roc Nat Acad Sci USA
2021 Jan 26;118(4)
An evidence review of face masks against COVID-19
Abstract
...The preponderance of evidence indicates that mask wearing reduces transmissibility per contact by reducing transmission of infected respiratory particles in both laboratory and clinical contexts. Public mask wearing is most effective at reducing spread of the virus when compliance is high. Given the current shortages of medical masks, we recommend the adoption of public cloth mask wearing, as an effective form of source control, in conjunction with existing hygiene, distancing, and contact tracing strategies.
You didn't read the whole study did you?
They also noted that, 'There are many important issues that need to be addressed. In this section, we suggest further research directions.'
The impact of using masks to control transmission in the workplace has not been well studied. One issue that impacts both school and work usage is that, over a full day’s use, masks may become wet, or dirty.
Notice the part where it states has not been well studied. Why? I would assume its a bit to early.
mSphere: 2020 Oct 21;5(5):e00637-20.
Effectiveness of Face Masks in Preventing Airborne Transmission of SARS-CoV-2
Abstract:
...We found that cotton masks, surgical masks, and N95 masks all have a protective effect with respect to the transmission of infective droplets/aerosols of SARS-CoV-2 and that the protective efficiency was higher when masks were worn by a virus spreader. Importantly, medical masks (surgical masks and even N95 masks) were not able to completely block the transmission of virus droplets/aerosols even when completely sealed. Our data will help medical workers understand the proper use and performance of masks and determine whether they need additional equipment to protect themselves from infected patients.IMPORTANCE Airborne simulation experiments showed that cotton masks, surgical masks, and N95 masks provide some protection from the transmission of infective SARS-CoV-2 droplets/aerosols; however, medical masks (surgical masks and even N95 masks) could not completely block the transmission of virus droplets/aerosols even when sealed.
This article may or may not have any updates. It's almost a year old, and as we know many opinions have changed on issues since that time.
The beginning part also notes that we don't have a full confirmation as of the date of this article.
Guidelines from the CDC and the WHO recommend the wearing of face masks to prevent the spread of coronavirus (CoV) disease 2019 (COVID-19); however, the protective efficiency of such masks against airborne transmission of infectious severe acute respiratory syndrome CoV-2 (SARS-CoV-2) droplets/aerosols is unknown.
This is all new science, and they are doing the best they can to find answers.
Meta-Analysis
Jul-Aug 2020;36
Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis
Abstract
Results: A total of 21 studies met our inclusion criteria. Meta-analyses suggest that mask use provided a significant protective effect (OR = 0.35 and 95% CI = 0.24-0.51). Use of masks by healthcare workers (HCWs) and non-healthcare workers (Non-HCWs) can reduce the risk of respiratory virus infection by 80% (OR = 0.20, 95% CI = 0.11-0.37) and 47% (OR = 0.53, 95% CI = 0.36-0.79). The protective effect of wearing masks in Asia (OR = 0.31) appeared to be higher than that of Western countries (OR = 0.45). Masks had a protective effect against influenza viruses (OR = 0.55), SARS (OR = 0.26), and SARS-CoV-2 (OR = 0.04). In the subgroups based on different study designs, protective effects of wearing mask were significant in cluster randomized trials and observational studies.
This study is more than a year old, and they also have a quote showing its NOT firm science yet.
Further improvements for original studies are needed in the future
Important knowledge gaps persist. At present, current evidence on the protective efficiency of masks among the general population is still insufficient. Only one study included in our meta-analysis investigated whether people with certain underlying conditions require masks or not [33]. Recall bias in case-control studies seems inevitable [22]. Therefore, high-quality and well-designed RCTs will be desired to investigate the actual protective effectiveness of masks.
Whereas, masks to me in certain circumstances are common sense. Yet, to say the science is settled? Even the science doesn't say that.
That's why I was wondering about the other parts of the world, and how they came to their conclusions of no mask mandates.
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