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Mask wearing to prevent secondary infection, transmission mostly within households, review of community use of face masks and similar barriers to prevent respiratory illness, 1 January 1980–19 June 2020
CI: confidence interval; M-H: Mantel–Haenszel; RCT: randomised controlled trial.
See Table 1 for study reference numbers, study setting, study design, outcome, comparison (when not allocated arms in RCTs) and any concurrent other intervention in both study arms.
