"Methods
Population description, eligibility and enrollment: We conducted a cluster-randomized controlled trial in which households were randomly allocated to a surgical mask arm (intervention) or a control (non-intervention) arm. The mask had to be worn by the index case only. The intervention was targeted at the household level, and the outcomes were measured at the individual level in household subjects...
Intervention: … The main objective was to assess the decrease of secondary [influenza-like] illness in household contact in the mask group vs. the control group. We also focused on the tolerance and feasibility of wearing masks...
Discussion
We did not show any significant difference in ILI [influenza-like illness] proportion among household contacts between the intervention arm and the control arm...
… Our findings [suggest] a low effectiveness, if any, of facemasks when used alone to limit influenza transmission in a closed-setting."
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