“We Did Not Find Evidence that Surgical-Type Face Masks Are Effective…”
The following excerpt is from a May 2020 study that was published at ncbi.nlm.nih.gov:
Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures
“Hand hygiene is a widely used intervention and has been shown to effectively reduce the transmission of gastrointestinal infections and respiratory infections (26). However, in our systematic review, updating the findings of Wong et al. (8), we did not find evidence of a major effect of hand hygiene on laboratory-confirmed influenza virus transmission (Figure 1). Nevertheless, hand hygiene might be included in influenza pandemic plans as part of general hygiene and infection prevention.
We did not find evidence that surgical-type face masks are effective in reducing laboratory-confirmed influenza transmission, either when worn by infected persons (source control) or by persons in the general community to reduce their susceptibility (Figure 2). […]”
Although the study concerns an influenza virus, the flu, the same study might as well have been focused on corona viruses. It would still have produced the same results and conclusions. There’s no reason, whatsoever, to assume otherwise.