The effectiveness of medical face masks and respirators in reducing SARS-CoV-2 transmission in community settings: a scoping review

BackgroundDuring the COVID-19 pandemic, various public health and social measures (PHSM) were implemented with the primary objective of curtailing the transmission of SARS-CoV-2. This review aims to synthesise existing evidence on the effectiveness of medical facemasks and/or respirators (FFP2/KN95/N95) in reducing SARS-CoV-2 transmission/infection in community settings. MethodsA scoping literature review adhering to PRISMA was performed. All relevant study designs within community settings, excluding modelling studies, published between January 2000 and January 2023 and indexed in Medline and Embase were included with no geographical limitation. Studies not specifying facemask/respirator type or not presenting isolated outcomes for specific facemask/respirator types were excluded. ResultsOf the 10,185 studies identified, two randomised controlled trials (RCT) and two case-control studies met all inclusion criteria. The largest RCT identified an adjusted prevalence ratio of 0.89 (95%CI: 0.78-1.00) for medical vs. cloth masks. In a smaller RCT, the between-group difference favoured the mask vs no mask group (-0.3 percentage points; 95%CI: -1.2 to 0.4). Within one case-control study, N95/KN95 respirators (aOR 0.17; 95%CI: 0.05-0.64) or medical masks (aOR 0.34; 95%CI: 0.13-0.90) were associated with statistically significant lower adjusted odds of a positive test result compared to no facemask use. A second case-control study associated medical mask use with reduced COVID-19 risk in unadjusted models (OR 0.25; 95% CI: 0.12-0.53) but this effect was not independently associated with infection in multivariable models (aOR 0.61; 95%CI: 0.25-1.49). ConclusionsLimited published evidence exists on the effectiveness of medical facemask use in community settings. Medical masks and respirators (compared to cloth masks) may reduce SARS-CoV-2 transmission, but interpretation requires caution. Mask use in community settings was rarely implemented in isolation to other PHSMs so deciphering whether the effect is solely because of mask-wearing or a combined effect is extremely challenging necessitating additional studies.