Why masks don't protect against COVID-19: the evidence on the use of surgical masks to prevent infections during surgery

Mar 16, 2024

Several arguments are commonly provided to justify masking recommendations despite the lack of credible data (discussed at length in previous posts on this Substack). One of them is that surgeons and doctors mask, and since surgeons and doctors must know what they are doing, masks must work.

This argument is wrong for several reasons. First, it is an appeal to authority. And the authority of physicians is by no means infallible. In one study examining all randomized controlled trials testing established medical practice published in the New England Journal of Medicine in 2009, 16 of 35, or almost half, were shown to be ineffective or harmful [1]. In another study, this time examining all articles in the New England Journal of Medicine published from 2001 to 2010, 146 of 363 of randomized controlled trials examining standard of care treatments showed these treatments to be ineffective or harmful [2]. Current untested medical practices, at least as of 2010, were nearly as likely to be ineffective or harmful as they were to be beneficial.

Moreover, although a symbol of surgery, for more than half a century research has shown that surgical masks have no impact on wound infection during surgical procedures. In one study from 1975, researchers assessed microbiological contamination of an eight-room operating room suite; it was concluded that the presence of people were the overwhelming determining factor of bacterial contamination and that “the wearing of a surgical face mask had no effect upon the overall operating room environmental contamination and probably work only to redirect the projectile effect of talking and breathing” [3]. In another study from 1981, researchers found that their rate of infections actually significantly decreased when the surgeons in their study stopped using surgical masks [4], a finding that later researchers attributed to the redirection of bacteria out of the sides of the mask and into the wound [5]. Another study from 1989 found that there was no difference in infection rates in catheterization patients when physicians were wearing masks and caps versus not wearing them [6]. A study in 2002 reaffirmed this conclusion [7].

A 2001 review strikingly came to the conclusion that “the evidence for discontinuing the use of surgical face masks would appear to be stronger than the evidence available to support their continued use” [8]. A systematic review from 2009 concludes: “From the limited randomized trials it is still not clear whether wearing surgical face masks harms or benefits the patients undergoing elective surgery” [9]. A 2010 statement from the Karolinska Institute put things: “When introduced a century ago, the purpose of the surgical facemask was to provide protection for the patient from surgical wound infections. But is there evidence that face masks prevent wound infections? A recent review concluded that it is not clear whether face masks prevent surgical wound infections, and the scientific evidence for this practice is weak and insufficient” [10]. A 2014 review of the trials investigating masks during surgical procedures found that: “no statistically significant difference in infection rates between the masked and unmasked group in any of the trials” [11]. A 2015 review concluded that “there is a lack of substantial evidence to support claims that facemasks protect either patient or surgeon from infectious contamination” [12]. And a 2002 Cochrane systematic review and meta-analysis of three trials and 2113 participants found that “There was no statistically significant difference in infection rates between the masked and unmasked group in any of the trials” [13]. Updated versions of this review from 2014 [14] and 2016 [15] came to the same conclusions.

The story of masking among surgeons is an excellent one in demonstrating that plausible theories do not always translate into effective practices.

Although it was once thought that surgical masks could stop droplets from the oral cavity from traveling onto the patient and increasing rates of infection, new ideas based on the evidence have revised this understanding. It has been shown, for instance, that masks create friction and cause the falling of skin cells directly onto the surgical field, potentially making the problem of hygiene worse than it would have been without a mask. To test these competing theories, tests in a clinical trial setting must be conducted to show that the theory in question actually impacts the outcome in question (infection rates). As yet, these tests have not shown the benefit of masks, and indeed, surgical masks might indeed in the final analysis turn out to be mildly detrimental. Or mildly beneficial. We don’t know.

None of this implies that surgeons should necessarily stop masking. I certainly would not feel altogether comfortable if my surgeon decided not to mask; but I wouldn't feel entirely uncomfortable, either, since the studies do show that the difference from the practice is small to the point of being undetectable.

This case study does show, however, that we cannot always trust our guesses: we need evidence. It also shows that masking among surgeons to prevent surgery-related infections is by no means a powerful argument for masking among the community to prevent COVID-19 infections. After all, among surgeons compliance to masking is perfect and occurs throughout the entire surgery, and masks most certainly do block bacteria from the oral cavity, and yet still no impact on infection is seen among surgeons who mask versus those who go maskless. In contrast, among the general population, masking compliance is imperfect, people still must remove their masks for eating, etc., and masks most certainly do not block virus particles anywhere near as effectively as they block bacteria.

If there is not measurable impact of surgeons masking on the infection rates during surgery, then we would certainly not expect to see an impact on rate of respiratory virus infection from community masking. (Which is exactly what we see in the clinical trial data for masking against respiratory viruses.)

It turns out, therefore, the data on masking for surgeries actually is a strong argument against surgical masks being effective against respiratory viruses. And in order to know that, we needed to look at the data, not make assumptions. There's a lesson there.

Dr. K

Kevin, Marvelous summary of something about which I have been lecturing for decades. Masking was the original fraud that enabled all the others. I spoke stridently against it in the beginning (my videos on N95 leakage are priceless) and have never stopped -- not that it has made any difference.

But you are right -- the "why would surgeons wear them unless it were important?" line is ubiquitous and then the eye rolling when it is pointed out that it is traditional, like wearing clerical robes, not useful. So your succinct summary with references is a marvelous contribution. I have already spread it around widely.

Thanks for doing this. Know you have been abused, but love to see the phoenix rise up from the ashes.

Expand full comment

1 reply by Kevin Bass PhD MS

Apr 29, 2024

Kevin, Love what you are doing. I am a hematologist, medical school professor, entrepreneur. I will be glad to send you a video snapshot that makes it all clear, but even that piece is 30MB. If you can figure out how to get you 30Mb, it's yours!

1 more comment...

Forbidden Science

Discussion about this post