Physical distancing, face masks, and eye protection

The Lancet Voice chats with Holger Schünemann and Derek Chu, authors of new research on physical distancing, face masks, and eye protection, to find out the best approach to these vital virus control methods.

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Transcript

This transcript was automatically generated using speech recognition technology and may differ from the original audio. In citing or otherwise referring to the contents of this podcast, please ensure that you are quoting the recorded audio rather than this transcript.

Gavin: Hello, welcome to another special COVID 19 episode of The Lancer Voice. I'm Gavin Cleaver. 

Jessamy: And I'm Jess Bagenal. 

Gavin: Today we're talking about the effectiveness of physical distancing and personal protective equipment. And this is off the back of a new systematic review and meta analysis that we're publishing.

So Jess, this is a review of every available study looking at Transmissibility of coronaviruses. So that's sars, mers, and Covid, right? 

Jessamy: Yes, that's right. And it's a systematic review. So that just means that there's a sort of set method for which people search through all of the literature that's out there and they collate all of that.

And then they do a meta analysis, so they look at the quantitative data and try and come up with some conclusions from it. This was commissioned by the WHO and what's amazing is quite how quickly this was produced and the sort of global teamwork that occurred in sending things around to other people in other time zones.

So it's a huge piece of work and one that sheds a lot of light onto our understanding. 

Gavin: Yeah, we're very lucky to be able to talk with a couple of the authors so maybe we'll hear you interviewing them and then we'll have a quick chat about the conclusions. 

Jessamy: That sounds great. So Holger and Derek, perhaps you could start by just telling us a little bit about where you work and what your roles are.

Holger: So I'm Holger Schoonemann. I'm a professor at McMaster University. I'm a clinical epidemiologist, so I practice internal medicine and focus on knowledge synthesis in my research. I am director of Cochrane Canada, which is relevant here probably, and I co chair something that is called the Great Working Group.

Derek: I'm Derek Chu. I'm also at McMaster University. I am both a general internist as well as a clinical immunologist and allergist. I work with Holger very closely in performing knowledge synthesis as well as Moving forward with studies like such as this where we were able to work also with the WHO to put together some new findings.

Jessamy: That's great. And these are such important findings. You've written a great manuscript for us about personal protective equipment and social distancing and the effects that this has on the spread of COVID 19. Perhaps you could tell us a little bit about the origins of the study and what led to it.

Holger: We for a really long time, for over 15, close to 15 years, we've been working quite closely with the WHO, the World Health Organization. We have a collaborating center for infectious disease. research methods and recommendations and have been involved in some rapid guidance development for what at that time was avian influenza.

And ever since I've worked quite closely and with the World Health Organization on older synthesis and the WHO has approached us to conduct a urgent systematic review. That is a synthesis of the best available evidence. On a given topic on this particular topic, and that is how face masks potentially protect against COVID 19 infection.

Related to that was a review on physical distancing as well as protection. of health care workers when they wear eye protection. That came to us at the end of March. 

Jessamy: And face masks as part of personal protective equipment kind of falls under that group of devices and equipment that we use in health care that we use so frequently that actually there doesn't seem to be much evidence behind it.

Things like plasters, bandages, cannula, things that we use in the millions and yet there isn't a kind of strong evidence base for it, what's the kind of different types of masks that we're looking at in this situation? 

Derek: So when it comes to the different types of face masks, there's a, there is a wide variety.

The most commonly used are in the community setting thoughts about cotton or gauze face masks, which are, can be homemade. Then in the healthcare workers saying, Increasingly, there are thoughts about the differentiation between masks and respirators masks being those that are typically surgical or medical masks, which we most commonly see.

And then in terms of respirators, there are a number of different types, which in North America, typically referred to as N95. 95 referring to the filtration efficiency or capacity of the actual device. There are also other respirators which are powered, which may have an even higher rating or effectiveness.

Holger: And I would perhaps just add to that in particular the context of the N95. mask or respirator, there are different international, first of all, terms for that, although the masks seem to perform relatively similar. So in North America, as Derek indicated, N95 is a term that is utilized and it goes back to a certification by the National Institute of Health and in the U.

S. In Europe, the term FFP2 is used. In China, where many of our masks are coming from KN95 is utilized and those three types of masks are fairly similar in their performance based on what we know, but those are the more sophisticated, I would put in quotation marks. masks that appear to have better filtration the three types being fairly similar.

There are, again similar, different terms used for a similar type of mask in other jurisdictions. Japan and Korea, for instance, have yet other terms for those type of masks. 

Jessamy: And Holger, what about the eye protection, which you also looked at? What do we mean by eye protection? 

Holger: Yeah, eye protection also comes in very different shapes and forms, unfortunately, also in, in the studies that we look at.

So obviously there are goggles goggles close the, hopefully close the eyes up entirely. There is in particular in the healthcare setting, sometimes concerns around fogging of these types of eye protection, but face shields that are plastic shields that can either be attached to a mask or can be entire, entirely separate face shields, typically plastic shields are what we would have considered in this analysis.

So shields, for instance, that start at your forehead and cover the entire face basically come down over your eyes, over your nose and mouth that hopefully are already covered by a face mask. 

Jessamy: Because this is something that we do use a lot in healthcare anyway, why isn't there evidence at the moment?

Because there's been so much mixed messaging up to this point about whether masks are useful or not in the community setting. What's your understanding of why we are in this position of uncertainty? 

Holger: It's a combination of things. So first of all, what typically happens is that there's many research studies conducted.

Some of them are very well done. Others are not so well done. And Oftentimes we, it's too challenging to synthesize all of the evidence, all of the studies that are actually out there. And what then happens is that we might rely on study findings that best fit our preconceived notions and promulgate those findings as opposed to saying, okay, we really need to look at all of the research that is out there and try in an unbiased fashion, first of all, synthesize it and focus on the best available evidence here.

And you're right. It is somewhat surprising that there are not many more better or really well done randomized controlled experiments of different types of masks and of masks, although some of them are available. Some randomized trials are available. It is surprising that there are not more, but what we were able to do here is we were able to synthesize.

Many non randomized studies that we carefully looked at and appraised for how biased they potentially might be by standing for how systematic deviation from the truth, or how much a deviation from the truth might exist in the findings. And look at those studies the best available studies.

in this context and try to really bring them together. So there are studies or all of them that we included are not randomized controlled experiments, but many of them are what we would consider well done observational studies. We brought them together. So now I think we have a really good basis to go from.

Obviously future research will inform this further. 

Jessamy: And they are all studies that are on coronaviruses. 

Holger: Yes. So what we did here, In correspondence with the WHO and in agreement with the WHO and the experts there, as well as other experts, we looked at the three related coronaviruses. There are obviously many coronaviruses, but the three that we believe have caused let's say the biggest health impact are those that have caused SARS in the early 2000s MERS, so the Middle Eastern Respiratory Syndrome.

And covid 19. So what we did is we looked at these three related viruses and obviously the impact of physical distancing and mass and eye protection on infection with those three. So there was a degree of extrapolation necessary because the evidence at the time or at the current time. is still somewhat limited.

So we focused on these three related viruses because it is believed that at least in terms of transmission, they are fairly similar. 

Jessamy: And Derek, perhaps you could tell us what the sort of main findings of the study are with regard to face masks and eye protection. 

Derek: As Holger mentioned, by looking at all the available data in an unbiased way and synthesizing it together, we found first that, that masks in general, Associated strongly with protection from transmission of virus from an infected individual to those that are in close proximity to them, whether that be in the health care worker setting or in the community setting.

Even though there is the possibility that the effect or the how protective mask use is would be stronger or larger in the health care worker setting, that it still is significantly protective. in the community setting. In addition, we evaluated the possibility that respirators or N95 or FFP2 respirators are all more effective than simple surgical face masks by using a technique called Bayesian meta analysis, whereby we were able to integrate All available information, including what few randomized trials were available.

And we did find that the findings overall supported the fact that respirators were more effective than medical masks in protecting against transmission of virus. When it came to physical distancing as well as eye protection, both of these were strongly protective against transmission of virus. as well with physical distancing measures increasing in their association with protection with each meter of distance additional.

Jessamy: Just moving on to physical distancing then, what were the types of studies that you looked at to get those results and to appreciate? What effect physical distancing might have? 

Derek: So across all they included studies, which were 44 non randomized studies, including about 26, 000 individuals, of which six and a half thousand were actually COVID 19.

We observed that some of the studies used different cutoffs for what they would constitute as their risk for actually developing transmission of virus. Some would use direct physical contact, others would use a one meter distance, and still others would use a two meters distance. Across all the studies, there was a highly strong protective effect of being at least one meter distance away.

And when we then evaluated the variability of those cutoffs using a technique called meta regression, we were then able to find that each one meter additional distance, the relative degree of protection then increased about two fold. That is to say, the relative effect between zero and one meters increased twofold.

And again, the relative protective effect between one and two meters again increased twofold. Which overall supports physical distancing measures of at least two meters when feasible and possible. And that this may also have significant implications for how we define what exactly a close contact constitutes.

These also have implications then on how to perform contact tracing, as well as modeling for future preparations of pandemic response efforts. 

Jessamy: So what you're saying is that if somebody came into contact with another person that was more than a meter, then you may not need to contact trace them? 

Derek: This has been, there have been some variability in exactly how individuals define what is the distance that puts someone at risk.

And this is the fundamentally the question of contact tracing. We want to trace and follow those individuals that would be at highest risk. And there have been variability across the globe about should be a one meter cutoff, should be a two meter cutoff. By performing this quantitative analysis, what we're able to show is that individuals even at two meters away are at risk.

And so this does then raise the question of, should we have a uniform standard of contact tracing within two meters, for example, rather than just one meter. 

Holger: So our data supports it to be two meters rather than one or 1. 5 meters. If that interpretation was made more over, I think in particular working in non metric systems, it's not six feet.

6 feet is not 2 meters, 6 feet is actually 1 meter 83 and given what Derek mentioned that there seems to be a relation between the distance and the effect this should be either 6 12 feet or 7 feet even, which is closer to 2 meters. And while there seems to be a subtle difference, it is based on this data it is suggested that there is a difference.

Jessamy: Thanks for clarifying that, Holger. What are some of the implications of the protective equipment point of view? With regard to face masks, I was particularly interested by this concept of sort of the need for face masks and therefore healthcare workers necessarily not being able to get access to them.

Particularly at the moment, people are being asked to reuse masks or change them. What does the evidence from this study suggest about those sorts of practices? 

Derek: There are a few points to discuss about this, particularly because of some of the challenges with supply. The overarching theme that I'd like to reinforce is that when it comes to evidence based medicine, evidence alone is never enough.

And so even though we need to integrate the best summaries of the available evidence, we also need to be able to integrate factors that are contextual, acceptability, feasibility, values, and preferences. And so To the first point, the evidence to date when it comes to medical masks versus no medical masks or respirators versus medical masks has been highly debated.

And at this time, our synthesis provides much needed clarification as to the best available evidence for The current global pandemic of COVID 19, both showing that medical masks versus no medical masks as well as respirators versus medical masks are both highly effective in both community as well as healthcare worker settings.

However, we also reviewed in over 24 studies, the contextual factors that might influence clinical recommendations and policies. Regarding how to implement these if possible. Now, a number of qualitative studies have shown that the use of masks can be quite acceptable at both health care workers and the public, particularly around epidemics.

And so we may well be seeing a new normal of what some have called quote unquote masking or the frequent use of masks, even in the non health care worker setting. And the second is that despite being able to be more protective, respirators do have to be thought carefully about supply chain, about negative effects such as facial skin breakdown and discomfort, which may undermine their effectiveness if frequently removed or manipulated.

In the current state, when there is a lack of supply. We have to think about the rational use of face masks in those areas at highest risk, as well as how do we optimally deliver or produce such highly effective respirators. And in the discussion, we comment that there have been some calls for repurposing of manufacturing capacities or government directed instructions to increase the production of 

Holger: such respirators.

evidence about the effects of an intervention. Is typically enough to make a decision. We are also focusing on other evidence in the context of evidence based medicine in particular. Other evidence that relates to as Derek indicated, acceptability of an intervention. There's evidence about that and we included that evidence here.

The acceptability, for instance, relating to having to. Walk and work all day with a mask if you're working in a health care setting. So I'm just on clinical service and I can tell you that having a mask on your face for the whole day, my colleagues feel the same way, is not very comfortable and It clearly interferes with communication and other issues.

That evidence about the acceptability is really important in terms of formulating policy in that context. At the same time, although it's described as a new situation it's a new situation for us a hundred years ago after the Spanish flu. Face masking was policy and mandatory in many jurisdictions.

So this comes back and cycles through society I believe over time. But as a bottom line, it looks like N95 or FFP2 or KN95 masks are more protective for healthcare workers, possibly also the public, Just regular face masks and it's really important that that we supply healthcare workers with the best intervention that is the best possible mask and gearing up production is extremely important from our point of view in this context.

Again, this is an interpretation of the studies that we have here. But this is what the evidence right now suggests from our point of view. 

Jessamy: And along those lines, I was interested by this concept of layering when people might be trying to make their own face masks at home or maybe, trying to cover their face in any way.

What did you find about that? 

Derek: In both comparing within the individual studies compared the different types of available face masks and other studies didn't, but they, we were able to compare between studies to answer this question. And essentially, there is a relative hierarchy that could be generated whereby very simple face masks being single layer paper masks or single layer cotton masks are at the bottom.

Then, next come multi layer cotton or gauze face masks. This is by multi layer, we mean the best studied being 12 to 16 layers. In the available evidence that we were able to pull together, and this seemed to be comparable to surgical or medical face masks. And then after this came respirators, such as N95 respirators or powered respirators.

Now, this is based off of the available information for which this is the best suggestion at the time. And we do await ongoing randomized trials for direct information relevant to this. But these will not yield results for months, if not years. 

Jessamy: So Holger, perhaps you could just round that up for us in terms of the bottom line.

What's the sort of thing that people should be considering if they're trying to make their own face masks or wear some kind of masks at home? 

Holger: So first of all, follow good instructions that are coming from, I would say, official authorities in terms of producing your own face masks. And based on what we are seeing here, it is likely that wearing a face mask when you have contact with others is going to protect you, the more we go up that hierarchy that is, in other words, going up to N95 respirators, there may be additional effects, but it looks like having a self made face mask is definitely better than having no face mask.

Jessamy: That's great. Thank you both. So for me, some of the most interesting things from that conversation was this sort of highlighting the fact that really there needs to be a change for health care workers, that they need to be able to wear respirators in all health care settings because that is going to make a big difference to how many health care workers are infected and to the sort of levels of risk that they're exposed to.

That was really interesting for me and also this idea of homemade face masks and the different number of layers that may benefit people. 

Gavin: So there's a big difference between respirators and normal masks, right? Which they emphasized. 

Jessamy: Exactly. So respirators are really designed to remove some of the aerosols, the viral particles in the air.

Whereas face masks are a much more kind of basic thing, which, as they say there, you might be able to make at home. The key there. is that there is some really solid evidence for physical distancing. We've heard a lot in the news recently about, two meters not necessarily being just a number plucked from the air.

Here, we see quite solid evidence and, I think the authors were very keen that we just reiterate again that these are estimates and these are the sort of best available evidence that we have at the moment and it's very much a changing field. But that two meters, seven foot is a minimum that is going to provide you with some safety.

Gavin: Right, of course, and it's all done on a kind of continuum, isn't it? Obviously, the safest distance would be many meters away. But it's good to have this available evidence for, For such an important thing that has such a huge effect on people's lives, because like you said, the research before was quite spotty, and based on some very old studies.

Jessamy: Exactly, it's always the case with these things which we use so often, like face masks, actually they never really get the kind of Concentration and emphasis that they need because they're not really thought of as particularly exciting. But then you, we find ourselves in these kind of situations and we suddenly need, some robust evidence about what people should be doing.

I think one of the sort of interesting things about this is also the sort of hierarchy that no one intervention is going to protect you. But that by adding these different sort of parts of protection, physical distancing, eye protection. and masks, that really you can get to somewhere where people can feel quite safe outside in the community, doing what they need to do.

And that obviously has huge implications for how we start to try and open things up and get back to normal in the absence of a vaccine. 

Gavin: Absolutely. Although it should be said on the other hand, if you're two meters away from your friend in the park, you probably, eye protection and a surgical mask is probably overkill.

Jessamy: Exactly. And you are going to look a little bit strange as well. 

Gavin: Having all this information from this meta analysis is great, but perhaps, Jessamy, what we need is some randomised controlled trials as well. 

Jessamy: Exactly. This is a lot of evidence over a long period of time, very different types of studies.

And what we do need are those very controlled trials that look at two different parts of an intervention and control for baseline characteristics very carefully. so that we can get more of an idea about what it is that's working and what's not working. But at the moment this is the best available evidence that we have and it should provide some clarity and insight for everybody really in how we go about our daily lives.

Thanks for 

Gavin: listening to The Lancet Voice. If you have any feedback we'd love to hear it. You can contact us at podcastatthelancet. com And our archive of special COVID 19 episodes and all our other episodes is available on Apple, on Spotify, and wherever you normally get your podcasts. See you again next time.