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Mask Science – The CDC’s House Built On Sand


Philip Buckler



Philip is a General Dentist (DDS). He graduated from the University of Detroit Mercy School of Dentistry in 2010. He is currently on activy duty in the Army, however he is doing appearances only as a civilian.

Digging into the references cited by the CDC exposes just how outrageously weak the evidence base supporting compulsory facemasking truly is.


The two CDC references most frequently cited to support the use of facemasks as a measure to control the spread of SARS-CoV-2 and justify mask mandates are their online publications “The Science of Masking to Control COVID-19” (November 2020) and “Science Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2” (as of this writing, last updated in May 2021). When pressed to produce some kind of scientific evidence to support their invasive mask requirements, public health officials, politicians, and educational supervisors alike will often simply point to these documents as though they need no further justification.  


Between them, these two CDC publications cite 68 separate references (69, if you count the fact that one of them cites the other). In addition to thoroughly reading these CDC publications, I have personally acquired and read every single one of the 68 other studies they reference - including those which are not in English (hurrah for Google Translate).


At least 12 of the 68 references cited by the CDC – including the only two randomized controlled trials the CDC mentions – turn out upon close interrogation to constitute evidence against the efficacy of facemasks (which the CDC implicitly acknowledges by attempting to discredit their results).


11 of the remaining 56 citations are not even studies which directly support the efficacy of masks to mitigate viral spread, but simply provide background information which would support the use of masks if they worked. For example, arguing that masks have minimal side effects, or that speech produces aerosols. [1, 2]


As for the remaining 45 citations, let me break them down for you:


·        5 Modeling (i.e. Conjecture) and Expert Opinion – the weakest form of evidence

·        24 Mechanistic and Laboratory Studies – the second-weakest form of evidence, which needs to be confirmed by real-world data before being acted upon

·        15 Observational Studies – uncontrolled associational studies using a wide range of methods

·        1 Meta-Analysis of observational studies [3]


No evidence is worthless, but the CDC fails to cite even a single randomized controlled trial, much less a meta-analysis of randomized controlled trials, to support the efficacy of facemasks in mitigating the spread of respiratory viruses. This is because there are no such studies which definitively support their position.  


In fact, the CDC’s “Science Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2“ devotes considerable effort attempting to explain away the results of just two randomized controlled trials [4, 5] which provide strong evidence that masks are not effective (and – in the case of the 2015 MacIntyre study – that cloth masks are very likely to have a net detrimental effect even in the best-case scenario of being worn by trained healthcare workers and washed daily). If, however, the CDC’s objections to Bundgaard and MacIntyre’s studies were applied consistently to their own sources, they would have to throw out most, if not all, of the studies they rely on the justify recommending the use of facemasks (I will cover this in more detail in a future post).


What the CDC does not include in their analysis, however, is the most telling. They outright ignore more than 80 studies, including multiple randomized controlled trials, which provide direct, strong evidence (or at least stronger than the studies cited by the CDC) that masks do not work to mitigate the spread of respiratory viruses.


The CDC makes a great effort to build the strongest case they can for the efficacy of facemasks to control the spread of respiratory viruses. On close inspection, however, their case falls apart like a house of cards, and quite frankly borders on lying by omission. Neither of their most commonly-referenced publications provides sufficient evidence to clear the empirical – never mind the moral – hurdles necessary to justify compulsory masking even in medical settings, much less the public at large.


When put under a microscope, the CDC’s “The Science of Masking to Control COVID-19” (November 2020) and “Science Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2” (May 2021), provide an excellent illustration of just how flimsy and deficient the evidential base underlying compulsory masking truly is.


1.            Asadi, S., et al., Aerosol emission and superemission during human speech increase with voice loudness. Scientific Reports, 2019. 9(1).

2.            Chan, N.C., K. Li, and J. Hirsh, Peripheral Oxygen Saturation in Older Persons Wearing Nonmedical Face Masks in Community Settings. Jama, 2020. 324(22): p. 2323-2324.

3.            Chu, D.K., et al., Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. Lancet, 2020. 395(10242): p. 1973-1987.

4.            Bundgaard, H., et al., Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers : A Randomized Controlled Trial. Ann Intern Med, 2021. 174(3): p. 335-343.

5.            MacIntyre, C.R., et al., A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. BMJ Open, 2015. 5(4): p. e006577.


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