Univariate and adjusted analysis comparing participants who used medical masks and cloth masks*
| Univariate RR (95% CI) | Adjusted RR (95% CI) | |
|---|---|---|
| CRI | ||
| Medical mask (35/750, 4.67%) | Ref | Ref |
| Cloth mask (46/607, 7.58%) | 1.62 (1.06 to 2.49) | 1.51 (0.97 to 2.32) |
| Male | 0.60 (0.32 to 1.12) | 0.58 (0.31 to 1.08) |
| Vaccination | 0.66 (0.17 to 2.62) | 0.68 (0.17 to 2.67) |
| Hand washing | 0.81 (0.58 to 1.15) | 0.84 (0.59 to 1.20) |
| Compliance | 1.01 (1.00 to 1.03) | 1.01 (1.00 to 1.02) |
| ILI | ||
| Medical mask (2/750, 0.27%) | Ref | Ref |
| Cloth mask (13/607, 2.14%) | 8.03 (1.82 to 35.45) | 6.64 (1.45 to 28.65) |
| Male | 0.95 (0.27 to 3.35) | 0.92 (0.26 to 3.22) |
| Vaccination | 1.87 (0.25 to 13.92) | 1.97 (0.27 to 14.45) |
| Hand washing | 0.56 (0.24 to 1.27) | 0.61 (0.23 to 1.57) |
| Compliance | 1.04 (1.01 to 1.08) | 1.04 (1.00 to 1.08) |
| Laboratory-confirmed viruses | ||
| Medical mask (22/750, 2.93%) | Ref | Ref |
| Cloth mask (34/607, 5.60%) | 1.91 (1.13 to 3.23) | 1.72 (1.01 to 2.94) |
| Male | 0.64 (0.30 to 1.33) | 0.61 (0.29 to 1.27) |
| Vaccination | 0.97 (0.24 to 3.86) | 1.03 (0.26 to 4.08) |
| Hand washing | 0.61 (0.41 to 0.93) | 0.65 (0.42 to 1.00) |
| Compliance | 1.00 (0.99 to 1.02) | 1.0 (0.99 to 1.02) |
Bold typeface indicates statistically significant. *The majority (456/458) of HCWs in the control arm used a mask. Controls who exclusively used a medical mask were categorised and analysed with the medical mask arm participants; and controls who exclusively wore a cloth mask were categorised and analysed with the cloth mask arm.
CRI, clinical respiratory illness; HCWs, healthcare workers; ILI, influenza-like illness; RR, relative risk.