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Do Masking Policies Work?


One of the more problematic issues around assessing the efficacy of masks is that the PCR diagnostic test is notably unreliable for diagnosis of Covid-19 infection and is not fully FDA licensed to do so.*


Currently the PCR tests have only been granted "emergency use authorization" for Covid-19 and  have NOT been held to rigorous licensing standards for this purpose. 


Thus, using past mask studies prior to Covid-19 on prevention of transmission of flu and other pathogens could provide more reliable insights using time tested FDA approved laboratory analysis and controls. The method of ascertaining infections are noted when possible.



Association between face mask use and risk of SARS-CoV-2 infection: Cross-sectional study

Epidemiology and Infection
November 3, 2023

We examined the association between face masks and risk of infection with SARS-CoV-2 using cross-sectional data from 3,209 participants in a randomized trial exploring the effectiveness of glasses in reducing the risk of SARS-CoV-2 infection. Face mask use was based on participants’ response to the end-of-follow-up survey. We found that the incidence of self-reported COVID-19 was 33% (aRR 1.33; 95% CI 1.03–1.72) higher in those wearing face masks often or sometimes, and 40% (aRR 1.40; 95% CI 1.08–1.82) higher in those wearing face masks almost always or always, compared to participants who reported wearing face masks never or almost never. We believe the observed increase in the incidence of infection associated with wearing a face mask is likely due to unobservable and hence nonadjustable differences between those wearing and not wearing a mask. Observational studies reporting on the relationship between face mask use and risk of respiratory infections should be interpreted cautiously, and more randomized trials are needed.


Physical interventions to interrupt or reduce the spread of respiratory viruses

Cochrane Database Syst Rev.
January 30, 2023

Objectives: To assess the effectiveness of physical interventions to interrupt or reduce the spread of acute respiratory viruses.

Search methods: We searched CENTRAL, PubMed, Embase, CINAHL, and two trials registers in October 2022, with backwards and forwards citation analysis on the new studies.

Selection criteria: We included randomised controlled trials (RCTs) and cluster-RCTs investigating physical interventions (screening at entry ports, isolation, quarantine, physical distancing, personal protection, hand hygiene, face masks, glasses, and gargling) to prevent respiratory virus transmission. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methodological procedures.

Authors' conclusions: The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions. There were additional RCTs during the pandemic related to physical interventions but a relative paucity given the importance of the question of masking and its relative effectiveness and the concomitant measures of mask adherence which would be highly relevant to the measurement of effectiveness, especially in the elderly and in young children. There is uncertainty about the effects of face masks. The low to moderate certainty of evidence means our confidence in the effect estimate is limited, and that the true effect may be different from the observed estimate of the effect. T
he pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection. Hand hygiene is likely to modestly reduce the burden of respiratory illness, and although this effect was also present when ILI and laboratory-confirmed influenza were analysed separately, it was not found to be a significant difference for the latter two outcomes. Harms associated with physical interventions were under-investigated. There is a need for large, well-designed RCTs addressing the effectiveness of many of these interventions in multiple settings and populations, as well as the impact of adherence on effectiveness, especially in those most at risk of ARIs.

CDC Study Finds Majority of Those Infected with COVID-19 ‘Always’ Wore Mask
The CDC as reported by the California Globe
October 13, 2020


The study found 74.2% reported wearing masks “always” while 14.5% wore masks “often,” or 85% almost always wore masks.

It is difficult not to conclude that wearing non-surgical cloth face masks or face coverings does little to prevent contracting the coronavirus.
For each case-patient, two adults with negative SARS-CoV-2 RT-PCR test results were randomly selected as control-participants and matched by age, sex, and study location.


Eight industrial hygienists sent a 27-page letter to the CDC, NIH, and other top US government officials that points out serious flaws in the CDC mask guidance.
January 28, 2022

The key points in their letter


Four key points :

  1. Recommending N-95 type masks is inappropriate for the general population and children

  2. CDC has issued harmful guidance for masking children that contradicts manufacturer’s recommendations, world-wide standard practice and CDC’s own guidance, and without appropriate risk-benefit analysis

  3. The CDC continues to ignore the fact that COVID-19 is primarily spread by aerosols (not droplets) making mask use mostly ineffective

  4. CDC’s position for masks used by the general public lacks proper scientific justification and creates potential harm based on a false sense of security:

We have conducted a peer review of the CDC's “Types of Masks and Respirators” that was updated on January 28, 2022. Our findings have shown that this publication does not meet the scientific integrity that we have come to expect from HHS and all affiliated agencies. Please review the findings in our report. We strongly encourage your team to remove this publication from use and publish an acknowledgement of the concerns. We are willing to discuss our findings further at your request. We appreciate your time and look forward to a response. 

However, I’m pretty sure that there isn’t any scientific integrity left at the CDC and there will be nobody there to answer their complaint.


The CDC is doing enormous damage to science and scientists by allowing politics to dictate public health policy rather than actual science. Increasingly, and for good reason as we have illustrated, the public does not trust the CDC and its science; this must change.


A cluster randomised trial of cloth masks compared with medical masks in healthcare workers.
British Journal of Medicine
April 22, 2015


Objective: The aim of this study was to compare the efficacy of cloth masks to medical masks in hospital healthcare workers (HCWs). The null hypothesis is that there is no difference between medical masks and cloth masks.

Results: The rates of all infection outcomes were highest in the cloth mask arm,  Penetration of cloth masks by particles was almost 97% and medical masks 44%. The rates of chronic respiratory infection, influenza like illness and laboratory-confirmed virus infections were lowest in the medical mask arm, followed by the control arm, and highest in the cloth mask arm.

Conclusions: 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.

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

Center for Disease Control
May 2020

There were 3 influenza pandemics in the 20th century, and there has been 1 so far in the 21st century. Local, national, and international health authorities regularly update their plans for mitigating the next influenza pandemic in light of the latest available evidence on the effectiveness of various control measures in reducing transmission. Here, we review the evidence base on the effectiveness of nonpharmaceutical personal protective measures and environmental hygiene measures in nonhealthcare settings and discuss their potential inclusion in pandemic plans. Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza. We similarly found limited evidence on the effectiveness of improved hygiene and environmental cleaning. We identified several major knowledge gaps requiring further research, most fundamentally an improved characterization of the modes of person-to-person transmission.

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

Canadian Association Medical Journal
May 17, 2016


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. Surrogate exposure studies comparing N95 respirators and surgical masks using manikins or adult volunteers under simulated conditions were summarized separately. Outcomes from clinical studies were laboratory-confirmed respiratory infection, influenza-like illness and workplace absenteeism. Outcomes from surrogate exposure studies were filter penetration, face-seal leakage and total inward leakage.

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 influenza-like illness or  reported workplace absenteeism


In the surrogate exposure studies, N95 respirators were associated with less filter penetration, less face-seal leakage and less total inward leakage under laboratory experimental conditions, compared with surgical masks.

Interpretation: Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.

The lack of clarity has led to conflicting guideline recommendations regarding respiratory protective equipment for the prevention of acute respiratory infections: N95 respirators are recommended in some guidelines but not others. Since the outbreak of severe acute respiratory syndrome (SARS 2016), there has been a heightened level of controversy within Canada in determining the optimal ways to protect health care workers from respiratory pathogens.


Conflicting recommendations from federal and provincial health authorities lead to confusion among heath care workers, which can result in lack of adherence to basic infection control principles and practices.

We performed a systematic review to assess and synthesize the available body of literature regarding N95 respirators versus surgical masks for the protection of health care workers against acute respiratory infections in a health care setting.

Face masks to prevent transmission of influenza virus: a systematic review

Cambridge University Press:

January 22,  2010

On 18 August 2009 we searched the following databases for articles published in English from January 1960 to August 2009: PubMed (1960–2009), Science Citation Index (Web of Science) (1970–2009), and the Cochrane Library (1988–2009). We searched for articles using the following search strategy:

Our review highlights the limited evidence base supporting the efficacy or effectiveness of face masks to reduce influenza virus transmission. An important concern when determining which public health interventions could be useful in mitigating local influenza virus epidemics, and which infection control procedures are necessary to prevent nosocomial transmission, is the mode of influenza virus transmission between people and in the environment. Physical barriers would be most effective in limiting short-distance transmission by direct or indirect contact and large droplet spread, while more comprehensive precautions would be required to prevent infection at longer distances via airborne spread of small (nuclei) droplet particles 


In healthcare settings, stringent precautions are recommended to protect against pathogens that are transmitted by the airborne route, including the use of N95-type respirators (which require fit testing), other personal protective equipment including gowns, gloves, head covers and face shields, and isolation of patients in negative-pressure rooms There remains considerable controversy over the relative importance of the alternative modes of transmission for influenza virus. In a recent review, Brankston and colleagues concluded that natural influenza transmission in human beings occurs generally over short distance rather than over long distance. Based on the same evidence, Tellier had earlier concluded that aerosol transmission occurs at appreciable rates, and cited further evidence in an updated review. Weber & Stilianakis found that contact, large droplet and small droplet (aerosol) transmission are all potentially important modes of transmission for influenza virus.

If airborne transmission were important, it would be less likely that surgical masks will lead to reductions in infectiousness or protection against infection, if worn by ill or uninfected people, respectively. The primary argument against airborne transmission is as much one of absence of evidence as evidence of absence. While there are documented examples of long-distance airborne transmission of other pathogens including varicella zoster virus and Mycobacterium tuberculosis, the literature contain few compelling examples of airborne transmission of influenza virus and several reports of scenarios where airborne transmission did not occur. 


In future similar studies it would be important to consider the potential for leakage around the sides of the mask in addition to direct penetration of infectious viral particles through the mask, if the results are to have practical implications for reduction of transmission in community and other settings. Further studies are needed to investigate how mask and respirator performance varies with temperature and humidity, or under working conditions when moisture in exhaled breath or sweat may build up in face masks and hinder filtration or fit.


One concern over the use of face masks or respirators in healthcare settings is the potential for negative psychosocial impacts on patients and children in particular, especially in regions outside Asia where masks are not routinely worn.


Long-term use of N95-type respirators is likely to lead to physical discomfort, and has been associated with headaches

Pandemic guidance provided by the World Health Organization for community settings advises that masks may be worn although effectiveness is uncertain particularly in open spaces.  Other health agencies, such as the US Centers for Disease Control and Prevention, are not recommending masks in the community setting, with the exception of high-risk individuals who care for the sick or spend time in large crowds in areas affected by the pandemic. .


Wearing masks incorrectly may increase the risk of transmission.  Further studies of face mask use are now underway, including some with prospective designs that follow cohorts of initially uninfected people. These studies will be particularly important in addressing compliance to and effectiveness associated with sustained use of face masks beyond the acute scenarios of existing studies [1416]. While fewer resources are required to conduct studies with outcomes based on self-reported signs and symptoms of acute respiratory infection, future studies could include acute and convalescent serology or repeated collection of clinical specimens to provide results specific to influenza virus infection.

In conclusion there remains a substantial gap in the scientific literature on the effectiveness of face masks to reduce transmission of influenza virus infection. While there is some experimental evidence that masks should be able to reduce infectiousness under controlled conditions, there is less evidence on whether this translates to effectiveness in natural settings. There is little evidence to support the effectiveness of face masks to reduce the risk of infection. Current research has several limitations including underpowered samples, limited generalizability, narrow intervention targeting and inconsistent testing protocols, different laboratory methods, and case definitions. Further in-vivo studies of face masks in infectious individuals are warranted to determine the proportion of exhaled virus that is trapped by the mask.

* Excellent video on how the PCR test works, or doesn't, when used as a diagnostic tool.









        More resources

The Foegen Effect: Why Face Masks Increase the Death Rate of COVID-19

Feb 18, 2022

This study, based on the U.S. state of Kansas: case mortality was significantly lower in counties without mandatory masks. Mandatory masking increased case mortality there by 85%. Even after factoring in the reduced number of cases due to masks, the numbers still remain 52% higher.

Disposable surgical face masks for preventing surgical wound infection in clean surgery (Review)
Cochrane Review
Main results We included three trials, involving a total of 2106 participants. There was no statistically significant difference in infection rates between the masked and unmasked group in any of the trials. We identified no new trials for this latest update.

Naked Surgeons? The Debate About What to Wear in the Operating Room

Clinical Infectious Disease
There is no evidence regarding SSI risk related to operating room attire except for sterile gowns and the use of gloves. Naked surgeons shed fewer bacteria into the operating room environment than ones wearing scrub suits.


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

 American Journal of Infection Control

N95-masked health-care workers (HCW) were significantly more likely to experience headaches. Face mask use in HCW was not demonstrated to provide benefit in terms of cold symptoms or getting colds.


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

Influenza and Other Respiratory Viruses

There were 17 eligible studies. … None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.


Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis  
J. Clinical Infectious Diseases
Self-reported assessment of clinical outcomes was prone to bias. Evidence of a protective effect of masks or respirators against verified respiratory infection (VRI) was not statistically significant.


N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial 

Among 2862 randomized participants, 2371 completed the study and accounted for 5180 HCW-seasons. … Among outpatient health care personnel, N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza.


Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis

J Evid Based Med.

A total of six RCTs involving 9,171 participants were included. There were no statistically significant differences in preventing laboratory-confirmed influenza, laboratory-confirmed respiratory viral infections, laboratory-confirmed respiratory infection, and influenza-like illness using N95 respirators and surgical masks. Meta-analysis indicated a protective effect of N95 respirators against laboratory-confirmed bacterial colonization (RR = 0.58, 95% CI 0.43-0.78). The use of N95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza.

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