Table 1

Demographic and other characteristics of the index cases and household members

VariableMask arm (% and 95% CI)Control arm (% and 95% CI)
Index case (number)123122
 Gender (male)56/123
45.5% (37.0% to 54.3%)
45/122
36.9% (28.8% to 45.7%)
 Age (mean)40.2 (37.6 to 42.8)39.7 (37.3 to 42.0)
 Education (undergraduate/postgraduate)78/123
63.4% (54.6% to 71.4%)
74/122
60.7% (51.8% to 68.9%)
 Smoker (current/ex)29/123
23.6% (16.9% to 31.8%)
26/122
21.3% (15.0% to 29.4%)
 Pre-existing illness*21/123
17.1% (16.2% to 31.0%)
16/122
13.1% (8.2% to 20.2%)
 Influenza vaccination (yes)5/123
4.1% (1.7% to 9.2%)
5/122
4.1% (1.8% to 9.2%)
 Hand washing (most/all times)98/123
79.7% (71.7% to 85.8%)
109/122
89.3% (82.6% to 93.7%)
 Average hour of home stay†16.6 (15.9 to 17.3)16.6 (15.9 to 17.3)
 Average hour mask wearing†4.4 (3.9 to 4.9)1.4 (0.9 to 1.8)
Household (members)302295
 Number of household per arm2.52.4
 Gender (male)149/302
49.3% (43.4% to 24.6%)
168/295
56.9% (51.6% to 62.9%)
 Influenza vaccination (yes)‡22/298
7.4% (4.9% to 10.9%)
30/285
10.5% (7.1% to 14.6%)
 Age (mean)38.3 (36.0 to 40.5)36.4 (34.1 to 38.8)
  • *Includes asthma, chronic obstructive pulmonary disease, diabetes, ischaemic heart disease, immune-compromised and others.

  • †Variable was created by taking average hours over the trial period.

  • ‡Missing data for 14 cases.