The secondary outcomes were filtering capacity of masks and viral load reduction.

When her Danish colleagues first suggested distributing protective cloth face masks to individuals in Guinea-Bissau to stem the spread from the coronavirus, Christine Benn wasn’t so sure. We found minimal-certainty evidence that wearing a face mask is owned by decreased risk of primary infection in RCTs along with observational studies. However, the wide confidence intervals affected the statistical significance of the overall estimate. It was not possible to determine the certainty of evidence about mortality, filtering capacity and R0 whereas viral load was judged to get of suprisingly low quality.

Our findings indicate (i) an overall consensus toward a decrease in deaths, based on prediction modeling studies, in the event the population mask coverage is near-universal, irrespective of mask efficacy; (ii) filtration efficiency is dependent upon the breathing filter materials, with studies showing high variability. It seems that all sorts of masks decrease the viral exposure, even though the amounts of protection, regarding lowering of the likelihood of infection inside the wearer, are probably lower for many materials (i.e., cloth masks), on the extent that they can don’t effectively force away infectious aerosols. Specifically, personal respirators were more efficient than surgical masks, which are extremely effective than home-made masks; (iii) inside the worst-case scenario which has a mask efficacy at 30% and a population coverage at 20%, the R0 reduced from the initial valuation on 2.0 to only 1.9; whereas in the best-case scenario, when the mask efficacy is 95%, the R0 can fall to 0.99 from a preliminary value of 16.90, even though no population coverage nor time horizon is reported; (iv) wearing vs. not wearing a mask is associated with a lowering of viral load of RR 0.25 (95% CI 0.09–0.67, based on one experimental laboratory study).

face mask


A total of 684 records resulted in the searches within the electronic databases (MEDLINE, EMBASE, SCISEARCH) and from pre-prints; eleven additional records were identified through citations. After removing duplicates and excluding irrelevant records in accordance with title, abstract and full text reading, 35 studies met our inclusion criteria to the final inclusion. Figure 1 shows the flow diagram of the study buying process.