the number of ^reviews^ of the evidence on masks published in the last three months – fifteen to our knowledge. Yet, the number of published trials on the effects of masks in Covid-19 transmission is – so far – zero.
Prof.C.Heneghen in newspaper recently.
The review quoted above states
Cloth face coverings are effective in reducing source virus transmission, i.e., outward protection of others, when they are of ^optimal material and construction (high grade cotton, hybrid and multilayer) and fitted correctly ^ and for source protection of the wearer.
Also
2.1 Background and existing knowledge: health care settings of surgical masks and respirators.
Current knowledge on the
effectiveness of face masks to
prevent virus transmission from COVID-19, SARS, MERS and H1N1 is mostly limited to studies of surgical masks and N95 respirators. The
majority of existing studies are conducted in health care settings and focus on protection of the mask
wearer as opposed to wearing a mask for the protection of others. This distinction is vital since mask wearing for the general public occurs in non-clinical situations (home, public transport, shops, restaurants) and involves both protection of oneself but also others. Surgical masks and N95 respirators were included in the most recent systematic review and meta-analysis published in the Lancet. Based on 29 studies, the authors concluded that the use of both N95 respirators and surgical masks (including similar reusable masks) were associated with large reductions in virus
transmission. In this meta-analysis, they also found that mask wearing in non-health care settings is protective and statistically significant (RR=0.56, CI 0.40-0.79). There were, however, some concerns about this study including difficulty in separating effects of different types of PPE (masks, eye protection), potential confounders and the transferability of results to community settings. Another meta-analysis found that medical masks provided similar protection to N95 respirators in protecting against viral respiratory infections in healthcare settings. We emphasise that the majority of studies have been conducted in health care settings and there are therefore caveats in the ability to transfer results directly to community settings
Not much scientigic evidence there for Joe Public with their single layer masks that are not fitted to their faces properly.
Hell it even states on mask packets that this is a "fashion mask" and will not stop transmission of viruses."