Table 2

Conditional logistic multivariable regression models of influenza (model 1) in relation to the different dimensions of transmission and mitigation factors in a national case–control study covering 1 July 2006 to 31 December 2019

 Dimensions of transmission and mitigation factors Influenza ORs with 95% CI* All (N=14 971) Influenza A (N=11 300) Influenza B (N=3671) No of workers in close proximity to each other† <10 per day 1.12 (1.06 to 1.18) 1.14 (1.08 to 1.22) 1.05 (0.95 to 1.17) 10–30 per day 1.32 (1.25 to 1.40) 1.32 (1.24 to 1.41) 1.31 (1.18 to 1.47) >30 per day 1.40 (1.33 to 1.47) 1.42 (1.33 to 1.51) 1.34 (1.20 to 1.48) Nature of contacts† In workspaces with coworkers only 1.12 (1.06 to 1.18) 1.13 (1.06 to 1.20) 1.08 (0.97 to 1.20) In workspaces with general public 1.23 (1.17 to 1.30) 1.25 (1.17 to 1.32) 1.18 (1.06 to 1.31) Regular contacts with infected patients 1.64 (1.54 to 1.73) 1.67 (1.55 to 1.77) 1.57 (1.40 to 1.77) Contaminated workspaces† Frequently sharing material/surfaces with coworkers (≥10 times/day) 1.10 (1.00 to 1.20) 1.14 (1.07 to 1.21) 1.08 (0.97 to 1.20) Sometimes sharing material/surfaces with general public (<10 times/day) 1.13 (1.02 to 1.24) 1.08 (0.97 to 1.21) 1.05 (0.86 to 1.28) Frequently sharing materials/surfaces with general public (≥10 times/day) 1.41 (1.34 to 1.48) 1.43 (1.35 to 1.52) 1.34 (1.22 to 1.48) Location† Mostly working outside 1.48 (1.25 to 1.76) 1.51 (1.24 to 1.84) 1.41 (0.99 to 2.02) Working partly inside 1.16 (1.07 to 1.27) 1.17 (1.06 to 1.29) 1.14 (0.96 to 1.36) Working mostly inside 1.27 (1.21 to 1.33) 1.29 (1.22 to 1.36) 1.22 (1.11 to 1.33) Social distancing† Always maintained 1.11 (1.06 to 1.17) 1.13 (1.07 to 1.21) 1.06 (0.95 to 1.18) Not always 1.22 (1.15 to 1.29) 1.22 (1.14 to 1.30) 1.21 (1.09 to 1.36) Never maintained 1.51 (1.43 to 1.59) 1.54 (1.45 to 1.63) 1.43 (1.28 to 1.59)
• *Model adjusted for gender, age and geographic region.

• †Compared with homeworkers or working alone.