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Swiss Policy Research - Are Face Masks Effective?  The Evidence   

Special thanks to Swiss Policy Research for collating this data. 

Their website is here - https://swprs.org/face-masks-evidence/

Donations to SWPRS.ORG - https://swprs.org/donations/

Archive - https://archive.is/Awo5X


Cloth face masks in the general population might be effective, at least in some circumstances, but there is currently little to no evidence supporting this proposition. If the coronavirus is indeed transmitted via indoor aerosols, cloth masks are unlikely to be protective. Health authorities should therefore not assume or suggest that cloth face masks will reduce the rate or risk of infection.



 Studies on the effectiveness of face masks

So far, most studies found little to no evidence for the effectiveness of cloth face masks in the general population, neither as personal protective equipment nor as a source control.

  1. A May 2020 meta-study on pandemic influenza published by the US CDC found that face masks had no effect, neither as personal protective equipment nor as a source control. ¹
  2. A Danish randomized controlled trial with 6000 participants, published in the Annals of Internal Medicine in November 2020, found no statistically significant effect of high-quality medical face masks against SARS-CoV-2 infection in a community setting.²
  3. A large randomized controlled trial with close to 8000 participants, published in October 2020 in PLOS One, found that face masks “did not seem to be effective against laboratory-confirmed viral respiratory infections nor against clinical respiratory infection.” ³
  4. A February 2021 review by the European CDC found no significant evidence supporting the effectiveness of non-medical and medical face masks in the community. Furthermore, the European CDC advised against the use of FFP2/N95 masks by the general public.⁴
  5. A July 2020 review by the Oxford Centre for Evidence-Based Medicine found that there is no evidence for the effectiveness of cloth masks against virus infection or transmission.⁵
  6. A November 2020 Cochrane review found that face masks did not reduce influenza-like illness (ILI) cases, neither in the general population nor in health care workers.⁶
  7. An April 2020 review by two US professors in respiratory and infectious disease from the University of Illinois concluded that face masks have no effect in everyday life, neither as self-protection nor to protect third parties (so-called source control).⁷
  8. An article in the New England Journal of Medicine from May 2020 came to the conclusion that cloth face masks offer little to no protection in everyday life.⁸
  9. A 2015 study in the British Medical Journal BMJ Open found that cloth masks were penetrated by 97% of particles and may increase infection risk by retaining moisture or repeated use.⁹
  10. An August 2020 review by a German professor in virology, epidemiology and hygiene found that there is no evidence for the effectiveness of cloth face masks and that the improper daily use of masks by the public may in fact lead to an increase in infections. ¹⁰

[1] https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

Archive - https://archive.is/PTi7D

[2] https://www.acpjournals.org/doi/10.7326/M20-6817

Archive - https://archive.is/Tajg9

[3] https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0240287

Archive - https://archive.is/WpzAI

[4] https://www.ecdc.europa.eu/sites/default/files/documents/covid-19-face-masks-community-first-update.pdf

Archive - https://hexagod.net/pdfs/archive/covid-19-face-masks-community-first-update.pdf

[5] https://www.cebm.net/covid-19/masking-lack-of-evidence-with-politics/

Archive - https://archive.is/36jag

[6] https://www.cochrane.org/CD006207/ARI_do-physical-measures-such-hand-washing-or-wearing-masks-stop-or-slow-down-spread-respiratory-viruses

Archive - https://archive.is/Ipmdd

[7] https://www.cidrap.umn.edu/news-perspective/2020/04/commentary-masks-all-covid-19-not-based-sound-data

Archive - https://archive.is/nrc6c

[8] https://www.nejm.org/doi/full/10.1056/NEJMp2006372

Archive - https://archive.is/sXfd1

[9] https://bmjopen.bmj.com/content/5/4/e006577

Archive - https://archive.is/rdlpp

[10] https://www.thieme-connect.com/products/ejournals/html/10.1055/a-1174-6591

Archive - https://archive.is/kS1NH



Development of cases after mask mandates

In many states, coronavirus infections strongly increased after mask mandates had been introduced. The following charts show the typical examples of Austria, Belgium, France, Germany, Ireland, Italy, Spain, the UK, California and Hawaii. Furthermore, a direct comparison between US states with and without mask mandates indicates that mask mandates have made no difference.

Mask mandates and coronavirus infections (Source: Yinon Weiss)

Link - https://twitter.com/yinonw/status/1321177359601393664

Archive - https://archive.is/1CvdU


Effectiveness of N95/FFP2 mask mandates

In January 2021, the German state of Bavaria was one of the first places in the world to mandate N95/FFP2 masks in most public settings. A comparison with other German states, which required cloth or medical masks, indicates that N95/FFP2 masks made no difference.

"Covid" (the flu19) cases in Bavaria (FFP2/N95 mandate) vs. Germany overall (ARD/RKI/DaFeid)

Link - https://www.tagesschau.de/inland/coronavirus-karte-deutschland-101.html

Archive - https://archive.is/aHGAJ


Additional aspects
  1. There is increasing evidence¹ that the novel coronavirus is transmitted, at least in indoor settings, not only by droplets but also by smaller aerosols. However, due to their large pore size and poor fit, cloth masks cannot filter out aerosols (see video analysis below): over 90% of aerosols penetrate or bypass² the mask and fill a medium-sized room within minutes.
  2. The WHO admitted to the BBC that its June 2020 mask policy update³ was due not to new evidence but “political lobbying”⁴: “We had been told by various sources WHO committee reviewing the evidence had not backed masks but they recommended them due to political lobbying. This point was put to WHO who did not deny.” (D. Cohen, BBC Medical Corresponent).
  3. To date, the only randomized controlled trial (RCT) on face masks against SARS-CoV-2 infection in a community setting found no statistically significant benefit (see above). However, three major journals refused to publish⁵ this study, delaying its publication by several months.
  4. An analysis by the US CDC found that 85% of people⁶ infected with the new coronavirus reported wearing a mask “always” (70.6%) or “often” (14.4%). Compared to the control group of uninfected people, always wearing a mask did not reduce the risk of infection.
  5. Researchers from the University of Minnesota found that the infectious dose of SARS-CoV-2 is just 300 virions (virus particles), whereas a single minute of normal speaking may generate more than 750,000 virions⁷, making cloth face masks unlikely to prevent an infection.
  6. Japan, despite its widespread use of face masks, experienced its most recent influenza epidemic⁸ with more than 5 million people falling ill just one year ago, in January and February 2019. However, unlike SARS-CoV-2, the influenza virus is easily transmitted by children, too.
  7. In the US state of Kansas, the 90 counties without mask mandates had lower coronavirus infection rates than the 15 counties with mask mandates. To hide this fact, the Kansas health department tried to manipulate⁹ the official statistics and data presentation.
  8. Contrary to common belief, studies in hospitals found that¹⁰ the wearing of a medical mask by surgeons during operations didn’t reduce post-operative bacterial wound infections in patients.
  9. During the notorious 1918 influenza pandemic, the use of cloth face masks among the general population was widespread and in some places mandatory, but they made no difference¹¹.
  10. Asian countries with low covid infection rates, most of them neighboring China, benefited not from face masks but mainly from early border closures¹². This is confirmed by Scandinavian countries Norway, Finland and Denmark, which didn’t introduce mask mandates but closed borders early¹³ and saw very low covid infection and death rates, too.

[1] https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa939/5867798

Archive - https://archive.is/oyXHl

[2] https://bmjopen.bmj.com/content/5/4/e006577

Archive - https://archive.is/rdlpp

[3] https://swprs.org/who-mask-study-seriously-flawed/

Archive - https://archive.is/sgFEm

[4] https://twitter.com/deb_cohen/status/1282244773030633473

Archive - https://archive.is/YVJ0Y

[5] https://swprs.org/the-suppressed-danish-mask-study/

Archive - https://archive.is/7BEic

[6] https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6936a5-H.pdf#page=4

Archive - https://hexagod.net/pdfs/archive/mm6936a5-H.pdf

[7] https://www.nejm.org/doi/full/10.1056/NEJMc2030886

Archive - https://archive.is/8PSdy

[8] https://www.upi.com/Top_News/World-News/2019/02/01/Millions-in-Japan-affected-as-flu-outbreak-grips-country/9191549043797/

Archive - https://archive.is/MfFvo

[9] https://sentinelksmo.org/more-deception-kdhe-hid-data-to-justify-mask-mandate/

Archive - https://archive.is/quIGh

[10] https://link.springer.com/article/10.1007/BF01658736

Archive - https://archive.is/ALysm

[11] https://www.washingtonpost.com/history/2020/04/02/everyone-wore-masks-during-1918-flu-pandemic-they-were-useless/

Archive - https://archive.is/sD6Nb

[12] https://swprs.org/the-zero-covid-countries/

Archive - https://archive.is/41A0Z

[13] https://www.forbes.com/sites/davidnikel/2020/05/08/denmark-norway-relax-coronavirus-restrictions-but-borders-remain-closed/

Archive - https://archive.is/uXxdn


Risks associated with face masks

Wearing masks for a prolonged period of time is not harmless, as the following evidence shows:

  1. The WHO warns of various “side effects”¹ such as difficulty breathing and skin rashes.
  2. Tests conducted by the University Hospital of Leipzig in Germany have shown that² face masks significantly reduce the resilience and performance of healthy adults.
  3. A German psychological study with about 1000 participants found “severe psychosocial consequences”³ due to the introduction of mandatory face masks in Germany.
  4. The Hamburg Environmental Institute warned of the inhalation of chlorine compounds⁴ in polyester masks as well as problems in connection with face mask disposal.
  5. The European rapid alert system RAPEX has already recalled 70 mask models⁵ because they did not meet EU quality standards and could lead to “serious risks”.
  6. In Germany, two 13-year-old children died suddenly⁶ while wearing a mask⁷ for a prolonged period of time; autopsies couldn’t exclude CO2 intoxication⁸ or a sudden cardiac arrest.
  7. In China, several children who had to wear a mask during sports classes fainted and died⁹; the autopsies found a sudden cardiac arrest as the probable cause of death.
  8. In the US, a car driver wearing an N95 (FFP2) mask fainted and crashed¹⁰ into a pole.

[1] https://www.who.int/publications/i/item/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak

Archive - https://archive.is/zJqMq

[2] https://science.orf.at/stories/3201213/

Archive - https://archive.is/YrXXS

[3] https://corona-transition.org/der-maskenzwang-ist-verantwortlich-fur-schwere-psychische-schaden-und-die

Archive - https://archive.is/uV7FY

[4] https://corona-transition.org/maskentragen-noch-ungesunder-als-gedacht

Archive - https://archive.is/72YpB

[5] https://corona-transition.org/maskentragen-noch-ungesunder-als-gedacht

Archive - https://archive.is/72YpB

[6] https://corona-transition.org/13-jahrige-maskentragerin-stirbt

Archive - https://archive.is/CDQd1

[7] https://corona-transition.org/zweites-kind-wegen-maskentragen-gestorben

Archive - https://archive.is/CDQd1

[8] https://www.thoughtco.com/carbon-dioxide-poisoning-608396

Archive - https://archive.is/Tkqo7

[9] https://www.thatsmags.com/china/post/31100/student-deaths-lead-schools-to-adjust-rules-on-masks-while-exercising

Archive - https://archive.is/UZyQ4

[10] https://nypost.com/2020/04/24/driver-crashes-car-after-passing-out-from-wearing-n95-mask/

Archive - https://archive.is/aFquN

======== (Moved to end because face diapers do nothing other than kill you) ======

 Studies claiming face masks are effective

Some recent studies argued that cloth face masks are indeed effective against the (flu19) "new" coronavirus and could at least prevent the infection of other people. However, most of these studies suffer from poor methodology and sometimes show the opposite of what they claim to show.

Typically, these studies ignore the effect of other measures, the natural development of infection rates, changes in test activity, or they compare places with different epidemiological conditions. Studies performed in a lab or as a computer simulation often aren’t applicable to the real world.

An overview:

  1. A meta-study in the journal Lancet, commissioned by the WHO, claimed that masks “could” lead to a reduction in the risk of infection, but the studies considered mainly N95 respirators in a hospital setting, not cloth masks in a community setting, the strength of the evidence was reported as “low”, and experts found numerous flaws in the study. Professor Peter Jueni, epidemiologist at the University of Toronto, called the WHO study “essentially useless”.
  2. A study in the journal PNAS claimed that masks had led to a decrease in infections in three global hotspots (including New York City), but the study did not take into account the natural decrease in infections and other simultaneous measures. The study was so flawed that over 40 scientists recommended that the study be withdrawn.
  3. A US study claimed that US counties with mask mandates had lower Covid infection and hospitalization rates, but the authors had to withdraw their study as infections and hospitalizations increased in many of these counties shortly after the study was published.
  4. A German study claimed that the introduction of mandatory face masks in German cities had led to a decrease in infections. But the data does not support this claim: in some cities there was no change, in others a decrease, in others an increase in infections (see graph below). The city of Jena was an ‘exception’ only because it simultaneously introduced the strictest quarantine rules in Germany, but the study did not mention this.
  5. A Canadian study claimed that countries with mandatory masks had fewer deaths than countries without mandatory masks. But the study compared African, Latin American, Asian and Eastern European countries with very different infection rates and population structures.
  6. A review by the University of Oxford claimed that face masks are effective, but it was based on studies about SARS-1 and in health care settings, not in community settings.
  7. A review by members of the lobby group ‘Masks for All’, published in the journal PNAS, claimed that masks are effective as a source control against aerosol transmission in the community, but the review provided no real-world evidence supporting this proposition.

Go to https://swprs.org/face-masks-evidence/ to get these studies.

It's not worth the editor's time to bother getting these sources when we've evolved for over 100,000 years to not need a face diaper for our immune systems to work.


Another collation of mask studies (see also) - https://hexagod.net/masks_detail_studies.html

For the hyperlinks in this paper - https://hexagod.net/masks_swprs.html

Easy print pdf version

Face Mask Information


Editor's foreword:

Although it is always possible to avoid them, face masks are "mandatory" in many areas.  Interestingly enough, humans have evolved for hundreds of thousands of years to have completely smooth breathing paths.  Note that no mammal has fur inside its mouth.  Almost every living breathing (o2 exchanging) animal has a clear breathing path.

Therefore, it stands to reason that breathing obstructions are likely dangerous, harmful, and antithetical to our overall pattern of evolution.  One might respond that we have also evolved to not have fur, but that is not essential either, unless the human is in a very cold climate.  Even in animals that have fur, it notably stops around the mouth.

How have humans evolved for hundreds of thousands (if not millions) of years to not need masks?  If they were essential for our biological immune system, then why were they not required sooner?  Remember that even clothes are not essential, and they also act as optional and modular depending on the climate and social requirements.  Most mammals do have fur; it just varies depending on the average temperature of their environment, and it never obstructs their breathing.

Also, a large part of human communication is conveyed through non-verbal facial cues.  An example of this would be a response of a smile or a frown, and the even more subtle facial expression responses while communicating with other humans.



5 NIH/National Library of Medicine studies from 2004-2020 all finding verifiable health effects from wearing a face mask, including scientifically verified reduction is blood oxygen level:


Effect of a surgical mask on six minute walking distance

"Dyspnea variation was significantly higher with surgical mask (+5.6 vs. +4.6; P<0.001) and the difference was clinically relevant."

[EDITOR'S NOTE: Dyspnea is 'shortness of breath' or a person having trouble breathing]

Link - https://pubmed.ncbi.nlm.nih.gov/29395560/
Archive - https://archive.is/Y7wwb#selection-2221.62-2221.193


Exercise with facemask; Are we handling a devil's sword?

"Further contrary to the earlier thought, no evidence exists to claim the facemasks during exercise offer additional protection from the droplet transfer of the virus. "

Link - https://pubmed.ncbi.nlm.nih.gov/32590322/
Archive - https://archive.is/bWbIR#selection-2181.1049-2181.1216


The physiological impact of wearing an N95 mask during hemodialysis as a precaution against SARS in patients with end-stage renal disease

"Wearing an N95 mask for 4 hours during HD significantly reduced PaO2 and increased respiratory adverse effects in ESRD patients. "

Link - https://pubmed.ncbi.nlm.nih.gov/15340662/
Archive - https://archive.is/Nlwkc#selection-2085.14-2085.147


Respiratory consequences of N95-type Mask usage in pregnant healthcare workers-a controlled clinical study

" Breathing through N95 mask materials have been shown to impede gaseous exchange and impose an additional workload on the metabolic system of pregnant healthcare workers, and this needs to be taken into consideration in guidelines for respirator use. "

Link - https://pubmed.ncbi.nlm.nih.gov/26579222/
Archive - https://archive.is/Kdxh7#selection-2589.23-2591.264


Contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers

"Respiratory pathogens on the outer surface of the used medical masks may result in self-contamination."

Link - https://pubmed.ncbi.nlm.nih.gov/31159777/
Archive - https://archive.is/W2cuN


A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

"This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally."

Link - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/
Archive - https://archive.is/MHIFH


Facemasks and similar barriers to prevent respiratory illness such as COVID-19: A rapid systematic review

"The evidence is not sufficiently strong to support widespread use of facemasks as a protective measure against COVID-19."

Link - https://www.medrxiv.org/content/10.1101/2020.04.01.20049528v1
Archive - https://archive.is/OpVAB


Physical interventions to interrupt or reduce the spread of respiratory viruses. Part 1 - Face masks, eye protection and person distancing: systematic review and meta-analysis

"Compared to no masks there was no reduction of influenza-like illness (ILI) cases (Risk Ratio 0.93, 95%CI 0.83 to 1.05) or influenza (Risk Ratio 0.84, 95%CI 0.61-1.17) for masks in the general population, nor in healthcare workers (Risk Ratio 0.37, 95%CI 0.05 to 2.50). "

Link - https://www.medrxiv.org/content/10.1101/2020.03.30.20047217v2
Archive - https://archive.is/3jUOF#selection-1339.1292-1339.1562


Universal Masking in Hospitals in the Covid-19 Era

"We know that wearing a mask outside health care facilities offers little, if any, protection from infection."

Link - https://www.nejm.org/doi/full/10.1056/NEJMp2006372
Archive - https://archive.is/sXfd1


N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care PersonnelA Randomized Clinical Trial

Question  Is the use of N95 respirators or medical masks more effective in preventing influenza infection among outpatient health care personnel in close contact with patients with suspected respiratory illness?

Findings  In this pragmatic, cluster randomized clinical trial involving 2862 health care personnel, there was no significant difference in the incidence of laboratory-confirmed influenza among health care personnel with the use of N95 respirators (8.2%) vs medical masks (7.2%).

Meaning  As worn by health care personnel in this trial, use of N95 respirators, compared with medical masks, in the outpatient setting resulted in no significant difference in the rates of laboratory-confirmed influenza.

Link - https://jamanetwork.com/journals/jama/fullarticle/2749214
Archive - https://archive.is/KYAba


Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis

Background: Conflicting recommendations exist related to which facial protection should be used by health care workers to prevent transmission of acute respiratory infections, including pandemic influenza. We performed a systematic review of both clinical and surrogate exposure data comparing N95 respirators and surgical masks for the prevention of transmissible acute respiratory infections.

Methods: We searched various electronic databases and the grey literature for relevant studies published from January 1990 to December 2014. Randomized controlled trials (RCTs), cohort studies and case–control studies that included data on health care workers wearing N95 respirators and surgical masks to prevent acute respiratory infections were included in the meta-analysis.

Results: We identified 6 clinical studies (3 RCTs, 1 cohort study and 2 case–control studies) and 23 surrogate exposure studies. In the meta-analysis of the clinical studies, we found no significant difference between N95 respirators and surgical masks in associated risk of (a) laboratory-confirmed respiratory infection (RCTs: odds ratio [OR] 0.89, 95% confidence interval [CI] 0.64–1.24; cohort study: OR 0.43, 95% CI 0.03–6.41; case–control studies: OR 0.91, 95% CI 0.25–3.36); (b) influenza-like illness (RCTs: OR 0.51, 95% CI 0.19–1.41); or (c) reported workplace absenteeism (RCT: OR 0.92, 95% CI 0.57–1.50).

- https://www.cmaj.ca/content/188/8/567 -


The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence

None of the studies we reviewed established a conclusive relationship between mask/respirator use and protection against influenza infection.

Link - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/
Archive - https://archive.is/TDeD4


Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: a randomized controlled trial

Background: Health care workers outside surgical suites in Asia use surgical-type face masks commonly. Prevention of upper respiratory infection is one reason given, although evidence of effectiveness is lacking.

Methods: Health care workers in a tertiary care hospital in Japan were randomized into 2 groups: 1 that wore face masks and 1 that did not. They provided information about demographics, health habits, and quality of life. Participants recorded symptoms daily for 77 consecutive days, starting in January 2008. Presence of a cold was determined based on a previously validated measure of self-reported symptoms. The number of colds between groups was compared, as were risk factors for experiencing cold symptoms.

Results: Thirty-two health care workers completed the study, resulting in 2464 subject days. There were 2 colds during this time period, 1 in each group. Of the 8 symptoms recorded daily, subjects in the mask group were significantly more likely to experience headache during the study period (P < .05). Subjects living with children were more likely to have high cold severity scores over the course of the study.

Conclusion: Face mask use in health care workers has not been demonstrated to provide benefit in terms of cold symptoms or getting colds. A larger study is needed to definitively establish noninferiority of no mask use.

Link - https://pubmed.ncbi.nlm.nih.gov/19216002/
Archive - https://archive.is/1Hzxa


Comparison of Filtration Efficiency and Pressure Drop in Anti-Yellow Sand Masks, Quarantine Masks, Medical Masks, General Masks, and Handkerchiefs

Medical  masks  show  no  significant  differences  in  penetration and pressure drop between inward tests (which mimic   inhalation)   and   outward   tests   (which   mimic   exhalation).  General  masks  and  handkerchiefs  have  no  protection function in terms of the aerosol filtration efficiency.

[EDITOR'S NOTE: Aerosol droplets are how respiratory viruses spread]

Link - https://aaqr.org/articles/aaqr-13-06-oa-0201.pdf
Archive - https://hexagod.net/pdfs/archive/aaqr-13-06-oa-0201.pdf


A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.

Link - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/
Archive - https://archive.is/MHIFH


Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis supports the use of respiratory protection. However, the existing evidence is sparse and findings are inconsistent within and across studies.

Link - https://academic.oup.com/cid/article/65/11/1934/4068747
Archive - https://archive.is/NghAW


Comparison of the Filter Efficiency of Medical Nonwoven Fabrics against Three Different Microbe Aerosols

In  this  study,  we  compared  the  filter  efficiencies  of medical  nonwoven  fabrics  using  aerosols  containing three  test  microbes:  the  phi-X174  phage,  influenza virus, and S. aureus. Among the three types of spherical microbe  particles,  the  filter  efficiency  against  influenza virus  particles (particle  diameter  of  approximately  120 nm  determined  by  DLS)  was  the  lowest,  and  that against  the  phi-X174  phage (approximately  28  nm)was  the  highest  for  both  sample  1  and  2.  These find-ings suggest that the result of filter efficiency tests using the phi-X174 phage could be overestimated, compared with the filter efficiency against real pathogens such as the  influenza  virus.

Link - https://www.jstage.jst.go.jp/article/bio/23/2/23_61/_pdf/-char/en
Archive - https://archive.is/ejDNN


Postoperative wound infections and surgical face masks: A controlled study

It has never been shown that wearing surgical face masks decreases postoperative wound infections. On the contrary, a 50% decrease has been reported after omitting face masks. The present study was designed to reveal any 30% or greater difference in general surgery wound infection rates by using face masks or not.

Link - https://link.springer.com/article/10.1007/BF01658736
Archive - https://archive.is/ALysm


Surgical face masks in modern operating rooms—a costly and unnecessary ritual?

Following the commissioning of a new suite of operating rooms air movement studies showed a flow of air away from the operating table towards the periphery of the room. Oral microbial flora dispersed by unmasked male and female volunteers standing one metre from the table failed to contaminate exposed settle plates placed on the table. The wearing of face masks by non-scrubbed staff working in an operating room with forced ventilation seems to be unnecessary.

Link - https://www.journalofhospitalinfection.com/article/0195-6701(91)90148-2/pdf -
Archive - https://archive.is/59aMo


Is a Mask Necessary in the Operating Theatre [Editor's note: 'operating theatre' refers to the operating room for surgery on patients]

Summary: No masks were worn in one operating theatre for 6 months.  There was no increase in the evidence of wound infection.

Link - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2493952/pdf/annrcse01509-0009.pdf
Archive - https://web.archive.org/web/20200717141836/
|| hexagod.net/pdfs/archive/annrcse01509-0009.pdf

Rapid Expert Consultation on the Effectiveness of Fabric Masks for the COVID-19 Pandemic (April 8, 2020)

The aim of this rapid expert consultation is to respond to your request concerning the effectiveness of homemade fabric masks worn by the general public to protect others, as distinct from protecting the wearer. The request stems from an interest in reducing transmission within the community by individuals who are infected, potentially contagious, but asymptomatic. Overall, the available evidence is inconclusive about the degree to which homemade fabric masks may suppress the spread of infection from the wearer to others.

Bae et al. (2020) evaluated the effectiveness of surgical and cotton masks in filtering SARSCoV-2.10 They found that neither kind of mask reduced the dissemination of SARS-CoV-2 from the coughs of four symptomatic patients with COVID-19 to the environment and external mask surface.

Link - https://www.nap.edu/catalog/25776/rapid-expert-consultation-on-the-effectiveness-of-fabric-masks-for-the-covid-19-pandemic-
Archive - https://archive.is/kRDQB


Rapid Expert Consultation on the Effectiveness of Fabric Masks for the COVID-19 Pandemic

No public data available

Link - https://www.nap.edu/read/25776/chapter/1#6
Archive - https://archive.is/mWXRZ


Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures

Methods and Results
We conducted systematic reviews to evaluate the effectiveness of personal protective measures on influenza virus transmission, including hand hygiene, respiratory etiquette, and face masks, and a systematic review of surface and object cleaning as an environmental measure (Table 1). We searched 4 databases (Medline, PubMed, EMBASE, and CENTRAL) for literature in all languages.

Thumbnail of Meta-analysis of risk ratios for the effect of face mask use with or without enhanced hand hygiene on laboratory-confirmed influenza from 10 randomized controlled trials with &gt;6,500 participants. A) Face mask use alone; B) face mask and hand hygiene; C) face mask with or without hand hygiene. Pooled estimates were not made if there was high heterogeneity (I2 &gt;75%). Squares indicate risk ratio for each of the included studies, horizontal lines indicate 95% CIs, dashed vertical
Figure 2. Meta-analysis of risk ratios for the effect of face mask use with or without enhanced hand hygiene on laboratory-confirmed influenza from 10 randomized controlled trials with >6,500 participants. A) Face mask...
In our systematic review, we identified 10 RCTs that reported estimates of the effectiveness of face masks in reducing laboratory-confirmed influenza virus infections in the community from literature published during 1946–July 27, 2018. In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks

Link - https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article
Archive - https://archive.is/PTi7D


Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles

A shortage of disposable filtering facepiece respirators can be expected during a pandemic respiratory infection such as influenza A. Some individuals may want to use common fabric materials for respiratory protection because of shortage or affordability reasons. To address the filtration performance of common fabric materials against nano-size particles including viruses, five major categories of fabric materials including sweatshirts, T-shirts, towels, scarves, and cloth masks were tested for polydisperse and monodisperse aerosols (20–1000 nm) at two different face velocities (5.5 and 16.5 cm s−1) and compared with the penetration levels for N95 respirator filter media.

The results showed that cloth masks and other fabric materials tested in the study had 40–90% instantaneous penetration levels

Link - https://academic.oup.com/annweh/article/54/7/789/202744
Archive -


Optical microscopic study of surface morphology and filtering efficiency of face masks

Low-cost face masks made from different cloth materials are very common in developing countries. The cloth masks (CM) are usually double layered with stretchable ear loops. It is common practice to use such masks for months after multiple washing and drying cycles. If a CM is used for long time, the ear loops become stretched. The loop needs to be knotted to make the mask loop fit better on the face. It is not clear how washing and drying and stretching practices change the quality of a CM. The particulate matter (PM) filtering efficiency of a mask depends on multiple parameters, such as pore size, shape, clearance, and pore number density. It is important to understand the effect of these parameters on the filtering efficiency.

We characterized the surface of twenty different types of CMs using optical image analysis method. The filtering efficiency of selected cloth face masks was measured using the particle counting method. We also studied the effects of washing and drying and stretching on the quality of a mask.

The pore size of masks ranged from 80 to 500 μm, which was much bigger than particular matter having diameter of 2.5 μm or less (PM2.5) and 10 μm or less (PM10) size. The PM10 filtering efficiency of four of the selected masks ranged from 63% to 84%. The poor filtering efficiency may have arisen from larger and open pores present in the masks. Interestingly, we found that efficiency dropped by 20% after the 4th washing and drying cycle. We observed a change in pore size and shape and a decrease in microfibers within the pores after washing. Stretching of CM surface also altered the pore size and potentially decreased the filtering efficiency. As compared to CMs, the less frequently used surgical/paper masks had complicated networks of fibers and much smaller pores in multiple layers in comparison to CMs, and therefore had better filtering efficiency. This study showed that the filtering efficiency of cloth face masks were relatively lower, and washing and drying practices deteriorated the efficiency. We believe that the findings of this study will be very helpful for increasing public awareness and help governmental agencies to make proper guidelines and policies for use of face mask.

Link - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599448/
Archive - https://archive.is/21bKj


Effectiveness of Surgical and Cotton Masks in Blocking SARS–CoV-2: A Controlled Comparison in 4 Patients

Methods and Findings: The institutional review boards of 2 hospitals in Seoul, South Korea, approved the protocol, and we invited patients with COVID-19 to participate. After providing informed consent, patients were admitted to negative pressure isolation rooms. We compared disposable surgical masks (180 mm × 90 mm, 3 layers [inner surface mixed with polypropylene and polyethylene, polypropylene filter, and polypropylene outer surface], pleated, bulk packaged in cardboard; KM Dental Mask, KM Healthcare Corp) with reusable 100% cotton masks (160 mm × 135 mm, 2 layers, individually packaged in plastic; Seoulsa).
A petri dish (90 mm × 15 mm) containing 1 mL of viral transport media (sterile phosphate-buffered saline with bovine serum albumin, 0.1%; penicillin, 10 000 U/mL; streptomycin, 10 mg; and amphotericin B, 25 µg) was placed approximately 20 cm from the patients' mouths. Patients were instructed to cough 5 times each onto a petri dish while wearing the following sequence of masks: no mask, surgical mask, cotton mask, and again with no mask. A separate petri dish was used for each of the 5 coughing episodes. Mask surfaces were swabbed with aseptic Dacron swabs in the following sequence: outer surface of surgical mask, inner surface of surgical mask, outer surface of cotton mask, and inner surface of cotton mask.
The median viral loads of nasopharyngeal and saliva samples from the 4 participants were 5.66 log copies/mL and 4.00 log copies/mL, respectively. The median viral loads after coughs without a mask, with a surgical mask, and with a cotton mask were 2.56 log copies/mL, 2.42 log copies/mL, and 1.85 log copies/mL, respectively. All swabs from the outer mask surfaces of the masks were positive for SARS–CoV-2, whereas most swabs from the inner mask surfaces were negative (Table).

Objective: To evaluate the effectiveness of surgical and cotton masks in filtering SARS–CoV-2.

Discussion: Neither surgical nor cotton masks effectively filtered SARS–CoV-2 during coughs by infected patients.

Link - https://www.acpjournals.org/doi/10.7326/M20-1342
Archive - https://archive.is/c8I2D


Effects of surgical and FFP2/N95 face masks on cardiopulmonary exercise capacity

Due to the SARS-CoV2 pandemic, medical face masks are widely recommended for a large number of individuals and long durations. The effect of wearing a surgical and a FFP2/N95 face mask on cardiopulmonary exercise capacity has not been systematically reported.

This prospective cross-over study quantitated the effects of wearing no mask (nm), a surgical mask (sm) and a FFP2/N95 mask (ffpm) in 12 healthy males (age 38.1 ± 6.2 years, BMI 24.5 ± 2.0 kg/m2). The 36 tests were performed in randomized order. The cardiopulmonary and metabolic responses were monitored by ergo-spirometry and impedance cardiography. Ten domains of comfort/discomfort of wearing a mask were assessed by questionnaire.

The pulmonary function parameters were significantly lower with mask (forced expiratory volume: 5.6 ± 1.0 vs 5.3 ± 0.8 vs 6.1 ± 1.0 l/s with sm, ffpm and nm, respectively; p = 0.001; peak expiratory flow: 8.7 ± 1.4 vs 7.5 ± 1.1 vs 9.7 ± 1.6 l/s; p < 0.001). The maximum power was 269 ± 45, 263 ± 42 and 277 ± 46 W with sm, ffpm and nm, respectively; p = 0.002; the ventilation was significantly reduced with both face masks (131 ± 28 vs 114 ± 23 vs 99 ± 19 l/m; p < 0.001). Peak blood lactate response was reduced with mask. Cardiac output was similar with and without mask. Participants reported consistent and marked discomfort wearing the masks, especially ffpm.

Ventilation, cardiopulmonary exercise capacity and comfort are reduced by surgical masks and highly impaired by FFP2/N95 face masks in healthy individuals. These data are important for recommendations on wearing face masks at work or during physical exercise.

Link - https://link.springer.com/article/10.1007/s00392-020-01704-y
Archive - https://archive.is/LhG9o


Adverse Effects of Prolonged Mask Use among Healthcare Professionals during COVID-19

Healthcare professionals report side effects of prolonged use of PPE when caring for COVID-19 patients. This study delves into various adverse effects of prolonged mask use and provides recommendations to ease the burden on healthcare professionals.

This is a cross sectional study among healthcare professionals, primarily located in New York City, who worked in the hospital during the COVID-19 pandemic. All respondents completed an anonymous survey consisting of twenty one questions regarding adverse effects of PPE, medical history, and demographics.

A total of 343 healthcare professionals on the COVID-19 front lines participated in this study. The majority were female (n = 315) and 227 were located in New York City. 225 respondents identified as White, 34 as Hispanic, 23 as African American, and 61 as "other" ethnicity. 314 respondents reported adverse effects from prolonged mask use with headaches being the most common complaint (n = 245). Skin breakdown was experienced by 175 respondents, and acne was reported in 182 respondents. Impaired cognition was reported in 81 respondents. Previous history of headaches (n = 98), skin sensitivity (n = 164), and acne (n = 121) were found in some respondents. Some respondents experienced resolved side effects once masks were removed, while others required physical or medical intervention.

Prolonged use of N95 and surgical masks by healthcare professionals during COVID-19 has caused adverse effects such as headaches, rash, acne, skin breakdown, and impaired cognition in the majority of those surveyed. As a second wave of COVID-19 is expected, and in preparation for future pandemics, it is imperative to identify solutions to manage these adverse effects. Frequent breaks, improved hydration and rest, skin care, and potentially newly designed comfortable masks are recommendations for future management of adverse effects related to prolonged mask use.

Link - https://clinmedjournals.org/articles/jide/journal-of-infectious-diseases-and-epidemiology-jide-6-130.php?jid=jide
Archive - https://archive.is/5uEQI


Preliminary report on surgical mask induced deoxygenation during major surgery

This study was undertaken to evaluate whether the surgeons’ oxygen saturation of hemoglobin was affected by the surgical mask or not during major operations.

Repeated measures, longitudinal and prospective observational study was performed on 53 surgeons using a pulse oximeter pre and postoperatively.

Our study revealed a decrease in the oxygen saturation of arterial pulsations (SpO2) and a slight increase in pulse rates compared to preoperative values in all surgeon groups. The decrease was more prominent in the surgeons aged over 35.

Considering our findings, pulse rates of the surgeon's increase and SpO2 decrease after the first hour. This early change in SpO2 may be either due to the facial mask or the operational stress. Since a very small decrease in saturation at this level, reflects a large decrease in PaO2, our findings may have a clinical value for the health workers and the surgeons.

link - https://www.sciencedirect.com/science/article/abs/pii/S1130147308702355 -
archive - https://archive.is/eOjb6


Link broken - https://www.cidrap.umn.edu/news-perspective/2020/04/commentary-masks-all-covid-19-not-


Ryan Christian of TLAV, the man who collected all these papers:
- https://www.thelastamericanvagabond.com -
- https://www.bitchute.com/channel/thelastamericanvagabond/

go to https://hexagod.net/masks_detail_studies.html for links in this document