Cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness.BMJ Open. 2016 12 30; 6(12):e012330.BO
RATIONALE
Medical masks are commonly used by sick individuals with influenza-like illness (ILI) to prevent spread of infections to others, but clinical efficacy data are absent.
OBJECTIVE
Determine whether medical mask use by sick individuals with ILI protects well contacts from related respiratory infections.
SETTING
6 major hospitals in 2 districts of Beijing, China.
DESIGN
Cluster randomised controlled trial.
PARTICIPANTS
245 index cases with ILI.
INTERVENTION
Index cases with ILI were randomly allocated to medical mask (n=123) and control arms (n=122). Since 43 index cases in the control arm also used a mask during the study period, an as-treated post hoc analysis was performed by comparing outcomes among household members of index cases who used a mask (mask group) with household members of index cases who did not use a mask (no-mask group).
MAIN OUTCOME MEASURE
Primary outcomes measured in household members were clinical respiratory illness, ILI and laboratory-confirmed viral respiratory infection.
RESULTS
In an intention-to-treat analysis, rates of clinical respiratory illness (relative risk (RR) 0.61, 95% CI 0.18 to 2.13), ILI (RR 0.32, 95% CI 0.03 to 3.13) and laboratory-confirmed viral infections (RR 0.97, 95% CI 0.06 to 15.54) were consistently lower in the mask arm compared with control, although not statistically significant. A post hoc comparison between the mask versus no-mask groups showed a protective effect against clinical respiratory illness, but not against ILI and laboratory-confirmed viral respiratory infections.
CONCLUSIONS
The study indicates a potential benefit of medical masks for source control, but is limited by small sample size and low secondary attack rates. Larger trials are needed to confirm efficacy of medical masks as source control.
TRIAL REGISTRATION NUMBER
ACTRN12613000852752; Results.