Face masks don't work. OK, here's a clarification: 

Based on the data from randomized controlled trials (RCTs), there is no clear scientific confirmation that face masks work in preventing the transmission of influenza in home or community settings.

Before we go on, nothing in here is to say you shouldn't wear a mask. Feel free. Just don't force me to wear one.

But if we're going to follow the "science," you should know that there is little evidence to support the efficacy of wearing face masks in preventing the spread of influenza in the home or community.

Of course, it is possible that SARS-Cov-2 and COVID-19 are so fundamentally different from every prior pandemic-causing respiratory virus encountered by modern science that all the testing listed below is irrelevant. Not likely, but possible. 

If you take the position that COVID-19 is different, then no need to read any further. But please also admit that there are still no "science" supporting the notion that masks help stop the spread of COVID-19 -- especially masks for asymptomatic people wearing masks, and double especially those cloth masks.

It's propaganda. Vitue signaling. A "best guess" protection perhaps. It might even seem to make logical sense, but there is no clear scientific evidence that masks stop virus spread.

What does the scientific evidence say?

1. WHO -- NO EVIDENCE MASKS ARE EFFECTIVE, BUT DO IT!

Based on "moderate" quality of evidence, in September 2019 the WHO found that "Ten RCTs (random controlled tests) were included in the meta-analysis, and there was no evidence that face masks are effective in reducing transmission of laboratory-confirmed influenza." Despite the lack of evidence, the WHO recommended:

--Asymptomatic: conditionally recommended
--Symptomatic: always recommended

With this disclaimer:  "Although there is no evidence that this is effective in reducing transmission, there is mechanistic plausibility for the potential effectiveness of this measure."

So, although the WHO found "no evidence" that masks "reduce transmission" of influenza, the WHO still recommended use. Go figure. 

2. CDC -- "little evidence to support use of face masks by well persons to avoid infection."

The CDC is less optimistic. In its most recent influenza mitigation guidelines (2017), the CDC only recommends face masks "by ill persons when crowded community settings cannot be avoided" and only during "very severe to extreme pandemic." For those who aren't sick, "CDC does not routinely recommend the use of face masks by well persons in the home or other community settings as a means of avoiding infection during influenza pandemics."

Why? Because of the data. "...[A] systematic literature review of 12 articles on face mask use found a substantial gap in the scientific literature on the effectiveness of face masks to reduce transmission of influenza virus infection." How about wearing masks to Wal Mart? "[T]here is less evidence that face masks are effective in natural settings, including community settings such as households, schools, and workplaces."

All this is why the U.S. Surgeon General, at the very outset of the COVID crisis, tweeted...

"Seriously people- STOP BUYING MASKS! They are NOT effective in preventing general public from catching #Coronavirus."

Of course, he's been panned for that tweet. But he was correct, based on the scientific data. And unless we accept the unproven proposition that COVID is fundamentally different from every other pandemic virus, he is still correct.

+ +And then there's cloth masks...

What about those "cloth masks" that are the height of virtue signaling. There is no data confirming the efficacy of cloth masks. None. Nonetheless, your CDC -- in its commitment to pure science -- provides complete instructions for DIY cloth face masks (with very helpful, cartoonish pictures), including instructions for something called the "Quick Cut T-shirt Face Covering (no sew method)", again, all in the interest of pure science. (And, of course, virtue signaling. Because if we don't have any scientific evidence, we can at least virtue signal with our self-made QCTSFC.)

Deadly pandemic. No evidence that masks work. But we'll provide cartoonish instructions so you can make your own. Oh the irony. If you missed it, we can't help.

And if you dare, here's the data...

Resources:

• (CDC) Community Mitigation Guidelines to Prevent Pandemic Influenza — United States, 2017
  • "Additional personal protective measures that might be recommended during pandemics include voluntary home quarantine of exposed household members and the use of face masks in community settings when ill. "
  • CDC Recommendation for Use by ill persons: "CDC might recommend the use of face masks by ill persons as a source control measure during severe, very severe, or extreme influenza pandemics when crowded community settings cannot be avoided (e.g., when adults and children with influenza symptoms seek medical attention) or when ill persons are in close contact with others/"
  • CDC Recommendation for Use by well persons: "CDC does not routinely recommend the use of face masks by well persons in the home or other community settings as a means of avoiding infection during influenza pandemics except under special, high-risk circumstances." (note: high-risk circumstances note are pregnant women or those in close contact with ill people).
  • In "very severe to extreme pandemic": "CDC might recommend use of face masks by ill persons when crowded community settings cannot be avoided."
  • More from the supporting CDC technical paper:
    • "there is less evidence that face masks are effective in natural settings, including community settings such as households, schools, and workplaces. Three randomized, controlled trials – in which masks were worn by a household’s index case, by healthy household members, or by all members of an affected household (54) – found little or no effect on disease spread."
    • "...a systematic literature review of 12 articles on face mask use found a substantial gap in the scientific literature on the effectiveness of face masks to reduce transmission of influenza virus infection. The review concluded that there is some evidence to support use of face masks by ill persons to protect others, but little evidence to support use of face masks by well persons to avoid infection. A second review of 17 articles reported that “none of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection”

• (WHO Official Guidelines) Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza
  • Released September 2019 (.pdf here)
  • "Ten RCTs (randomized controlled trial) were included in the meta-analysis, and there was no evidence that face masks are effective in reducing transmission of laboratory-confirmed influenza. "
    • "There is a moderate overall quality of evidence that face masks do not have a substantial effect on transmission of influenza."
  • Cloth face masks: "Reusable cloth face masks are not recommended."
  • Medical face masks: "Medical face masks are generally not reusable, and an adequate supply would be essential if the use of face masks was recommended. If worn by a symptomatic case, that person might require multiple masks per day for multiple days of illness."
  • WHO Recommendation
    • "Face masks worn by asymptomatic people are conditionally recommended in severe epidemics or pandemics, to reduce transmission in the community. Disposable, surgical masks are recommended to be worn at all times by symptomatic individuals when in contact with other individuals. Although there is no evidence that this is effective in reducing transmission, there is mechanistic plausibility for the potential effectiveness of this measure." (emphasis added)
• Facemasks and similar barriers to prevent respiratory illness such as COVID-19: A rapid systematic review
  • Julii Suzanne Brainard, Natalia Jones, Iain Lake, Lee Hooper, Paul Hunter, University of East Anglia (04/2020)
  • "The evidence is not sufficiently strong to support widespread use of facemasks as a protective measure against COVID-19. However, there is enough evidence to support the use of facemasks for short periods of time by particularly vulnerable individuals when in transient higher risk situations."
• (CDC) Interim Guidance for the Use of Masks to Control Seasonal Influenza Virus Transmission
  • CDC; last reviewed 5 March 2020
  • For symptomatic or infected "during periods of increased acute respiratory infections in the community": "Masks should be worn by these patients"... "until they are isolated in a private room"
  • asymptomatic persons: "No recommendation can be made at this time for mask use in the community by asymptomatic persons, including those at high risk for complications, to prevent exposure to influenza viruses. If unvaccinated high-risk persons decide to wear masks during periods of increased respiratory illness activity in the community, it is likely they will need to wear them any time they are in a public place and when they are around other household members."
• Face masks to prevent transmission of influenza virus: a systematic review
  • Cambridge University Press, 2010
  • "Our review highlights the limited evidence base supporting the efficacy or effectiveness of face masks to reduce influenza virus transmission."
  • "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 [7], 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.
• Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures (CDC Website, May 2020)
  • Jingyi Xiao, Eunice Y. C. Shiu, Huizhi Gao, Jessica Y. Wong, Min W. Fong, Sukhyun Ryu, and Benjamin J. Cowling, University of Hong Kong
  • "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."
  • "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."
  • Surgical masks: "There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure. Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza."
• Masks Don't Work: A review of science relevant to COVID-19 social policy
  • Denis G. Rancourt, PhD, Ontario Civil Liberties Association
  • "No RCT study with verified outcome shows a benefit for HCW or community members in households to wearing a mask or respirator. There is no such study. There are no exceptions. Likewise, no study exists that shows a benefit from a broad policy to wear masks in public."
• Use of cloth masks in the practice of infection control – evidence and policy gaps
  • University of New South Wales (June 2013)
  • " Currently there is a lack of evidence on the efficacy of cloth masks. "
  • "There is currently a concern that cloth mask use may give users a false sense of protection in the absence of proven efficacy that will encourage risk taking and/or decrease attention to other hygiene measures."
• Seriously people -- STOP BUYING MASKS!
  • Here's what the U.S. Surgeon General tweeted on February 29, 2020: "Seriously people- STOP BUYING MASKS! They are NOT effective in preventing general public from catching #Coronavirus, but if healthcare providers can’t get them to care for sick patients, it puts them and our communities at risk!"
  • This post linked to the CDC COVID guidelines, which after that post, of course, have been updated to encourage everyone to wear cloth masks:
    • "Everyone should wear a cloth face cover when they have to go out in public, for example to the grocery store or to pick up other necessities."
      
  • And of course, even though there is NO DATA on the efficacy of cloth face masks, your CDC -- in its commitment to pure science -- then provides complete instructions for DIY cloth face masks (with very helpful, cartoonish pictures), including instructions for something called the "Quick Cut T-shirt Face Covering (no sew method)", again, all in the interest of pure science. (And, of course, virtue signaling. Because if we don't have any scientific evidence, we can at least virtue signal with our self-made QCTSFC.)