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Posted Oct 30, 2021, 8:05 PM
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Registered User
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Join Date: Dec 2016
Location: San Francisco
Posts: 24,177
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Originally Posted by someone123
I keep hearing about how great mask wearing is but few people address the data that's available, the differences in recommendations in different jurisdictions, or the effect that say vaccination or other measures might have on outcomes.
There have unfortunately not been many real-world high-quality (e.g. cluster randomized controlled) trials of masks. There was the Bangladesh study as one example and it showed the effect of cloth masks was down around the noise level while there were some narrow effects for surgical masks. This was in a completely unvaccinated population. Studies like this seem to have had no effect on the beliefs of most people; for example the staunch mask advocates for the most part still seem happy with cloth masks and they satisfy the mandates.
I'm not anti mask. In fact I would have preferred that mask wearing have a strong verifiable effect on reducing spread. Masks are really nothing like airbags or seatbelts. Seatbelts are much easier to study (collect data on traffic accidents and who was or wasn't wearing a seatbelt). Population-level viral transmission is much subtler than whether or not the occupants of a vehicle die in a crash. Even if a mask is 100% effective while you wear it, it may have no real-world impact if you have to take it off sometimes (like when eating in an indoor restaurant, something allowed in many places with mask mandates) and then you get infected.
This dynamic is at play with almost all of the covid interventions. There are lots of people yelling at each other over whether or not poorly understood measure X was a good pandemic response. The big shining exception is the vaccines, which have been well studied.
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A technical review of face mask wearing in preventing respiratory COVID-19 transmission
Abstract
Since the outbreak of the COVID-19 pandemic, most countries have recommended their citizens to adopt social distance, hand hygiene, and face mask wearing. However, wearing face masks has not been well adopted by many citizens. While the reasons are complex, there is a general perception that the evidence to support face mask wearing is lacking, especially for the general public in a community setting. Face mask wearing can block or filter airborne virus-carrying particles through the working of colloid and interface science. This paper assesses current knowledge behind the design and functioning of face masks by reviewing the selection of materials, mask specifications, relevant laboratory tests, and respiratory virus transmission trials, with an overview of future development of reusable masks for the general public. This review highlights the effectiveness of face mask wearing in the prevention of COVID-19 infection.
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https://www.sciencedirect.com/scienc...59029421000017
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An evidence review of face masks against COVID-19
Jeremy Howard, Austin Huang, et. al.
PNAS January 26, 2021 118 (4) e2014564118; https://doi.org/10.1073/pnas.2014564118
Edited by Lauren Ancel Meyers, The University of Texas at Austin, Austin, TX, and accepted by Editorial Board Member Nils C. Stenseth December 5, 2020 (received for review July 13, 2020)
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.
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https://www.pnas.org/content/118/4/e2014564118
https://jamanetwork.com/journals/jam...rticle/2776536
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Mask use in community settings in the context of COVID-19: A systematic review of ecological data
Nathan Ford, Haley K. Holmer et. al.
Published:July 18, 2021
DOI:https://doi.org/10.1016/j.eclinm.2021.101024
Abstract
Background
The wearing of medical and non-medical masks by the general public in community settings is one intervention that is important for the reduction of SARS-CoV-2 transmission, and has been the subject of considerable research, policy, advocacy and debate. Several observational studies have used ecological (population-level) data to assess the effect of masks on transmission, hospitalization, and mortality at the region or community level.
Methods
We undertook this systematic review to summarize the study designs, outcomes, and key quality indicators of using ecological data to evaluate the association between mask wearing and COVID-19 outcomes. We searched the World Health Organization (WHO) COVID-19 global literature database up to 5 March 2021 for studies reporting the impact of mask use in community settings on outcomes related to SARS-CoV-2 transmission using ecological data.
Findings
Twenty one articles were identified that analysed ecological data to assess the protective effect of policies mandating community mask wearing. All studies reported SARS-CoV-2 benefits in terms of reductions in either the incidence, hospitalization, or mortality, or a combination of these outcomes. Few studies assessed compliance to mask wearing policies or controlled for the possible influence of other preventive measures such as hand hygiene and physical distancing, and information about compliance to these policies was lacking.
Interpretation
Ecological studies have been cited as evidence to advocate for the adoption of universal masking policies. The studies summarized by this review suggest that community mask policies may reduce the population-level burden of SARS-CoV-2. Methodological limitations, in particular controlling for the actual practice of mask wearing and other preventive policies make it difficult to determine causality. There are several important limitations to consider for improving the validity of ecological data.
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https://www.thelancet.com/journals/e...304-7/fulltext
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