There is considerable debate in the public sphere about whether or not we should be wearing masks to help prevent the spread of COVID-19, and for good reason. We have no large prospective trials that have clearly demonstrated the efficacy of mask use in slowing a pandemic spread. The scientific literature that does exist reveals mixed results, although I think it provides some support for the occasional use of masks in our current predicament.
I’ll come back to the why you might consider wearing a mask, and the scientific evidence for and against it, in a bit. I want to first focus on a more important issue, which is how you should wear a mask. From what I’ve seen in my community in the past few weeks, this is information that is sorely needed.
How To Wear A Mask
I’ve been wearing masks for over three decades in my work. I think the reason we surgeons wear masks is the same reason you might consider wearing one; to protect others more than yourself. How we wear them, however, is even more important. We don’t wear them all the time, but for a specific circumstance, and only for the time needed.
When I get ready to do a procedure, the first thing I do is put on my mask. Next, I cleanse my hands, don my gown and gloves, and then perform the procedure. After I am done, and dressings are in place, I remove my gown, gloves, and mask. I then cleanse my hands again.
In our communities, we should take the same approach. Wear a mask for a defined purpose, like going to the store, and then remove it. Cleanse your hands after putting on your mask, and again after removing it. For a disposable mask, you should use it only that once, and wear a new one the next time. For a cloth mask, you should also use it only that once, and wash it before next use.
I never touch my mask during a procedure. You shouldn’t touch your mask when wearing it, either.
I commonly see employees wearing masks around their necks, only to raise them over their faces when dealing with a customer. Similarly, customers frequently lower or otherwise adjust their masks when in a business. This repeated touching defeats the purpose of wearing a mask in the first place. Any viral particles you might be exhaling are embedded in your mask, and have now been transmitted from your mask to your hands, where they will then pass to anything you might touch.
Wearing a mask when not in close proximity to others, when physical distancing is easy to maintain, is probably of no value, and might even be harmful. This includes when driving your car or going for a walk. Masks, especially fabric ones, fairly quickly become saturated with water vapor from the mere act of breathing. They also get saturated with whatever microscopic critters you might be exhaling, and then inhaling again.
If we limit the times when we feel a mask might be of value, such as going to a store, and in turn limit the frequency of those types of activities, we should be more able to adopt good “mask discipline”. Put it on, cleanse your hands, do your business, remove and dispose of your mask (or put it in a plastic bag for later washing), and again cleanse your hands.
Why To Wear A Mask
The main argument usually given for wearing a mask in a community setting is the same reason why I wear one in my clinic, to protect others. There may be some protective benefit to the wearer, but it will be limited unless the mask is of surgical grade or higher, such as an N-95 mask, and is properly fitted and worn.
The CDC somewhat flip-flopped on the issue of wearing mask in a community setting, while the WHO has reportedly held fast in recommending against their use. In fact, the recommendations from the CDC and WHO are actually pretty consistent. The CDC doesn’t recommend wearing masks in all circumstances, and the WHO recognizes there may be value in wearing masks in some circumstances, although it still doesn’t advise wearing them in general community settings.
We now know from recent studies that a significant portion of individuals with coronavirus lack symptoms (“asymptomatic”) and that even those who eventually develop symptoms (“pre-symptomatic”) can transmit the virus to others before showing symptoms. This means that the virus can spread between people interacting in close proximity—for example, speaking, coughing, or sneezing—even if those people are not exhibiting symptoms. In light of this new evidence, CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission.
Wearing a medical mask is one of the prevention measures that can limit the spread of certain respiratory viral diseases, including COVID-19. However, the use of a mask alone is insufficient to provide an adequate level of protection, and other measures should also be adopted. Whether or not masks are used, maximum compliance with hand hygiene and other IPC measures is critical to prevent human-to-human transmission of COVID-19.
However, there is currently no evidence that wearing a mask (whether medical or other types) by healthy persons in the wider community setting, including universal community masking, can prevent them from infection with respiratory viruses, including COVID-19.
Why Not To Wear A Mask
As already noted, the scientific evidence of the efficacy of wearing masks to slow the spread of a pandemic is sparse. And, as I’ve also previously pointed out, not using good “mask discipline” may negate any possible beneficial effects of your mask, and might even be harmful to you and others. Equally importantly, wearing masks could create a “moral hazard”, promoting less safe practices in other areas, thinking we are more protected by our masks than we actually are.
Finally, and I must concede that this is a fair point, the mandate by many businesses for the wearing of masks by customers is a bit of “safety theater”, comparable to the “security theater” of TSA agents at airports. It may make people feel more comfortable, but seeing the poor “mask discipline” at many businesses, I acknowledge this may be more of “feel-good” practice than a real benefit, at least as currently practiced.
The use of medical masks in the community may create a false sense of security, with neglect of other essential measures, such as hand hygiene practices and physical distancing, and may lead to touching the face under the masks and under the eyes, result in unnecessary costs, and take masks away from those in health care who need them most, especially when masks are in short supply.
Show Me The Science
There are hundreds of scientific studies that have evaluated the effectiveness of wearing masks in preventing viral spread, either to the user, or from the user to others. I’ve read a few dozen, and have included eight recent reports that I thought were particularly notable at the end of this post.
I suspect most of my readers will only have a glancing interest in any of these, so I’ll first provide a few general media review articles which discuss the issue of the efficacy of masks, both for and against.
Wired, April 2020
The recent back-and-forth debate—and policy reversal—over the use of face masks to prevent the spread of Covid-19 reveals a glaring double standard. For some reason, we’ve been treating this one particular matter of public health differently. We don’t see op-eds that ask whether people really need to keep 6 feet away from each other on the street, as opposed to 3 feet, or that cast doubt on whether it’s such a good idea to promote bouts of handwashing that are 20 seconds long. But when it comes to covering our faces, a scholarly hyper-rigor has been applied. In recent weeks, experts have counseled caution—or rejected the use of masks by the general public outright—as they pleaded for better, more decisive evidence. Why?
They’re right, of course, that the research literature on mask usage doesn’t provide definitive answers. There are no large-scale clinical trials proving that personal use of masks can prevent pandemic spread; and the ones that look at masks and influenza have produced equivocal results. But this smattering of evidence doesn’t tell us much, either way: The trials neither prove that masks are useful, nor that they’re dangerous or a waste of time. That’s because the studies have been both few in number and beset with methodological problems.
New Scientist, April 2020
But what about the rest of us? In an attempt to answer this question, Paul Hunter at the University of East Anglia, UK, and his colleagues looked at 31 published studies on the efficacy of face masks.
Overall, the evidence suggests there may be a small benefit to wearing some kind of face covering. They do seem to prevent sick people from spreading the virus, but the evidence is weak and inconsistent, says Hunter.
“Our view is that there was some evidence of a degree of protection, but it wasn’t great,” he says. “So we still don’t effectively know if face masks in the community work.”
Hunter thinks there is enough evidence to support mask-wearing for some frontline staff, such as those working in public transport or supermarkets, as well as vulnerable people who temporarily enter high-risk environments like hospitals – as long as their use doesn’t deprive healthcare workers of equipment.
Live Science, April 2020
The bottom line, experts say, is that masks might help keep people with COVID-19 from unknowingly passing along the virus. But the evidence for the efficacy of surgical or homemade masks is limited, and masks aren’t the most important protection against the coronavirus.
“Putting a face mask on does not mean that you stop the other practices,” said May Chu, a clinical professor in epidemiology at the Colorado School of Public Health on the Anschutz Medical Campus who was not involved in either new study. “It does not mean you get closer to people, it does not mean you don’t have to wash your hands as often and you can touch your face. All of that still is in place, this is just an add-on.”
Medical News Today, April 2020
Based on the current findings, co-senior author Prof. Benjamin J. Cowling — also the co-director of the World Health Organization (WHO) Collaborating Centre for Infectious Disease Epidemiology and Control — notes that surgical masks could play a role in fighting the COVID-19 pandemic.
“The ability of surgical masks to reduce seasonal coronavirus in respiratory droplets and aerosols implies that such masks can contribute to slowing the spread of COVID-19 when worn by infected people,” says Prof. Cowling.
However, the researchers emphasize that for members of the public, masks should be the very last protective measure in the context of the current pandemic.
Medium, April 2020
Like handwashing, face masks can only offer partial protection against Covid-19. The best defense right now is exactly what we’re being told to do by the experts — completely avoiding exposure to the SARS-CoV-2 virus through social distancing. So long as you’re staying home and nobody else in your home has been exposed to the virus, you should not wear a face mask.
However, some of us currently live with sick family members, and the rest of us will eventually need to come out of hiding. Based on the research, face masks are much more likely to help than to hurt. Even if it’s just a homemade cloth mask, if you wear it correctly and avoid touching it, the science suggests that it won’t hurt you and will most likely reduce your exposure to the virus.
For you masochists, here follow the eight scientific studies I promised. Also as promised, they’re a mixed bag. As mentioned, I reviewed a few dozen, and these are just the ones I found interesting from one point of view or another.
Some suggest a protective value to the wearing of face masks, and some don’t. Some even suggest the possibility of harm.
Only one of the studies directly evaluates the effectiveness of masks on COVID-19. Only two studies compare cloth masks to surgical masks. The one study that did evaluate the effectiveness of cloth masks against COVID-19 showed no benefit compared to surgical masks, but had only four study participants, and didn’t have a no-mask control group.
Honestly, this is the norm for much of scientific research. It doesn’t definitively answer the questions we want to ask much of the time.
Even in my practice of medicine, much of what I’ve done over the decades is not firmly established by scientific studies. We do what we’ve been taught, what seems to have worked in the past, and keep doing so until some new research tells us to reconsider.
That’s just the reality of medicine and science. We deal in uncertainties just as much as everyone else. With that perhaps depressing thought in mind, I wish you my very best.
Emerging Infectious Diseases, February 2009
Design: Randomized controlled study of adult members of households in Australia during the 2006 and 2007 winter influenza seasons, in which a child from the household had presented with an influenza-like illness (ILI). A variety of different viruses were detected in most children, with Influenza A being the most common. The 145 adults were randomized to either surgical masks, P2 masks (the Australian equivalent of the N95), and no-mask control groups.
Findings: There were no clinically significant differences among the three study groups in the incidence of ILI in the adult household members. However, compliance with mask use was less than 50%, and among adults where were adherent to mask use, there was a statistically significant reduction of ILI.
Caveats: No comparison between cloth and surgical masks. Evaluation limited to household exposure, not community exposure.
Notable: High incidence of noncompliance with proper mask use.
Journal of Infectious Disease, February 2010
Design: Randomized controlled study involving 1437 college students living in residence halls during the 2007 H1NI Influenza pandemic. Lasted six weeks, and students were randomized to one of three groups; one wearing surgical masks and using hand sanitizer, one wearing surgical masks only, and a control group.
Findings: No reduction in the cumulative incidence of influenza-like illness (ILI) over the entire course of the study; but, during weeks 4 through 6, there was a statistically significant reduction in incidence of ILI among the mask and hand sanitizer group. Face mask use alone also showed a reduction in incidence over this same time period, but it did not reach statistical significance.
Caveats: No comparison between cloth and surgical masks. Possibly not directly comparable to a general community setting.
Notable: Arguably shows the benefits of hand hygiene over mask use, at least for influenza.
The Cochrane Database of Systematic Reviews, July 2011
Design: Review of 215 studies of mixed design, of which 67 were chosen for analysis.
Findings: There are a lot of findings given 67 studies evaluated. For surgical mask use specifically, and without regard to the study design or the type of environment in which the masks were worn, masks were judge effective in 13 studies, ineffective in 4 studies, and found to cause harm in 1 study.
Caveats: No comparison between cloth and surgical masks.
Notable: This study has been updated several times since 2007, each with the same title, and this is the most recent version I found.
British Medical Journal, April 2015
Design: The first randomized controlled trial comparing cloth masks to surgical masks. It involved 1607 study participants from 14 different hospitals in Vietnam.
Findings: The use of cloth masks resulted in an increased risk of infection among the mask wearers compared to the use of surgical masks.
Caveats: No comparison between cloth masks and a no-mask control group. Only looked at primary infection rates among mask wearers, not secondary transmission to others. Focused on medical workers in hospitals, not the general public in community settings.
Notable: Per the authors, “moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection”
Epidemics, September 2017
Design: Review and meta-analysis of 16 studies of variable design conducted during the 2009 H1NI influenza “swine flu” pandemic.
Findings: Regular hand hygiene provided a statistically significant protective effect. Mask (surgical or N95) use did not provide a statistically significant protective effect.
Caveats: No comparison between cloth and surgical masks.
Notable: The authors point out, as do some other authors, that quantifying the degree of mask usage (always, sometimes, rarely) would be helpful in assessing protective effect, but this is infrequently done in many studies.
Annals of Internal Medicine, April 2020
Design: A study of patients with active COVID-19 infections, directly comparing cloth and surgical masks with a no mask control. Four patients with COVID-19 were studied, and each was asked to cough 5 times over petri dishes while wearing no mask, a surgical mask, and a cotton mask. The petri dishes, and the inside and outside surfaces of all masks, were tested for the presence of COVID-19.
Findings: Neither type of mask prevented transmission of SARS-CoV-2 to the petri dishes. High concentrations of viral particles were also found on both the inside and outside surfaces of both masks (slightly higher on the outside, oddly).
Caveats: Very small sample size, consisting of only 4 participants. Tested only during coughing, not normal respiration.
Notable: The fact that significant amounts of virus were found on the surfaces of both types of masks indicates that the masks do stop some virus, even if not a statistically significant amount in this study. Also, individuals wearing masks should be cognizant that virus will accumulate on the outside of their masks, so repeated touching of masks is not desirable.
Nature Medicine, April 2020
Design: A study specifically evaluating the effectiveness of surgical masks in reducing viral transmission. Consisted of 246 individuals with an acute respiratory illness, 123 of whom tested positive for a specific virus (mostly rhinovirus and influenza, and a few seasonal coronaviruses). They tested for viral particles from exhaled breathing over 30 minutes, with or without the subjects wearing a mask.
Findings: Mask use “significantly reduced detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets”. They did not find a statistically significant reduction in rhinovirus detection in either aerosols or respiratory droplets.
Caveats: No comparison between cloth and surgical masks.
Notable: An interesting sub finding of this study was the fact that a large proportion of subjects had undetectable viral shedding in exhaled breath for each of the three viruses, and particularly for influenza and coronavirus. Per the authors, “this might imply that prolonged close contact would be required for transmission to occur”.
medRxiv, April 2020
Design: A review of 31 relevant studies, to include 12 randomized controlled trials, and including a meta-analysis of 28 of those studies. It looked specifically at the use of a “face barrier” (primarily facemasks, but also face shields and goggles) in community settings, as opposed to hospitals or clinics.
Findings: A slight, but statistically insignificant, reduction in primary infection rates among mask wearers, and a modest, but also statistically insignificant, reduced risk of secondary transmission to others. This latter effect was stronger if both infected and well persons wore facemarks, rather than if only well people wore them.
Caveats: It has not been officially peer-reviewed by other researchers. No comparison between cloth and surgical masks.
Notable: Per the authors, “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.”