October 4, 2022
Dear Friends and Family,
The subject of masks is undoubtedly the most talked about mitigation topic throughout the pandemic. Even today there are questions and doubts as to their effectiveness. This is undoubtedly the result of very inconsistent information occurring early in the pandemic which continued through the duration.
The attached PDF has a plethora of opinions. The text contains the excerpts from those authors I consider most qualified to present an opinion.
My takeaways are as follows.
Happy Learning,
Harley
Dear Friends and Family,
The subject of masks is undoubtedly the most talked about mitigation topic throughout the pandemic. Even today there are questions and doubts as to their effectiveness. This is undoubtedly the result of very inconsistent information occurring early in the pandemic which continued through the duration.
The attached PDF has a plethora of opinions. The text contains the excerpts from those authors I consider most qualified to present an opinion.
My takeaways are as follows.
- Masks do provide some benefit assuming they are properly fitted and are clean. The N95 masks provide more protection than surgical masks and surgical masks provide more protection than single layer masks. The amount of protection from each is not definitively quantified for Covid. There is no evidence that any U.S. Public Health agency conducted a clinical trial to determine the efficacy of the various masks for Covid.
- Masks do a better job of protecting others from you if you are infected, than protecting you from other infected persons.
- Approximately 24% of all transmission are from asymptomatic people, so masking an entire population does reduce transmission to some degree.
Happy Learning,
Harley
COVID PANDEMIC CRITIQUE – SEGMENT 8
CONTROLLING THE SPREAD: MASKS -- EXCERPTS
THE SCIENCE AT THE START OF THE PANDEMIC: The CDC guidelines made no mention of masks preventing the wearer from infection. Americans have common sense, and the CDC recommendations on masks did not pass the commonsense test. I believed from the beginning that masks could partially prevent the wearer from transmitting and receiving the virus. How effective were they at doing both? Simple tests could be done to determine this. For weeks in the White House Task Force meetings, we’d discussed the need to get these inexpensive tests perform to ensure that we were distributing effective protection. We needed to know how well cloth masks worked – at least in the laboratory. It would have taken a matter of mere hours to get such tests done and analyzed.
As coronavirus response coordinator, I wasn’t empowered to execute or fund such tests. Worse, I couldn’t direct anyone else to get it done by private laboratories. I asked the CDC, the NIH, ASPR, and the FDA to move on testing the efficacy of various cloth, surgical, and N95 masks so the American people would have the clear, definitive information they needed to inform their actions. Unfortunately, territorial stickiness again gummed up the works. The CDC was the logical choice for carrying out such tests, but the agency seemed paralyzed on this point. Why it didn’t devise and then execute tests on masks remained a constant frustration, and a mystery to me. I prodded and prodded, but never received a satisfactory answer. As for the NIH, ASPR, and the FDA, they didn’t believe that pursuing this kind of testing was part of their job. So, definitive tests on masks didn’t get done by the federal agencies. Instead, university labs, private-sector labs, and even CNN had the tests performed – but these weren’t systematic enough for the CDC or the task force to make data-driven recommendations. Without a definitive statement one way or the other about the effectiveness of masks as two-way protectors, the public became confused, frustrated, and ultimately, angry and distrustful.
Two important pieces of science came in during the first week of November that substantiated the plan we had developed. The first was a Japanese study showing that masks did provide bidirectional protection, protecting both the wearer and those around them. This contradicted what had been the CDC’s official position since April of only protecting others, not the wearer. The second was an article published in the International Journal of Infectious Diseases, titled “Asymptomatic SARS Coronavirus 2 infection: Invisible Yet Invincible.” The October 2020 Japanese article did what we had been asking for since March. They studied the effectiveness of various kinds of masks and published the results, finding cloth masks 20 – 40% effective and N95 masks 80-90 % protective for the infected wearer. The percentage increases to 50% and 99% in preventing escape of viral particles from the infected wearer. On May 13, 2021, the CDC director announced that the fully vaccinated no longer needed to wear masks, she characterized this as the moment “we all longed for.”
Source: Silent Invasion by Dr. Deborah Birx (2022).
THE SCIENCE SPRING-SUMMER OF 2020. What was scientifically known then?
Beyond those summaries of research in respiratory viruses, a large amount of empirical evidence accumulated from all over the world about masks for COVID-19. That evidence – based in real-life experience—was clear and consistent. Mask usage failed to stop or prevent surges in cases in dozens of cities, states, and countries.
Source: A Plague Upon Our House by Scott W. Atlas MD (2021)
The prevailing word at the beginning of the pandemic was that unless you were sick, you didn’t need to wear a face mask. Americans were explicitly told NOT to wear masks initially by not only U.S. infectious disease experts but also the World Health Organization (WHO). By early April, many public health experts reached a consensus encouraging the public to wear a face mask to lower infection rates, even if some only offered a 15% reduction – the country was desperate. The U.S. CDC recommended voluntary wearing of public face masks April 2020; the WHO waited until June 5 before offering such recommendations.
By mid-August, The Wall Street Journal reported the existence of “growing evidence that facial coverings help prevent transmission – even if an infected wearer is in close contact with others.” It cited recent studies, including one in Physics of Fluids, which showed that “Well-fitted homemade masks with multiple layers of quilting fabric, and off-the-shelf cone style masks, proved to be the most effective in reducing droplet dispersal. These masks were able to curtail the speed and range of the respiratory jets significantly, albeit with some leakage through the mask material and from small gaps along the edges. A study out of Singapore published in September 2020 showed multilayer cotton and surgical masks significantly reduced the number of particles expelled, with a reduction of 86.4% and 99.9% respectively. However, the study revealed that some mask alternatives, such as single-layer coverings offered little protection against infection, similar to prior studies on SARS.
To further add to the conversation, Joe Biden recommended that the federal government – as distinguished from state and local governments – mandate generalized public mask wearing at all times. Yet even as the scientific evidence continued to grow showing that masks represented a viable way of reducing transmission because of the high proportion of asymptomatic and pre-symptomatic transmission, there was a lack of evidence of the magnitude of such effects, especially at a population level.
Source: Panic Attack by Nicole Saphier, MD (2021).
In the absence of good information, bad information was able to guide the debate. Perhaps nowhere did this play out with more conflict and misfortune than in the debate over masks. There was a long-standing ambivalence at the CDC toward the use of masks. One White House task force member told me that the CDC raised concerns that masks would end up encouraging consumers who wore them to touch their face more, and in turn make them most likely to spread infection through fomites. The concerns were based in part on the CDC’s flawed premise that more of the early transmission was being driven by droplets and contaminated surfaces rather than aerosolization. Masks had never been viewed as a standard part of the response to a pandemic. In fact, the much-discussed pandemic plan that the Obama administration had provided to the incoming Trump team didn’t take up the issue of widespread masking as a potential approach to containing a pandemic, or even mention masks a single time.
Wearing a mask was in many respects an act of civic virtue, a way to protect your friends and neighbors if you were one of those individuals who was unknowingly infected and at risk of becoming a super-spreader. Many cloth masks weren’t intended to protect you from getting infected, although a high-quality cloth mask would provide a person with some protection. To secure more robust protection, a person would need a higher quality N95 mask. The idea of cloth masks, simply put, was to protect others from you, not you from others, a distinction I made often. But the whole premise of mask wearing quickly became a faux protest, an expression of disdain that some people felt for government directives that brought us shutdowns, closed schools, and other restrictions.
Source: Uncontrolled Spread by Scott Gottlieb, MD (2021)
THE SCIENCE PER DR. FAUCI and DR. REDFIELD: Dr. Fauci appeared on 60 Minutes in March 2020, and very clearly voiced his opinion on masking: “There’s no reason to be walking around with masks.” He went further, specifically describing how scientifically ineffective and even potentially harmful masks could be: “When you’re in the middle of an outbreak, wearing a mask might make people feel a little bit better and it might even block a droplet, but it’s not providing the perfect protection that people think that it is. And, often, there are unintended consequences – people fiddling with the mask, and they keep touching their face.” Yet, Fauci joined with the CDC in recommending universal cloth masking less than a month after publicly stating they wouldn’t work. When questioned about this in June 2020, his defense amounted to admitting to misleading the public about mask efficacy in order to protect supplies for health care workers.
Notably, Fauci gave a specific explanation of the inherent flaws of masks purchased by the general public: that the virus is too small and passes right through the material. On March 31, just a few days before the CDC’s new recommendation for universal masking, he received an email from Andrea Lerner, another employee at NIAID and the National Institutes of Health. Lerner confirmed what the entire scientific community already knew; that there was no evidence that masking reduced transmission of influenza-like illnesses.
Source: Unmasked by Ian Miller (2022)
CONTROLLING THE SPREAD: MASKS -- EXCERPTS
THE SCIENCE AT THE START OF THE PANDEMIC: The CDC guidelines made no mention of masks preventing the wearer from infection. Americans have common sense, and the CDC recommendations on masks did not pass the commonsense test. I believed from the beginning that masks could partially prevent the wearer from transmitting and receiving the virus. How effective were they at doing both? Simple tests could be done to determine this. For weeks in the White House Task Force meetings, we’d discussed the need to get these inexpensive tests perform to ensure that we were distributing effective protection. We needed to know how well cloth masks worked – at least in the laboratory. It would have taken a matter of mere hours to get such tests done and analyzed.
As coronavirus response coordinator, I wasn’t empowered to execute or fund such tests. Worse, I couldn’t direct anyone else to get it done by private laboratories. I asked the CDC, the NIH, ASPR, and the FDA to move on testing the efficacy of various cloth, surgical, and N95 masks so the American people would have the clear, definitive information they needed to inform their actions. Unfortunately, territorial stickiness again gummed up the works. The CDC was the logical choice for carrying out such tests, but the agency seemed paralyzed on this point. Why it didn’t devise and then execute tests on masks remained a constant frustration, and a mystery to me. I prodded and prodded, but never received a satisfactory answer. As for the NIH, ASPR, and the FDA, they didn’t believe that pursuing this kind of testing was part of their job. So, definitive tests on masks didn’t get done by the federal agencies. Instead, university labs, private-sector labs, and even CNN had the tests performed – but these weren’t systematic enough for the CDC or the task force to make data-driven recommendations. Without a definitive statement one way or the other about the effectiveness of masks as two-way protectors, the public became confused, frustrated, and ultimately, angry and distrustful.
Two important pieces of science came in during the first week of November that substantiated the plan we had developed. The first was a Japanese study showing that masks did provide bidirectional protection, protecting both the wearer and those around them. This contradicted what had been the CDC’s official position since April of only protecting others, not the wearer. The second was an article published in the International Journal of Infectious Diseases, titled “Asymptomatic SARS Coronavirus 2 infection: Invisible Yet Invincible.” The October 2020 Japanese article did what we had been asking for since March. They studied the effectiveness of various kinds of masks and published the results, finding cloth masks 20 – 40% effective and N95 masks 80-90 % protective for the infected wearer. The percentage increases to 50% and 99% in preventing escape of viral particles from the infected wearer. On May 13, 2021, the CDC director announced that the fully vaccinated no longer needed to wear masks, she characterized this as the moment “we all longed for.”
Source: Silent Invasion by Dr. Deborah Birx (2022).
THE SCIENCE SPRING-SUMMER OF 2020. What was scientifically known then?
- In April 2020, New England Journal of Medicine: “We know that wearing a mask outside health care facilities offers little, if any, protection from infection …. In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic.”
- The CDC in May 2020 published a thorough review of influenza pandemics and concluded “we did not find evidence that surgical-type face masks are effective in reducing transmission, either when worn by infected persons (source control) or by persons in the general community to reduce their susceptibility.”
- In WHO’s June 2020 “Advice on the Use of Masks in the Context of COVID-19,” they summarized by stating, “At present, there is no direct evidence on the effectiveness of universal masking of healthy people in the community to prevent infection with respiratory viruses, including COVID—19” and “there are potential benefits and harms to consider” in December 2020, as well.
- On July 23, 2020, Tom Jefferson and Carl Heneghan of University of Oxford’s Center for Evidence-Based Medicine reviewed the scientific literature and wrote, “It would appear that despite two decades of pandemic preparedness, there is considerable uncertainty as to the value of wearing masks.”
- In November 2020, after its original submission and difficult-to-justify rejection by several journals, Annal of Internal Medicine finally published Denmark’s “randomized, controlled” Danmask-19 study. That seminal study – of the highest scientific quality in clinical trial research – evaluated masks in more than 6,000 adult participants. That study showed there was no statistically significant difference between those who wore masks and those who did not when it came to being infected by the SAR2 coronavirus
Beyond those summaries of research in respiratory viruses, a large amount of empirical evidence accumulated from all over the world about masks for COVID-19. That evidence – based in real-life experience—was clear and consistent. Mask usage failed to stop or prevent surges in cases in dozens of cities, states, and countries.
- In the U.S., 38 states had mandates for masks since the summer of 2020, and most of the others had mask mandates in their major cities. Data from Gallup, YouGov, the Covid-19 Consortium, the CDC, and elsewhere showed that approximately 80% or more of Americans had been wearing masks since the late summer of 2020, equal to or surpassing most Western European nations and approaching the levels in Asia. There was no evidence that masks stopped surges in cases.
- Outside the US, countries far and wide had long implemented mask mandates, and they too were wearing them. Yet cases surged through those mandates. It certainly was not hard to find examples from spring-summer-fall of 2020 – Austria, Belgium, France, Germany, Israel, Italy, Japan, Portugal, Spain, and the UK, just for a start. In South Korea, when a full 99% of people were wearing masks for months, cases exploded through their police-enforced mask mandates.
Source: A Plague Upon Our House by Scott W. Atlas MD (2021)
The prevailing word at the beginning of the pandemic was that unless you were sick, you didn’t need to wear a face mask. Americans were explicitly told NOT to wear masks initially by not only U.S. infectious disease experts but also the World Health Organization (WHO). By early April, many public health experts reached a consensus encouraging the public to wear a face mask to lower infection rates, even if some only offered a 15% reduction – the country was desperate. The U.S. CDC recommended voluntary wearing of public face masks April 2020; the WHO waited until June 5 before offering such recommendations.
By mid-August, The Wall Street Journal reported the existence of “growing evidence that facial coverings help prevent transmission – even if an infected wearer is in close contact with others.” It cited recent studies, including one in Physics of Fluids, which showed that “Well-fitted homemade masks with multiple layers of quilting fabric, and off-the-shelf cone style masks, proved to be the most effective in reducing droplet dispersal. These masks were able to curtail the speed and range of the respiratory jets significantly, albeit with some leakage through the mask material and from small gaps along the edges. A study out of Singapore published in September 2020 showed multilayer cotton and surgical masks significantly reduced the number of particles expelled, with a reduction of 86.4% and 99.9% respectively. However, the study revealed that some mask alternatives, such as single-layer coverings offered little protection against infection, similar to prior studies on SARS.
To further add to the conversation, Joe Biden recommended that the federal government – as distinguished from state and local governments – mandate generalized public mask wearing at all times. Yet even as the scientific evidence continued to grow showing that masks represented a viable way of reducing transmission because of the high proportion of asymptomatic and pre-symptomatic transmission, there was a lack of evidence of the magnitude of such effects, especially at a population level.
Source: Panic Attack by Nicole Saphier, MD (2021).
In the absence of good information, bad information was able to guide the debate. Perhaps nowhere did this play out with more conflict and misfortune than in the debate over masks. There was a long-standing ambivalence at the CDC toward the use of masks. One White House task force member told me that the CDC raised concerns that masks would end up encouraging consumers who wore them to touch their face more, and in turn make them most likely to spread infection through fomites. The concerns were based in part on the CDC’s flawed premise that more of the early transmission was being driven by droplets and contaminated surfaces rather than aerosolization. Masks had never been viewed as a standard part of the response to a pandemic. In fact, the much-discussed pandemic plan that the Obama administration had provided to the incoming Trump team didn’t take up the issue of widespread masking as a potential approach to containing a pandemic, or even mention masks a single time.
Wearing a mask was in many respects an act of civic virtue, a way to protect your friends and neighbors if you were one of those individuals who was unknowingly infected and at risk of becoming a super-spreader. Many cloth masks weren’t intended to protect you from getting infected, although a high-quality cloth mask would provide a person with some protection. To secure more robust protection, a person would need a higher quality N95 mask. The idea of cloth masks, simply put, was to protect others from you, not you from others, a distinction I made often. But the whole premise of mask wearing quickly became a faux protest, an expression of disdain that some people felt for government directives that brought us shutdowns, closed schools, and other restrictions.
Source: Uncontrolled Spread by Scott Gottlieb, MD (2021)
THE SCIENCE PER DR. FAUCI and DR. REDFIELD: Dr. Fauci appeared on 60 Minutes in March 2020, and very clearly voiced his opinion on masking: “There’s no reason to be walking around with masks.” He went further, specifically describing how scientifically ineffective and even potentially harmful masks could be: “When you’re in the middle of an outbreak, wearing a mask might make people feel a little bit better and it might even block a droplet, but it’s not providing the perfect protection that people think that it is. And, often, there are unintended consequences – people fiddling with the mask, and they keep touching their face.” Yet, Fauci joined with the CDC in recommending universal cloth masking less than a month after publicly stating they wouldn’t work. When questioned about this in June 2020, his defense amounted to admitting to misleading the public about mask efficacy in order to protect supplies for health care workers.
Notably, Fauci gave a specific explanation of the inherent flaws of masks purchased by the general public: that the virus is too small and passes right through the material. On March 31, just a few days before the CDC’s new recommendation for universal masking, he received an email from Andrea Lerner, another employee at NIAID and the National Institutes of Health. Lerner confirmed what the entire scientific community already knew; that there was no evidence that masking reduced transmission of influenza-like illnesses.
Source: Unmasked by Ian Miller (2022)
I am going to comment as the CDC director that face masks, these face masks, are the most important public health tool we have. And I will continue to appeal to all Americans, all individuals in our country, to embrace these face coverings. I might even go so far as to say that this face mask is more guaranteed to protect me against Covid than when I take the Covid vaccine.
Source: Faucian Bargain by Steve Deace & Todd Erzen (2021).
MEDICAL JOURNAL – JAMA: Community mask wearing substantially reduces transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2 ways. First, masks prevent infected persons from exposing others to SARS-CoV-2 by blocking exhalation of virus-containing droplets into the air (termed source control). This aspect of mask wearing is especially important because it is estimated that at least 50% or more of transmission are from persons who never develop symptoms or those who are in the pre-symptomatic phase of COVID-19 illness. In recent laboratory experiments, multilayer cloth masks were more effective than single-layer masks, blocking as much as 50% to 70% of exhaled small droplets and particles. Second, masks protect uninfected wearers. However, the observed effectiveness of cloth masks to protect the wearer is lower than their effectiveness for source control, and the filtration capacity of cloth masks can be highly dependent on design, fit, and materials used. Standards for cloth masks are needed to help consumers select marketed products.
Source: Effectiveness of Mask Wearing to Control Community Spead of SARS-CoV-2 Jama Insights by John T Brooks, MD and Jay C. Butler, MD (February 10, 2021).
LARGE SCALE STUDY BY STANFORD MEDICINE: A large, randomized trial led by researchers at Stanford Medicine and Yale University has found that with a surgical face mask over the mouth and nose is an effective way to reduce the occurrence of COVID-19 in community settings. The researcher enrolled nearly 350,000 people from 600 villages in rural Bangladesh. Those living in villages randomly assigned to a series of interventions promoting the use of surgical masks were less likely than those living in control villages to develop COVID-19, which is caused by infection with the SARS-CoV-2 virus, during the eight-week study period.
There were significantly fewer COVID-19 cases in villages with surgical masks compared with the control villages. This aligns with lab tests showing that surgical masks have better filtration than cloth masks. However, cloth masks did reduce the overall likelihood of experiencing symptoms of respiratory illness during the study period. The interventions were rolled out in waves from mid-November to early January. About 7.6% of people in the intervention villages reported COVID-19 symptoms compared with about 8.6% of those in the control villages during the eight-week period – a statistically significant difference that indicates a roughly 12% reduction in the risk of experiencing respiratory symptoms. As a group, those ages 50 to 60 were 23% less likely to develop COVID-19 if they wore a surgical mask; those over 60 were 35% less likely if they did.
Our study provides strong evidence that mask wearing can interrupt the transmission of SARS-CoV-2. It also suggests that filtration efficiency is important. This includes the fit of the mask as well as the materials from which it is made. A cloth mask is certainly better than nothing. But now might be a good time to consider upgrading to a surgical mask.
Source: Surgical Masks Reduce COVID-19 Spread, large-scale study shows Stanford Medicine New Center by Krista Conger (September 1, 2021).
FEBRUARY 11, 2022, CDC GUIDANCE REPORT: The real-world effectiveness of face coverings to prevent acquisition of SARS-CoV-2 infection has not been widely studied. What is added by this report? Consistent use of a face mask or respirator in indoor settings was associated with lower odds of a positive SARS-CoV-2 test result. What are the implications for public health practice? In addition to being up to date with recommended COVID-19 vaccinations, consistently wearing a comfortable well-fitting face mask or respirator in indoor public setting protects against acquisition of SARS-CoV-2 infection; a respirator offers the best protection. The California Study: A test-negative design case-control study enrolled randomly selected California residents who had received a test result for SARS-CoV-2 during February 18 – December 1, 2021. Face mask or respirator use was assessed among 652 case-participants (residents who had received positive rest result for SARS-CoV-2) and 1,176 matched control-participants (residents who had received negative test results for SARS-CoV-2) who self-reported being in indoor public setting during the 2 weeks preceding testing and who reported no known contact with anyone with confirmed or suspected SARS-CoV-2 infection during this time. Results: Wearing an N95/KN95 respirator or wearing a surgical mask was associated with lower adjusted odds of a positive test result compared with not wearing a mask. Wearing a cloth mask was associated with lower adjusted odds of a positive test compared with never wearing a face covering but was not statistically significant. Findings: This highlights the importance of improving access to high-quality masks to ensure access is not a barrier to use. Using a respirator offers the highest level of protection from acquisition of SARS-CoV-2 infection, although it is most important to wear a well-fitting mask or respirator that is comfortable and can be used consistently.
CURRENT CDC GUIDANCE – August 11, 2022 – CDC Streamlines COVID-19 guidance to help the public better protect themselves and understand the risk.
In support of this update CDC is:
Note: The above is just an excerpt from the press release but it captures the essence of the guidance. Interestingly all of the guidance relative to masks is to prevent those who are symptomatic from spreading the virus to others. It makes no mention of wearing masks for protection of getting Covid from others.
ASYMPTOMATIC STUDIES: The Lancet Regional Health – Europe reported that asymptomatic index cases (AIC) played on important role in the transmission and spread of SARS-CoV-2 infections. Thirteen studies agree that AIC transmit SARS-COV2 to contacts, although to a somewhat lesser extent than symptomatic cases (SIC).
Source: The Lancet Regional Health – Europe “Do asymptomatic carriers of SARS-CoV-2 transmit the virus? By Claude P. Muller (March 20, 2021)
Objective: To assess the proportion of SARS-CoV-2 transmissions in the community that likely occur from persons without symptoms.
Result: The baseline assumptions for the model were that peak infectiousness occurred at the median of symptom onset and that 30% of individuals with infection never develop symptoms and are 75% as infectious as those who do develop symptoms. Combined, these baseline assumptions imply that persons with infection who never developed symptoms may account for approximately 24% of all transmission.
Source: JAMA Network “SARS-CoV-2 Transmission from People without COVID-19 Symptoms” by Michael A Johansson PhD et al. (January 7, 2021).
The unabbreviated version of the above can be found in the pdf document below.
MEDICAL JOURNAL – JAMA: Community mask wearing substantially reduces transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2 ways. First, masks prevent infected persons from exposing others to SARS-CoV-2 by blocking exhalation of virus-containing droplets into the air (termed source control). This aspect of mask wearing is especially important because it is estimated that at least 50% or more of transmission are from persons who never develop symptoms or those who are in the pre-symptomatic phase of COVID-19 illness. In recent laboratory experiments, multilayer cloth masks were more effective than single-layer masks, blocking as much as 50% to 70% of exhaled small droplets and particles. Second, masks protect uninfected wearers. However, the observed effectiveness of cloth masks to protect the wearer is lower than their effectiveness for source control, and the filtration capacity of cloth masks can be highly dependent on design, fit, and materials used. Standards for cloth masks are needed to help consumers select marketed products.
Source: Effectiveness of Mask Wearing to Control Community Spead of SARS-CoV-2 Jama Insights by John T Brooks, MD and Jay C. Butler, MD (February 10, 2021).
LARGE SCALE STUDY BY STANFORD MEDICINE: A large, randomized trial led by researchers at Stanford Medicine and Yale University has found that with a surgical face mask over the mouth and nose is an effective way to reduce the occurrence of COVID-19 in community settings. The researcher enrolled nearly 350,000 people from 600 villages in rural Bangladesh. Those living in villages randomly assigned to a series of interventions promoting the use of surgical masks were less likely than those living in control villages to develop COVID-19, which is caused by infection with the SARS-CoV-2 virus, during the eight-week study period.
There were significantly fewer COVID-19 cases in villages with surgical masks compared with the control villages. This aligns with lab tests showing that surgical masks have better filtration than cloth masks. However, cloth masks did reduce the overall likelihood of experiencing symptoms of respiratory illness during the study period. The interventions were rolled out in waves from mid-November to early January. About 7.6% of people in the intervention villages reported COVID-19 symptoms compared with about 8.6% of those in the control villages during the eight-week period – a statistically significant difference that indicates a roughly 12% reduction in the risk of experiencing respiratory symptoms. As a group, those ages 50 to 60 were 23% less likely to develop COVID-19 if they wore a surgical mask; those over 60 were 35% less likely if they did.
Our study provides strong evidence that mask wearing can interrupt the transmission of SARS-CoV-2. It also suggests that filtration efficiency is important. This includes the fit of the mask as well as the materials from which it is made. A cloth mask is certainly better than nothing. But now might be a good time to consider upgrading to a surgical mask.
Source: Surgical Masks Reduce COVID-19 Spread, large-scale study shows Stanford Medicine New Center by Krista Conger (September 1, 2021).
FEBRUARY 11, 2022, CDC GUIDANCE REPORT: The real-world effectiveness of face coverings to prevent acquisition of SARS-CoV-2 infection has not been widely studied. What is added by this report? Consistent use of a face mask or respirator in indoor settings was associated with lower odds of a positive SARS-CoV-2 test result. What are the implications for public health practice? In addition to being up to date with recommended COVID-19 vaccinations, consistently wearing a comfortable well-fitting face mask or respirator in indoor public setting protects against acquisition of SARS-CoV-2 infection; a respirator offers the best protection. The California Study: A test-negative design case-control study enrolled randomly selected California residents who had received a test result for SARS-CoV-2 during February 18 – December 1, 2021. Face mask or respirator use was assessed among 652 case-participants (residents who had received positive rest result for SARS-CoV-2) and 1,176 matched control-participants (residents who had received negative test results for SARS-CoV-2) who self-reported being in indoor public setting during the 2 weeks preceding testing and who reported no known contact with anyone with confirmed or suspected SARS-CoV-2 infection during this time. Results: Wearing an N95/KN95 respirator or wearing a surgical mask was associated with lower adjusted odds of a positive test result compared with not wearing a mask. Wearing a cloth mask was associated with lower adjusted odds of a positive test compared with never wearing a face covering but was not statistically significant. Findings: This highlights the importance of improving access to high-quality masks to ensure access is not a barrier to use. Using a respirator offers the highest level of protection from acquisition of SARS-CoV-2 infection, although it is most important to wear a well-fitting mask or respirator that is comfortable and can be used consistently.
CURRENT CDC GUIDANCE – August 11, 2022 – CDC Streamlines COVID-19 guidance to help the public better protect themselves and understand the risk.
In support of this update CDC is:
- Continuing to promote the importance of being up to date with vaccinations.
- Updating its guidance for people who are not up to date on COVID-19 vaccines on what to do if exposed to someone with COVID-19
- Recommending that instead of quarantining if you were exposed to COVID-19, you wear a high-quality mask for 10 days and get tested on day 5.
- Recommending that if you test positive for COVID-19, you stay home for at least 5 days and isolate from others in your home. You are likely most infectious during these first 5 days. Wear a high-quality mask when you must be around others at home and in public.
Note: The above is just an excerpt from the press release but it captures the essence of the guidance. Interestingly all of the guidance relative to masks is to prevent those who are symptomatic from spreading the virus to others. It makes no mention of wearing masks for protection of getting Covid from others.
ASYMPTOMATIC STUDIES: The Lancet Regional Health – Europe reported that asymptomatic index cases (AIC) played on important role in the transmission and spread of SARS-CoV-2 infections. Thirteen studies agree that AIC transmit SARS-COV2 to contacts, although to a somewhat lesser extent than symptomatic cases (SIC).
Source: The Lancet Regional Health – Europe “Do asymptomatic carriers of SARS-CoV-2 transmit the virus? By Claude P. Muller (March 20, 2021)
Objective: To assess the proportion of SARS-CoV-2 transmissions in the community that likely occur from persons without symptoms.
Result: The baseline assumptions for the model were that peak infectiousness occurred at the median of symptom onset and that 30% of individuals with infection never develop symptoms and are 75% as infectious as those who do develop symptoms. Combined, these baseline assumptions imply that persons with infection who never developed symptoms may account for approximately 24% of all transmission.
Source: JAMA Network “SARS-CoV-2 Transmission from People without COVID-19 Symptoms” by Michael A Johansson PhD et al. (January 7, 2021).
The unabbreviated version of the above can be found in the pdf document below.
| covid_8l_masks_--_segment_8.pdf |