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 factorsInfluenza
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 day1.12 (1.06 to 1.18)1.14 (1.08 to 1.22)1.05 (0.95 to 1.17)
 10–30 per day1.32 (1.25 to 1.40)1.32 (1.24 to 1.41)1.31 (1.18 to 1.47)
 >30 per day1.40 (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 only1.12 (1.06 to 1.18)1.13 (1.06 to 1.20)1.08 (0.97 to 1.20)
 In workspaces with general public1.23 (1.17 to 1.30)1.25 (1.17 to 1.32)1.18 (1.06 to 1.31)
 Regular contacts with infected patients1.64 (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 outside1.48 (1.25 to 1.76)1.51 (1.24 to 1.84)1.41 (0.99 to 2.02)
 Working partly inside1.16 (1.07 to 1.27)1.17 (1.06 to 1.29)1.14 (0.96 to 1.36)
 Working mostly inside1.27 (1.21 to 1.33)1.29 (1.22 to 1.36)1.22 (1.11 to 1.33)
Social distancing†
 Always maintained1.11 (1.06 to 1.17)1.13 (1.07 to 1.21)1.06 (0.95 to 1.18)
 Not always1.22 (1.15 to 1.29)1.22 (1.14 to 1.30)1.21 (1.09 to 1.36)
 Never maintained1.51 (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.