Leave it to Steve - he makes irrational statements, I post a link to answers, and he choses to misrepresent the papers in the results. Asking me to prove he's wrong, he's not interested in proving he's correct, he keeps pushing the same tired politically-motivated line.

Well, Maggie, you post sources without comment. I've perused some of them and they largely confirm what I've been saying about the evidence: that most of it is observational, that randomised control testing is not possible because of the ethical deficiency of having an "unprotected" control group. Making real-life extrapolations as to efficacy from laboratory testing of various types of masks is not justified.

BS. Just nonsense. A point made here says that the efficacy of masks can't be taken in isolation - you also need to consider social distancing and handwashing, etc, but given the severity of the pandemic, each is equally important. Here are some abstracts and highlights from the top few papers in that list that came out in 2021:


An evidence review of face masks against COVID-19 January 26, 2021    https://doi.org/10.1073/pnas.2014564118

Abstract
The science around the use of masks by the public to impede COVID-19 transmission is advancing rapidly. In this narrative review, we develop an analytical framework to examine mask usage, synthesizing the relevant literature to inform multiple areas: population impact, transmission characteristics, source control, wearer protection, sociological considerations, and implementation considerations. A primary route of transmission of COVID-19 is via respiratory particles, and it is known to be transmissible from presymptomatic, paucisymptomatic, and asymptomatic individuals. Reducing disease spread requires two things: limiting contacts of infected individuals via physical distancing and other measures and reducing the transmission probability per contact. 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. Because many respiratory particles become smaller due to evaporation, we recommend increasing focus on a previously overlooked aspect of mask usage: mask wearing by infectious people (“source control”) with benefits at the population level, rather than only mask wearing by susceptible people, such as health care workers, with focus on individual outcomes. We recommend that public officials and governments strongly encourage the use of widespread face masks in public, including the use of appropriate regulation.


Face masks against COVID-19: Standards, efficacy, testing and decontamination methods June 2021 https://doi.org/10.1016/j.cis.2021.102435

Highlights
• Universal face masking as a low-cost strategy to mitigate virus transmission

• Interdisciplinary systematic review on face masking against COVID-19

• Standards for various face masks and their fundamental filtration mechanisms

• Empirical methods for determining mask integrity and particle filtration efficiency

• Decontamination methods that allow for the reuse of traditionally disposable masks



Why does the spread of COVID-19 vary greatly in different countries? Revealing the efficacy of face masks in epidemic prevention   January 14, 2021   DOI: https://doi.org/10.1017/S0950268821000108

Abstract
The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) is highly contagious, and the coronavirus disease 2019 (COVID-19) pandemic caused by it has forced many countries to adopt ‘lockdown’ measures to prevent the spread of the epidemic through social isolation of citizens. Some countries proposed universal mask wearing as a protection measure of public health to strengthen national prevention efforts and to limit the wider spread of the epidemic. In order to reveal the epidemic prevention efficacy of masks, this paper systematically evaluates the experimental studies of various masks and filter materials, summarises the general characteristics of the filtration efficiency of isolation masks with particle size, and reveals the actual efficacy of masks by combining the volume distribution characteristics of human exhaled droplets with different particle sizes and the SARS-CoV-2 virus load of nasopharynx and throat swabs from patients. The existing measured data show that the filtration efficiency of all kinds of masks for large particles and extra-large droplets is close to 100%. From the perspective of filtering the total number of pathogens discharged in the environment and protecting vulnerable individuals from breathing live viruses, the mask has a higher protective effect. If considering the weighted average filtration efficiency with different particle sizes, the filtration efficiencies of the N95 mask and the ordinary mask are 99.4% and 98.5%, respectively. The mask can avoid releasing active viruses to the environment from the source of infection, thus maximising the protection of vulnerable individuals by reducing the probability of inhaling a virus. Therefore, if the whole society strictly implements the policy of publicly wearing masks, the risk of large-scale spread of the epidemic can be greatly reduced. Compared with the overall cost of social isolation, limited personal freedoms and forced suspension of economic activities, the inconvenience for citizens caused by wearing masks is perfectly acceptable.


This in particular helps because it has a good photo illustration of with and without masks, and types of masks:

Protection From COVID-19: The Efficacy of Face Masks February 5, 2021 doi: 10.3238/arztebl.m2021.0119

Abstract
Background
Since the beginning of 2020 the SARS-CoV-2 virus has spread to nearly every country in the world. The mainly airborne pathogen has led to large numbers of deaths, principally in elderly and vulnerable segments of the population. Protective vaccines have recently become available, but it is not yet clear whether and when population-wide immunity will be achieved. The existence of evidence for the protective effect of masks covering the mouth and nose is a topic of public debate.

Methods
A selective literature search was carried out in PubMed. Data from the German Robert Koch Institute and the Centers for Disease Control and Prevention were also taken into account.

Results
When talking, as many as 20 000 droplets ranging in size from 20 to 500 µM are released every second. According to PCR tests, the amount of virus exhaled is highest immediately before the onset of symptoms. No randomized trials have been conducted on the effect of masks covering the mouth and nose. A meta-analysis of 29 studies on infection with SARS-CoV-2, SARS, or MERS revealed that type N-95 masks (corresponding approximately to FFP-2), surgical masks, or similar multilayer cotton masks can greatly reduce the infection risk for the wearers (RR 0.34 [0.26; 0.45], with moderate heterogeneity [I2 = 48%]). Model experiments and case reports suggest that masks covering the mouth and nose afford considerable protection against transmission of SARS-CoV-2 and other airborne diseases by reducing release of and exposure to potentially infectious droplets; in addition, infections that do occur take a milder course. A limitation of the studies analyzed is that in most cases, this effect cannot be viewed in isolation from the protective impact of other measures (distancing, hygiene precautions).

Conclusion
It can plausibly be assumed that consistent use of masks covering the mouth and nose can play an important role in containing the spread of SARS-CoV-2.

Since the outbreak in Wuhan (China) in early 2020, SARS-CoV-2 has spread into a pandemic. The pathogen is mostly transmitted via the respiratory route. It has caused many deaths, especially in older and vulnerable populations. Vaccines have become available recently, but it is not known how quickly vaccinations will help to establish immunity at the population level (1). The most important protective measures against infection with SARS-CoV-2 include:

Adhering to safe minimum distances

Complying with hygiene measures, and

Wearing a face covering over nose and mouth (mask).