-19 area‡ | |||||
| Non-assisting HCW and never worked in a COVID-19 area | 148 (15.1) | 7 (8.0) | 4.73 (2.27 to 9.6) | REF | |
| Non-assisting HCW and ever worked in a COVID-19 area | 230 (23.4) | 13 (15.1) | 5.65 (3.31 to 9.5) | 1.12 (0.44 to 2.82) | |
| Assisting HCW and never worked in a COVID-19 area | 244 (24.9) | 22 (25.6) | 9.02 (6.01 to 13.32) | 1.81 (0.77 to 4.26) | |
| Assisting HCW and ever worked in a COVID-19 area | 311 (31.7) | 40 (46.5) | 12.86 (9.57 to 17.07) | 0.006 | 2.45 (1.08 to 5.52) |
| p-trend | 0.26 | ||||
| Contact with COVID-19 cases | |||||
| No | 333 (33.9) | 23 (26.7) | 6.91 (4.63 to 10.18) | REF | |
| Yes | 536 (54.6) | 57 (66.3) | 10.63 (8.29 to 13.54) | 0.07 | 1.30 (0.77 to 2.20) |
| Contact with COVID-19 biological samples | |||||
| No | 646 (65.9) | 51 (59.3) | 7.89 (6.05 to 10.24) | REF | |
| Yes | 282 (28.7) | 30 (34.9) | 10.64 (7.54 to 14.81) | 0.17 | 1.09 (0.66 to 1.79) |
| Reporting to be exposed to COVID-19 by interacting with colleagues at work | |||||
| No | 242 (24.7) | 66 (76.7) | 2.89 (1.38 to 5.95) | REF | |
| Yes | 608 (62.0) | 7 (8.1) | 10.86 (8.62 to 13.59) | <0.0001 | 3.26 (1.49 to 7.15) |
| Reporting COVID-19 compatible symptoms | |||||
| No | 623 (63.5) | 15 (17.4) | 2.41 (1.46 to 3.96) | REF | |
| Yes | 306 (31.2) | 68 (79.1) | 22.22 (17.91 to 27.23) | <0.0001 | 9.53 (5.34 to 17.03) |
| Not following protection measures at work | |||||
| Felt protected with PPE | 132 (17.4) | 12 (16.9) | 9.09 (5.23 to 15.34) | 0.83 | 0.98 (0.51 to 1.88) |
| Colleagues cover themselves with their elbows when sneezing/coughing | 155 (15.8) | 21 (24.4) | 13.55 (9.00 to 19.90) | 0.01 | 1.70 (1.01 to 2.87) |
| 2 m safety distance from colleagues during lunch | 127 (14.1) | 12 (15.6) | 9.45 (5.44 to 15.91) | 0.71 | 1.06 (0.56 to 1.99) |
| Use of PPE with confirmed or suspicious COVID-19 patients | 79 (12.1) | 7 (10.45) | 8.86 (4.28 to 17.46) | 0.63 | 1.01 (0.45 to 2.26) |
| PPE removal safety | 48 (7.3) | 3 (4.6) | 6.25 (2.03 to 17.68) | 0.33 | 0.54 (0.17 to 1.74) |
| Personal use of mask | 34 (3.5) | 1 (1.2) | 2.94 (0.41 to 18.17) | 0.21 | 0.41 (0.06 to 2.99) |
| Colleagues use of surgical mask | 7 (0.7) | 1 (1.2) | 14.29 (1.96 to 58.12) | 0.62 | 1.68 (0.23 to 12.29) |
| Not following hand hygiene at work | |||||
| ≤7 times during workday | 233 (23.8) | 15 (17.4) | 6.44 (3.92 to 10.41) | 0.13 | 0.71 (0.39 to 1.28) |
| After money, phone and other personal tools manipulation | 175 (17.8) | 16 (18.6) | 9.14 (5.67 to 14.41) | 0.89 | 1.00 (0.58 to 1.74) |
| Every time entering in a new workspace | 102 (10.4) | 5 (5.8) | 4.90 (2.05 to 11.25) | 0.14 | 0.55 (0.22 to 1.37) |
| Before working | 21 (2.1) | 3 (3.5) | 14.29 (4.67 to 36.17) | 0.37 | 1.72 (0.54 to 5.47) |
| After finishing the workday | 17 (1.7) | 1 (1.2) | 5.88 (0.82 to 32.09) | 0.67 | 0.65 (0.09 to 4.72) |
| Before eating | 9 (0.9) | 2 (2.3) | 22.22 (5.59 to 57.95) | 0.16 | 2.67 (0.65 to 10.94) |
Numbers do not always sum up the total due to some missing value (none of the categories present more than 5% of missing values).
*χ2 test.
†Adjusted for sex, age (continuous), ICO centre, care staff, telework and cohabitants.
‡Assisting HCW: nurses, nursing assistants, resident physicians and specialists; otherwise, classified and non-assisting HCW.
HCW, healthcare worker; ICO, Institute of Oncology; PPE, personal protective equipment; PR, Prevalence Ratio.