We reviewed this and related literature in detail in a pre-print: https://medium.com/@matthiassamwald/promoting-simple-do-it-yourself-masks-an-urgent-intervent

We reviewed this and related literature in detail in a pre-print: https://medium.com/@matthiassamwald/promoting-simple-do-it-yourself-masks-an-urgent-intervention-for-covid-19-mitigation-14da4100f429 https://medium.com/@matthiassamwald/promoting-simple-do-it-y... The upshot is, masks work, and the simple ones are particularly effective for protecting other people from transmission of infectious droplets from the person wearing the mask.