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Hong Kong Experts: Are Masks an Independently Significant Coronavirus Intervention?

A letter-to-the-editor published in the American Journal of Respiratory and Critical Care Medicine highlights a pattern in which countries that emphasized face-mask adoption early on in the SARS-CoV-2 pandemic had milder outbreak burdens. The letter was written by experts from Hong Kong.

"In many Asian countries like China and Japan, the use of face masks in this pandemic is ubiquitous and is considered as a hygiene etiquette, whereas in many western countries, its use in the public is less common,” the authors wrote.

The Hong Kong researchers used online searches to quantify public interest in mask usage. Among the 42 regions examined across 6 continents, a lower number of daily cases correlated with high mask-related internet search volume in several areas of Asia.

In a press release, Sunny Wong, MD, associate professor, Department of Medicine and Therapeutics, The Chinese University of Hong Kong, noted the particular success of Hong Kong in the pandemic despite many social distancing measures being voluntary.

"Despite [Hong Kong's] proximity to mainland China, its infection rate of COVID-19 is generally modest with only 1,110 cases to-date. This correlates with an almost ubiquitous use of face masks in the city (up to 98.8 percent by respondents in a survey). Similar patterns are seen in other Asian areas, such as Taiwan, Thailand and Malaysia,” Wong said.

The authors noted that the correlation appears independently significant, after adjusting for searches of related terms around hand washing and social distancing, as well as government policy responses.

Authors expressed uncertainty on precisely how much the public’s wide adoption of masks compared, in terms of infection control import, with other measures. But the pattern they identify lends confidence to the hypothesis that face masks are an important and independent means to flatten the curve despite situations where close contact is inevitable.

Given the inherently temporary nature of social buy-in when it comes to the strictest level of stay-at-home orders, expressed in anecdotes about partying and so-called COVID fatigue, measures such as mask (or face-shield) mass distribution could be an important part of a responsible and adaptive "reopening."

"We believe that face mask use, hand washing and social distancing are all important components of the non-pharmaceutical measures against COVID-19,” Wong remarked.

Related Coverage

Universal Face Shields: A Better Option for COVID-19 Containment?

Segment description: 
Michael B. Edmond, MD, MPH, MPA, MBA, associate chief medical officer, chief quality officer, and clinical professor of infectious diseases, University of Iowa Health Care, discusses a viewpoint he and colleagues published in JAMA on the universal adopting of face shields to help cut the transmissibility of COVID-19.

Interview transcript (modified slightly for readability):

Contagion®: Your article asks the question, "Can we reduce COVID-19 transmission in the community by universally adopting face shields in addition to existing interventions, such as testing, contact tracing and hand hygiene."

So, why a face shield?

Michael B. Edmond, MD, MPH, MPA, MBA: That's a good question. We first addressed this inside the hospital. This started several weeks ago as we started to look at all of our plans for COVID. And what we realized was the supply chain for face masks is quite compromised because most of the factories that make medical-grade face masks are in China. They've been impacted by the outbreak and were shut down. So we were concerned that we might not be able to make it through the outbreak having enough face masks and so we started to look at face shields to see if we could get them. What we found is that because they're used in other industries, they were available and we were able to source them and bring them into the hospital. Within a few weeks, we were able to have every person in our hospital in a face shield, both those seeing patients and those who aren't seeing patients.

We learned a lot about face shields in that implementation because we implemented somewhere between 13,000 and 15,000 face shields in a relatively rapid period of time. Then I started to think about whether this might be something that we could do in the community. Part of the problem we have again in the community is if we're going to ask people to wear face masks, which CDC has now asked them to do, again, we don't have good supplies of medica-grade face masks and people, therefore, are having to wear cloth face masks. We know from the medical literature that cloth face masks are inferior to medical-grade face masks. They probably do provide some protection...but but probably not where it needs to be. We started to think more about whether face shields might be an alternative in the community setting.

Contagion®: What is the benefit of a face shield over a face mask? Do we have any evidence that supports the effectiveness? 

Edmond: In terms of effectiveness, with this particular virus, we don't have evidence yet. I think we can infer from what we know about influenza, in which there are simulation studies that show very significant decreases in contamination of a person when droplets are coming at them when a face shield has been used at about 18 inches. It's about a 96% reduction, so it's very, very good. That's only with 1 face shield—a face shield on the receiver end. But if everybody is in face shields, you have both source control and protection of the susceptible person, and so we would envision that the effectiveness would even be better in that situation.

Contagion®: What about the whole production supply chain aspect of this? We do hear all about the shortages of medical masks and other personal protective equipment. You're saying we wouldn't run into those issues with face shields? How can we leverage some of the existing supply chains if we were to universally adopt these?

Edmond: One of the great things that's happened is that a number of large manufacturers have been able to retrofit their production lines to produce facials. So for example, Apple and Nike, john deere, GM, they're all now making face shields. And there are a host of smaller companies that are doing it as well. Even though that's not their normal business. They're producing these and selling them. So it's actually you know, and I keep an eye on this, because I have an interest in it. It's relatively easy to be able to find a fish yield if you want to get one.

Contagion®: They're also reusable. 

Edmond: Many advantages, one is the fact that they're durable. The standard medical mask has a finite lifespan. Once they get wet from the exhaled air, they lose effectiveness, they start to degenerate, they're not made to last. On the other hand, a face shield is a durable piece of equipment because it's primarily made of plastic. The other great thing about it is you can you can clean them in between uses, so you could just wash them off with soap and water or any kind of household disinfectant that you might have. Another great advantage of them over face masks is that they prevent you from touching your face. One of the things we know about face masks is that some people will begin to touch their face more to try to adjust the mask. That's exactly what we don't want because if your hands are contaminated with a virus, then you're going to auto-inoculate yourself potentially touching your nose or your eyes or mouth, and give yourself the virus. The face shield, and I've done this firsthand now wearing face shields in the hospital when I'm seeing patients, is sometimes your face will itch and you go to scratch it, and you realize there's a shield there and you can't touch your face. So that's one of the great benefits of wearing a face shield.

Contagion®: I imagine there're also some social aspects to it. A face shield doesn't impede those social interactions as much as a face mask in terms of stifling vocalizations or even covering up expressions.

Edmond: Right, so facial expressions, you can still see. You can see people's lip movements, which helps with speech perception. One of the things that my wife, who's an oncologist, talks about is how difficult it is to have important conversations with patients about prognosis or end of life, those kinds of things, when you're wearing a face mask where it is a barrier to communication. I think the face shields a little easier from that standpoint, definitely.

Contagion®: I guess the million dollar question is how do we convince people to wear these? We seem to have a hard enough time convincing people to practice social distancing.

Edmond: Yes, or even washing their hands. All of these health-related behaviors, I think, take some time. It's interesting to me that, even though we haven't been dealing with COVID for that long of a period of time, I think people are changing their behaviors. I can see it every day when I go out to take a run in my neighborhood. If there's another runner coming in the opposite direction, one of us will cross the street so that we're not close to each other. I think you're seeing more people wearing some type of face covering when they are going, for example, to the grocery store. I think they are more cognizant of hand hygiene. I think it's happening, but I think with any health-related behavior, it's not something that happens instantaneously. It takes a lot of practice for us to be able to do it.

Contagion®: Do you see society being able to possibly reopen or get to a "new normal" sooner if we added face shields?

Edmond: That's our hypothesis. Our hypothesis is that if every person were in a face shield, the transmission of this virus would go down. We think we would be able to decrease the R0 to less than 1. In that case, we would be able to open up society sooner because we're able to use some other adjunctive means to social distancing to getting that transmissibility down.

Contagion®: If we were to universally adopt face shield, that could incorporate some sort of policy decision from a government standpoint. What about convincing the government or leaders who can make those types of decisions? 

Edmond: I think that the issue now is, and I think we're seeing this, is the difficulties of doing what we're doing now, which is to keep people sheltering in place, restricting their movement. Those are hard things for our society to grapple with. If we're able to use something as simple as a face shield to allow society to to relax some of these more difficult things, then it might be an easy sell because I think people would see the benefit of that.

Contagion®: Have you received any feedback on your piece since it was published?

Edmond: We've received feedback from a lot of people, some people very supportive of it. Some people concerned about infectious aerosols. One of the things we talked about in the viewpoint is that, at least at this point, the evidence suggests that the primary mechanism of transmission is droplet and not aerosol. And of course, the face shield is great for droplets to catch all those droplets on the shield. If there's aerosol transmission, then the shields wouldn't be as good. But again, we think by having both the susceptible person and the infectious source in face shields, even that aerolization will be markedly decreased and there's nothing to prevent people from putting a mask on underneath the face shield if they want to do that. Anyway, so I think that the feedback that we've received is sort of what we've expected. We see people on both sides of the argument.
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