Coronavirus (COVID-19): Press Conference with Joseph Allen, 07/21/20

You’re listening to a press conference from the Harvard T.H. Chan School of Public Health with Joseph Allen, assistant professor of exposure assessment science in the Department of Environmental Health and director of the Healthy Buildings Program. This call was recorded at 12 p.m. Eastern Time on Tuesday, July 21st.


JOSEPH ALLEN: Thanks, everyone, for joining in these. I really appreciate, first, that our school does this and also that we have eager reporters who are interested in talking to the scientists to get this message out, particularly around schools. And maybe I’ll just start there. Keep my remarks brief. Reopening schools should be a national priority. I don’t think we’ve been treating it as such at this point, reopening aspects of the economy that are less central to our core function as a society, which first and foremost, I believe is educating the next generation. I’m dismayed at the lack of priority at this point. And at the same time, our team has put out a 60 page report on risk reduction strategies that schools can and should implement to get kids and teachers back safely. I’m happy to answer questions on schools, but of course, any of those topics and I’m glad Nicole mentioned that my recent op-ed, you know, despite all the bad news we have lately, there are some positive signs and it’s a good reminder that science is working and there are some things in the near term that give me hope.

MODERATOR: Great. Thank you, Dr. Allen. I will also say it’s not just science working, it’s a lot of scientists out there, too. First question.

Q: Thank you so much. I actually have two questions, if that’s OK. The first one, I was wondering if you could talk a little bit about the role of air conditioning systems and whether or not they facilitate the spread of the coronavirus, especially with cases surging in the South, students potentially returning to schools in August. Is this a concern, given what we’re learning about airborne transmission? And if so, are there ways to make them safer?

JOSEPH ALLEN: Yes, a great question, and I’ll preface this by saying I was one of the 239 scientists that wrote the letter to the WHO, urging them to recognize that airborne transmission is happening. I wrote my first piece on airborne transmission and healthy buildings as the first line of defense against novel coronavirus in late January and published in the Financial Times in early February. So we’ve known about airborne transmission for a long time. I think I’ve been writing about it every week or two. I wrote an article in the Washington Post at the end of May, linking airborne transmission and super spreader events. So, one of the reasons my field got together to write that joint article because the WHO and CDC failed to recognize airborne transmission, at least explicitly. They’ve implicitly been saying it.

It’s nothing to be feared, it just means that we have to recognize it’s happening so we can apply the appropriate control strategies. And I can talk about those. I had a book come out in April called Healthy Buildings. We’re talking about the basics of healthy building strategies here that work for COVID-19, but also a whole host of other infectious diseases and the other exposures to indoor pollutants. But let’s talk about your question about air conditioning. There’s nothing inherently wrong about air conditioning. It’s just when it’s done poorly that it’s a problem. So let me say that a bit better. If you have air conditioning in any building, let’s say your home and it’s a window air conditioner. It’s possible that you’re only recirculating that air. And in that case, indoor pollutants build up, be it, chemicals that off gas from carpet, or someone who is sick and shedding virus when they breathe or cough or sneeze. So the problem is not as though the air conditioner, the problem is under ventilation. Sometimes if you have one of these window units, people seal it up, fill up the rest of the house, and don’t let the building breathe. So in a commercial building or a building with a central air conditioning system, those have fresh outdoor air delivery coming in. The amount of fresh outdoor air varies. So there are minimum standards. They are minimums, they are not usually sufficient. They should be increased. We’ve been advocating for that since February. Any air that is recirculated should go through a higher efficiency filter, a merv 13 or higher.

If you have air that’s only being recirculated inside, you want to supplement that. For example, in a house where you had a room air conditioner, you could use a portable air cleaner with a HEPA filter to clean the air indoors, and it would help remove airborne particles, including airborne viral particles. So big picture, air conditioning in and of itself is not the problem. It’s the fundamental fear of you want to increase the amount of outdoor air so you’re diluting indoor contaminants and you want to filter any recirculated air. Now, we don’t know this for sure, but it has been a concern in the summer months, as you were seeing these outbreaks in the south. When it gets hot and humid, people spend more time indoors and they seek out cooler temperatures with air conditioners. So, if air conditioners aren’t being operated in a correct manner, and it’s not the air conditioner, if you’re only recirculating air, you need to deploy supplemental air cleaning technologies like portable air cleaners.

Q: Great. Thank you. Then my second question is also sort of on the topic of returning to school settings or the office, but also at home. How important is disinfecting our surroundings, when it comes to infection prevention? And with so many cleaning aisles still empty or picked over now, months into the pandemic, what should people be doing to clean their homes, offices or classrooms?

JOSEPH ALLEN: That’s a good question and maybe we’ll take it a step higher, because we talked about airborne transmission. If we think about moments of transmission in that line of control, that will help inform this conversation of that question. So we’ve covered airborne transmission. Here you’re talking about contaminated services or what we call fomites. And then you have close contact transmission. Close contact, we address by physical distancing, mask wearing. Airborne, we address through engineering control. 

Fomite transmission is contaminated surfaces, and the most effective way to break that chain is frequent hand-washing. In addition, we try to clean and disinfect surfaces. And that’s more important in places that have a lot of people or commonly and frequently touch surfaces like shared doorknobs or things like that. But if you think about what we’re doing, the cleaning, disinfecting, it’s really difficult to clean and disinfect enough. You could imagine, in an office building, let’s say, and everyone’s going through it all the time. Well, you to really eliminate the hazard, you’d have to clean, disinfect every single time someone touch something. Well, that’s not practical. It’s not feasible. And also, it’s not the right strategy. The better strategy is when people come into the building, they wash their hands and use hand sanitizer. Throughout the day, they do that. That’s a better control strategy. I’ve seen many organizations, and you see the run on materials at the grocery store, cleaning, disinfecting all sorts of surfaces all day long, you know, 24/7, even if people aren’t using the space. And that’s not really a sustainable strategy in terms of being able to keep that compliance. Also, the more effective strategy, like I said, is just hand washing frequently.

Q: Thank you so much.

JOSEPH ALLEN: Thank you.

MODERATOR: Next question.

Q: Hi. Thanks for taking my question. You mentioned physical distancing and of course, that has a lot to do with opening schools, going back to workplaces and shopping. We’ve got two different recommendations, one from the CDC and one from WHO. WHO has three feet or more, CDC has six feet or more. Could you talk about the scientific evidence that allows these two different estimates? And which one, but based on the science behind it is right and why?

JOSEPH ALLEN: Yes, a really great question. There is confusion out there. There are two different, let’s call them standards for lack of a better word. And you ask about the science. So the science, there’s no bright line. Three feet, six feet. There’s no bright line to cut off. But here’s what is driving that to a sense. It’s basic aerosol physics that when I talk or breath or cough, I will omit a range of aerosols, everyone will. Aerosols are just airborne particles of different sizes. Very large particles will settle out due to gravitational forces, quickly. And the idea is that within three feet or six feet, a lot of these settle out. The reality is many of these, well, they change their size over time as they dehumidify in the air. Some will float for 30 minutes. The smaller aerosols will float for hours indoors. And that’s airborne transmission. So, it’s not a bright cut off. It’s not like at six feet, everything drops or at three feet, everything drops off.

So let’s start, first of foremost, everyone should be wearing a mask for that reason, so you control the source and you can help filter some of that that’s coming in to you, if you’re wearing it, if someone else is sick in your presence. Two, in general principles, more distances, better than less. You can think about this in terms of, you know, if you can smell someone’s breath, it’s too close. The further away you’d smell less, and if you are further away, you don’t smell it at all, as a way to kind of gauge, well, how does distance matter? Or some people use the thinking about someone smoking. So, if you’re really close, it’s intense, three feet away it’s less than ten, six feet, even less. If you’re at the other end of the room, you might smell it, but depending on the ventilation, the room may not smell at all. Smoke is an aerosol. So there’s not a bright line.

It is good from a public health standpoint that the public in the US has gravitated around the six foot distance thing. I think that’s important to have a target and a goal. Now, as it relates to schools, I think it’s also really important that we put it in the context of kids in particular. And we know a couple things about kids, that, at least from my standpoint in Massachusetts, this idea that we can get to three feet physical distancing in schools is sufficient. So kids are less likely to get this virus than adults, and they’re less likely to suffer severe consequences. The evidence looks like they’re less likely to transmit it, particularly those who are young. So in that context, and recognize that other controls need to be in place like ventilation, filtration and mask wearing, against the wider risk of not having kids in school, supports my position that the three foot physical distance thing is acceptable in schools.

I think some of the challenges I’m hearing with the schools conversation is the detachment of the wider conversation about risk. So very often, we have a conversation about risk in the classroom, without the context of larger risk to students holistically. The risk of not being in classroom are also quite large. We have to include that in this risk benefit equation. Thinking about all the other controls and the disease dynamics for kids, in coming up with that opinion or position that three foot physical distancing is OK in the classroom. I hope I answered your question. It’s not as simple as it seems, it seems like a discrepancy, it is. But in terms of how you apply that to decision making, particularly in the schools context, we have to take a wider lens and think about risk and exposure holistically and think about the different demographics or age groups too.

Q: The aerosol question factors into that as well, I would imagine.

JOSEPH ALLEN: In terms of distance?

Q: Right.

JOSEPH ALLEN: Sure. So here’s a misunderstanding about aerosols and airborne transmission. When people think of airborne, they think of long range airborne, which is true. If you have low ventilation, you have someone who is sick in a room, the concentration of viral particles can build up and you can have long range airborne transmission. The reality is, though, your risk is higher, even from airborne transmission at close distance. So, if you and I are three feet away and I’m sick, you’re at a higher risk for breathing in more, even the small aerosols at that close distance, I think that makes sense. They disperse over time and space in the room. So, airborne transmission is not just long range. It’s a bit of a semantics thing for people in my field and infectious disease epidemiologists.

If you’re in close contact with someone, I think the public just says, OK, being closer is more risky than being further away. And there is some science on how much of the close contact risk is a result of large droplets, meaning the ones that actually project out and land in your eye or your mouth versus the tiny aerosols that flow past your your breathing zone at a high concentration and then disperse. So, the science, we’re still working all that out. But, from a public and control standpoint, it doesn’t really matter, it’s the distancing thing helps reduce that overall risk. What fraction comes from droplets or technical aerosols? That’s a scientific debate. I’m happy to talk about it more, but it’s also gets into the weeds. From a control standpoint, it doesn’t really influence the conversation.

Q: Thank you.

MODERATOR: Next question.

Q: Hi. Thank you, Dr. Allen. You had a recent opinion piece in the Boston Globe saying schools should reopen in person. Well, I have a couple of questions related to that. Was that intended for Massachusetts? Would you say the same for Texas? Why or why not? We have soaring cases here, very high levels right now. And also, would you please talk about the difference between masks that cover the face directly, the kind we all are wearing now, and face shields, as for both source control and protection for the wearer, please.

JOSEPH ALLEN: Sure. Yeah. Nice question. I will say I wrote another opinion piece. This was in the Boston Globe. It has implications for Massachusetts, but I also think the principles hold for wider. I also wrote an opinion piece in The Washington Post a couple of weeks ago with a more national plan saying, yes, schools should open. The one in The Boston Globe was coauthored this week with three other faculty at the Harvard School of Public Health, with different backgrounds. But let me talk more broadly, conditions precedent, meaning things that have to happen before you can reopen schools. One is you have to have your cases under control. So, the decisions on whether or not to reopen are dependent on local conditions. So what’s happening in your region in Dallas, is different from where we are in Massachusetts. You’re experiencing more or less what we experienced back in March and April and a little bit of May.

Q: Would you consider us under control now or not? I mean, I would love to have some sort of number. I know it’s difficult to give numbers.

JOSEPH ALLEN: So I do think that there are other resources at our school and elsewhere, and I can point you to the Safra Center for Ethics at Harvard that has published guidance on external factors. So I’m going to leave that to the infectious diseases epidemiologist and I’ll talk about control strategies in the building that can be deployed.

I’ll say this, though. Everywhere in the country, we have to treat schools as the priority they are to open. I don’t see the seriousness by our national leaders or back regional leaders. We see reopening happening in all sorts of sectors of the economy. Well, you know, the economic crisis is a public health crisis. At the same time, we should be prioritizing getting kids back in school. What does it say about us as a society if we can’t get kids back into school because of the decisions we’re making in the rest of our economy? It’s a gross failing on our part. And I’ll be clear, this starts with the president of the United States who has failed to address this in a serious fashion starting in January, in February, in March. We bought ourselves time in March to flatten the curve. We squandered that in April and May. Same in June. And here we are in July.

It should not have been a surprise to anybody that we’d be having this conversation right now, thinking about how we’re gonna get kids back in school. Wasn’t a surprise school starts in August and September. And so why weren’t these conversations happening, as soon as we shut schools down in March, to figure out what are the steps we are going to take as a country to get our kids back to school. Kids out of school has devastating consequences that we’re not talking about in this conversation. We have virtual dropouts happening. In Boston, ten thousand high school kids didn’t log in in the month of May. In Philadelphia, fifty percent of elementary school kids made daily contact. Fifty percent. What are they doing all day? Where are they? We don’t know. I’ve had teachers write me asking that, saying “I’m concerned, I haven’t seen or heard from my students in months. If we don’t go back in September, I’m not going to hear or see from them again for many months.”.

We know that kids out of school are more sedentary, so they’re less physically active. Thirty million plus kids in this country rely on schools for their food, which is a gross problem in and of itself, and another gross failing. UNICEF has said kids who are not in school are more likely to suffer from abuse, neglect, exploitation and violence. So if we’re having a conversation about when to reopen schools, we need to be having that conversation in a larger context of risk and recognize that these are devastating consequences to keeping kids out of school. The decisions we’re making right now that keep them out of school are an absolute gross failing. I find it hard to comprehend that we’re okay with this as a country, that we’re having this conversation, that we’re going to keep kids out of school again because we can’t do the things we need to do to keep this virus in check that every other developed country has done.

I wrote an article in April with a colleague at Harvard Kennedy School, acknowledging that there was a plan to save lives in the economy and all we had to do is act on it. Myself, Mark Lipsitch, and several others at the Harvard School of Public Health put out a product called COVID Path Forward, in April, outlining 14 priority areas to save lives in the economy. Again, there was a plan and we failed to act on it. Here we are acting like we were surprised that kids had to be back in school in a couple of weeks. And it seems like the first time some people are even thinking about this.

Q: OK. Thank you. That’s all really helpful context. But I mean, can you or are you willing to make a recommendation for Texas? Given our high case loads here. And again, if you don’t mind, the mask versus face shields.

JOSEPH ALLEN: Yeah. So I think I’m going to stay with my answer there in that I’m wary of making statements on schools that don’t take the full context into account, because I’ve seen people do it, and I think it’s a mistake because we’re oversimplifying this complex problem and the complex cost or risk benefit analysis that’s happening. So on masks and face shields, let’s talk about the science there. Face shields can help block the large droplets as a physical barrier. They can be quite effective. They do not block aerosols. So, as we breathe or cough or sneeze, or anything else, the aerosols can get around the physical face shield, the Plexiglas face shield. It comes with the benefit of being able to see people’s mouth and you can communicate. But masks are preferred  for controlling the release of aerosols.

Q: Thank you.

JOSEPH ALLEN: Thank you.

MODERATOR: Next question. Her question is, can poor ventilation drive droplets released from sneezing and coughing, to evaporate into aerosols?

JOSEPH ALLEN: So, yes, there’s a couple of factors that influence aerosol. Again, it’s a continuum. As we breathe or cough, the size of the particles will differ. But also, we expel them as respiratory droplets. So the viruses, it’s never naked in the air. And the size of that droplet is going to change. So it starts to evaporate as soon as it leaves our mouth, and it’ll turn into a smaller, what we call, a droplet nuclei, which is a finer aerosol. So the factors that are going to influence the air quality, a lot of it is going to be the humidity in the space, the relative humidity. Typically for viruses, 40 to 60 percent relative humidity, we see is associated with less transmissibility. We don’t quite know the exact reason, but it’s probably related to these two factors. One is if you have humidity and the range of 40, 60 percent, less evaporation of the respiratory droplet happens, meaning it’ll settle out of the air quicker. It’ll be a heavier, bigger aerosol. And so if it’s drier, you evaporate it and you get a higher likelihood of having droplet nuclei which can stay airborne for longer periods of time. That’s on the source side. There’s also benefits to that mid range relative humidity in terms of receptor, meaning our lungs function better at that mid range humidity. So, your mucociliary action in your lungs is actually more efficient when it’s not dried out.

MODERATOR: Next question.

Q: Wonderful. Thank you for doing this. The CDC is now walking away from the test based method, meaning that there is no longer a need to have two negative tests in order for people to return to work, school, travel. Now, why is that? Is this good or bad for the workplace safety?

JOSEPH ALLEN: I can comment briefly on it, but I would point you to colleagues in our school that are deeply versed in this. And I want to be clear, I don’t know the rationale for CDC’s response. I will tell you that we know that you can get a positive test weeks after your infectious. So while I don’t know CDC’s rationale, there are examples, many examples where someone was sick with COVID-19, their symptoms have gone away, they have an antibody response, so in other words, there’s serological tests if the antibody test comes back positive, and yet their viral test also comes back positive. You’re still detecting some of the virus, but you’re no longer infectious. So for me, speaking just in broad terms, that’s something you have to be cognizant of when you’re trying to interpret a positive viral tests after symptoms. And so the companies I’ve been advising as they think about testing strategies to help them think through what that might mean if someone is really past the period where they’re infectious, but they still get a positive test, technically, according to the CDC’s past guidance, that would have meant one thing. But there’s a lot of nuance there. I would encourage you to, in particular, follow the work of Michael Mina in our school.

Q: I’ll do that right now. Thank you.

JOSEPH ALLEN: Thank you.

MODERATOR: Next question.

Q: Thanks again. This question is a more meta question, really. It’s about science and policy making. Is the science available to policymakers? Is all the science that is needed, available to them to make these decisions on distancing and other issues?

JOSEPH ALLEN: It’s a good question, and I guess two ways to interpret the question. One is, is the current science that we have and our current understanding of COVID available to them? Absolutely. In fact, that was one we wrote that letter to WHO and they acknowledged it. So they have all the information they need on aerosol transmission, aerosol physics and distancing. Do we need more science? Sure. But I would caveat that in this. Do we need more science to make informed decisions about control strategies in schools and offices? No. We already know a lot about how this virus is transmitted. And we know enough to take appropriate precautions. And we know what the precautions should be at this point. Will we learn more? Absolutely. Should we continue and strive to learn more? Yes, absolutely.

In terms of aerosol physics, we know a lot about how particles travel in air. Things we still need to know are things like the dose or the amount of virus that really sets off the cascade of immune responses that leads to the adverse effects in people. In other words, how much of the virus leads to what response and how does it vary by people? And how does it vary by age and gender and race and ethnicity? So we still need to understand all that. And we’re continuing to explore that. But in terms of what we need to know or what WHO or CDC need to know in order to make policy, in my opinion, there’s enough there out there already in the scientific literature.

Q: And it’s been out there since when?

JOSEPH ALLEN: On distancing or airborne transmission?

Q: Distancing.

JOSEPH ALLEN: Well, we’ve known this for a long time. I mean, it really gets into my field of exposure science, we think of exposure as a function of three things, really. Intensity, frequency and duration and also timing, meaning what age you are, let’s say, or when it happened. But in terms of the intensity of exposure, we know that distance helps for viruses that are transmitted through the close contact route. So for something that’s mostly airborne like measles, distance also helps, but there’s a lot more airborne spread. Going back to January or at least, in early February, I wrote a piece in the Financial Times that talked about those modes of transmission and these control strategies. So, we’ve known for a long time that to decrease the intensity of exposure is increased distance. I mean, that holds for cigarette smoke, and holds for chemical exposures and holds for infectious diseases.

Q: Thanks.

MODERATOR: Next question.

Q: I wanted to ask what your recommendations are for school buildings in terms of reopening and getting kids back to school. So, you know, schools have different budgets. They probably can’t do everything that everyone is recommending. I’m also curious what you would prioritize, especially if schools can’t do certain things, then what items, if a school cannot do, would you see as huge red flags? In terms of maybe parents shouldn’t be sending their kids to school, if the school hasn’t done a certain thing?

JOSEPH ALLEN: That’s a great question. And I want to be clear that when we say my opinion is we need to reopen schools, it’s not schools as usual. We need to have these risk reduction strategies in place. And we’ve been careful to make recommendations that nearly every building can put in place. And even, let’s take these healthy building strategies, recognize that some of these can’t do some. So we don’t just stop there. We say if you can’t do this, then do that.

So, for example,  I’ll take it higher and say these are the things that schools should be doing. We absolutely should be wearing masks in schools. We should be building in mask breaks so we don’t have mask fatigue. This can be time outdoors as mask-free, or time when you’re physically distant and no talking in the classroom like quiet reading time. Absolutely, frequent hand-washing. We advocate for wash your hands every time you enter and exit the classroom every time you enter and exit the school. Make it a part of the daily routine. I guess that gets to one of our top recommendations, that school should establish a culture of health, safety and shared responsibility. This doesn’t happen by accident. If you think about what happens, say, in safety meetings and real estate, every morning starts with a safety message and a safety meeting. I think that should be happening in schools, and it should be reinforced daily. I think the training should be happening right now with teachers, parents, and students on the basics of disease transmission and what these control strategies are. So we create this shared this culture of shared responsibility. I think that’s critical.

Getting back to kind of a more detailed risk reduction strategy. So definitely wearing a mask. Definitely washing hands. Absolutely looking at ventilation and filtration. So if you’re in a classroom, you want to be sure you’re bringing in as much outdoor air as possible. If you have a system that can’t do that or if you’re in a naturally ventilated space, you want to open up the windows, maybe put a box fan in the window to facilitate the movement of outdoor air coming indoors. Recognizing that it can be difficult for many schools to upgrade or enhance or properly commission their AC system for those that do have mechanical ventilation. I think every classroom should have a portable air cleaner with HEPA filtration in the room. These devices, if they’re sized correctly, can provide several air changes per hour of clean air. So you can imagine if we have three air changes per hour of air going through a HEPA filter, that means the air and the spaces being cleaned every 20 minutes. HEPA filters capture nearly all airborne particles.

I’m gonna take this another level. You know, the conversation about schools has shocked me a little bit and that it has started from a position of we can’t do this rather than, how are we going to do this? I think about what happens in health care where there was never a question. Well, we’re not going be able to treat patients. It was that we know we’re gonna have to do this, so let’s get clever and figure out how to do it. Same thing needs to happen with schools. So I don’t buy into this position that I hear a lot is we can’t do this right. There’s this roadblock after roadblock. And it’s funny we teach kids a growth mindset, but don’t seem to be doing this when it comes to schools, and there are these solutions that can be put in place right now. You know, is it asking too much to have a portable air cleaner in every classroom? I don’t think so. And here’s why I feel confident the position that if we have community spread under control and we put in this risk reduction strategies, we can get kids back safely. Again, not taking anything out of a larger context, but we have to rely on the science that shows kids are less likely to get this and less likely to suffer severe consequences. That’s first and foremost. Also, these strategies, hand-washing, mask wearing, ventilation, air cleaning have been shown to work. These are evidence based risk reduction strategies. They work in hospitals, high risk environments. Talk to any hospital infection control person to ask what the control strategy is to put in place. They can’t do physical distancing, good mask compliance, hand-washing and hospitals take care of their building systems and manage this.

So there are things we can do and need to do to put them in place. So far, it doesn’t seem we have the will as a society, a country. And very often it’s a recalcitrant position that just as well, you know, we can’t go back because this is not the way we’ve done it in the past. And if we do it the way in the past, it’s going to be higher risk. Well, we have to do things differently. And these strategies I’m talking about don’t necessarily have to take too much time or cost that much money to put in place.

Q: Great. Thank you so much. If I’m allowed to ask a follow up, it’s related, but not directly about school buildings. I just wanted to ask about our current understanding of whether kids, adolescents transmit the virus as much as adults. You know, there was word of the South Korea study recently, and I’m curious how you interpret that, how that should be appropriately interpreted? And, what sort of additional information do we need to be able to understand kind of a little more definitively whether or not kids and older kids, how much they do transmit?

JOSEPH ALLEN: Yeah, I’m glad you asked that question. You’re at, right?

Q: Yes.

JOSEPH ALLEN: Yes. So this is great. That study came out over the weekend and it tells us some really important information, but the headline that it got attached with was incorrect. The headline being that older kids transmit the same as adults. Unfortunately, that went everywhere, including, I’ve seen senators talk about it, I’ve seen people sending me emails, teachers saying, well, maybe you missed this study. And it’s really unfortunate. Many of us spent Saturday on social media rebutting that study and correcting even some scientists who took an early position, that that study actually showed that older kids transmit the same as adults and many have since reversed that interpretation. And I’ll explain why. But the problem is that in some sense, it’s too late. That message escaped and went everywhere. And the more nuanced scientific discussion that happened on Sunday into Monday, a small fraction of people actually saw, I guess it speaks to a larger issue of science getting out into the media without it being filtered through scientists carefully. Well, let me explain why.

When I first saw that study, there was a huge caution flag in one of the data points related to the older teens. It was an incongruent data point that didn’t quite make sense when I first saw it. Not saying the data are bad. When I first saw it, it was off. Something was odd about it. So much so that if a student had shown their data to me and circled this one outlier data point and said, Hey, this is the headline of my paper news article, I suppose we should be really careful and go back and take a closer look. And it turns out when you do you realize that the study had a methodological limitation, not a flaw, just a limitation, and that it couldn’t identify who the actual index case was, so it inferred it. But we’ve shown, and others have have detailed this, that it’s possible to mistake who was the first person to get it in the home. Everything else looks normal in terms of almost linear change, in terms of transmission as you go from young to old. And here’s why it was a big caution flag when I first saw it. The 0 to 9 year olds transmit less and the 20 to 29 year olds transmit less. And somehow the 10 to 19 year olds looked more like 70 year olds. That’s a giant caution flag. Well, how could that be? How could they not look like they’re more immediate peer age groups? Here’s the other thing that when you look at that study and the reporting that happened over the weekend, unfortunately, people only focused on one half of the data table, which really surprised me. The other half of the data, which looks at non household contacts, actually shows that age group has transmissibility that looks a lot like the 0 to 9 year olds. In fact, the numbers about almost identical.

So this is the kind of scientific conversation that’s happening behind the scenes, but it was well after the headlines were out. A more appropriate headline, if you look at the data, was that at a minimum, even if you accept that one data point that was incongruent, what that study showed is 0 to 9 year olds are two to three times as likely to transmit, as adults. Now, imagine that was the headline, it would’ve been quite different interpretation. And we had this conversation on this call about context. Before that study came out, I saw three really important questions about kids and this virus. Two were answered. And importantly, and I’ve mentioned it twice or I’ll do it a third time. They’re less likely to get this virus, we know that. They’re less likely to suffer from the adverse consequences, we know that too. An outstanding question was why are they less likely to transmit? And early evidence suggests that they were. And if you look at on balance, all of the data in the study from the South Korean CDC, it actually supports that conclusion.

So I’ll add one thing about this study is that it’s also a conditional probability. So let’s say you think that incongruent data point is right? You still have to talk about it in the context of the first thing I mentioned, which was kids transmit less. So even if 10 to 19 year olds transmit the same as adults. They’re less likely to get it. So that conditional probability, that nuance there, was also lost in the stories about that report. It’s a really good example of the news getting ahead of the science. Look, it’s a really important study, it’s a lot of great information. It just has to be taken in the context of all the other information we have about kids at risk. And unfortunately, the one headline was generated from one incongruent data point. But if you look at the totality of the data, including the methodology, it’s quite clear. But the headline was wrong.

Q: Great. Thank you so much. So would you say that we still need to learn more about transmission, or do you think it’s pretty clear that kids probably transmit less?

JOSEPH ALLEN: Well, I’m always going to say we need to learn more about transmission. I say it’s on. No one study answers it. And unfortunately, that’s one of the problems with the headline. Let’s say that data even were believable. It doesn’t answer the question and it’s not in the context of the other data points. It certainly doesn’t change my position on kids and risk in schools. In fact, it further supports that kids are less likely to transmit, it looks like, by a lot compared to adults. And there’s a mechanistic reason people have floated this. But if you look at why this might happen, more lung morphology is different in young kids. Their lungs are developing. We generate breath droplets deep in our in our lungs and the alveolar region, the bronchioles, and this is a less developed region in kids, so they produce less breath droplets. The type of droplets that turn into droplet nuclei and stay aloft. So is it biologically plausible that kids transmit less? Yes. Same with do kids get it less. We know that from the epidemiological evidence, what about mechanistically? We have a plausible reason for why that is. We know this virus attaches to the ACE2 receptor on cells, and kids have lower ACE2 gene expression in their nasal passage, meaning less opportunities for the virus to get a foothold in our cells in the nose. So it’s not to say that all of this answers everything, but if we start to look again at the totality of evidence of where this South Korea CDC study fits, the data supports that kids, particularly young kids, transmit less than adults and because they get infected less and then they transmit less, that conditional probability is quite interesting and important. So that study is is everywhere, but this nuances, if anyone wants to take that on as a story, it’s an important one to clear up. And there are a whole host of scientists, too, you could talk to.

Q: Thank you so much.

MODERATOR: Next question.

Q: And I promise this is the last one. It’s actually two questions. One is, Dr. Allen, when you walk into a building, say, a grocery store or a bank where there are other people. What do you do in terms of distancing? And then the second part of the question is, are you going into your lab and what do you do in terms of distancing there?

JOSEPH ALLEN: Good question. So first, I try to restrict my activities to things that are absolutely necessary. Let me tell you first on that, if I don’t feel well, which I’ve felt fine, but if I don’t feel well, I’ll stay home. Absolutely. Two, I try to restrict my travel or not travel. I guess going out to things that are absolutely necessary. So go to the grocery store pharmacy, check up at the doctor. That’s important. And when I do do it, I always wear a mask. Always wear a mask. And then do my best to maintain physical distancing indoors.

Q: How far?

JOSEPH ALLEN: Well, I try to maintain as much as possible. I’ve written before that a good strategy is to stay smart, stay home when sick, mask when out. Avoid large gatherings, refresh indoor air and ten feet is better than six. Meaning, I try to maximize that. When we think about exposure, remember that intensity factor and frequency and duration. So duration comes into this too. If I’m at the grocery store and I need to pass by someone in the aisle, you go past that person. The duration is really short. It’s infrequent. So that helps reduce the overall exposure. But do I wear, you know, a ring around me that with a six foot radius? No. I am respectful of other people’s space. I maintain it as much as possible. I don’t break the six foot barrier unless I’m going by somebody. And for a short time.

Q: Terrific. And are you going into your office?

JOSEPH ALLEN: Not right now, because I have a lab that can work remotely and we’re doing our part by staying out of the building, so an important strategy for buildings is densification, so reducing the number of people that are in these buildings. As Harvard has prioritized lab work in wet labs, it just helps support that. My team has, like everybody, I think, at Harvard has removed all operations that can be done remotely. And keeping them remotely. The question is, would I go back into my office building? The answer’s yes because I know Harvard has instituted a lot of, if not all of these healthy building and other control strategies that I’ve been writing about in terms of following the hierarchy of controls.

Q: Terrific. Thanks.

JOSEPH ALLEN: Thank you.

MODERATOR: Dr. Allen. I have one quick question. So you were talking about schools and what schools can do to keep kids safe. What can parents do to help kids stay safe, as well, in their schools? Are there things, supplies, that parents could donate to schools to help them in this in this mission to keep kids safe?

JOSEPH ALLEN: Yeah, I think one of the things they can do is start finding comfortable masks for your kids and get them used to the idea that they can be wearing masks for extended periods of time. That’s going to be different for a lot of kids. The comfort level of different masks is different, but it’s starting to reinforce that messaging right now. Now I know in my house, my kids will remind me if I step out the door. “Dad, don’t forget your mask.” They’re aware of this and they know this. And any time they’re near somebody, even outside of this, you can be approaching, their masks go up. So I think as parents, we have to start talking with our kids like we would anything. You know, kids starting a new school, you start right about now, getting them ready, checking in on their mental health is setting expectations for what the new year is gonna look like. And this school year is gonna look a lot different. So we don’t want our kids to walk in there on day one and be totally shocked. They need to know what’s coming and also what their roles and responsibilities are to keep themselves safe, but also to keep their friends safe and their classmates and their teachers safe. So I think the number one thing there is less about what you donate to your classroom, but the way I think you could support the classroom is to reinforce some of these basics to children repeatedly, so that when they actually go back to school, they’re aware of their role and responsibility. They take it seriously that this is a serious thing. And, you know, you’re going to have to wear your mask. It can be uncomfortable school be very different, we’re doing things a lot differently than we were. But that’s OK.

MODERATOR: Do you have any final thoughts for today?

JOSEPH ALLEN: No, I think we covered a lot. I guess I would just reiterate the comment on the context and the nuance are really quite important here, particularly in an emotional topic of schools. I have three kids, my own, I understand this. Teachers have the most important job in the world. And people are having to make decisions that they’ve never had to make before, including superintendents, about a really difficult topic. And, encourage, to any writing up reports about schools, to really take a broad, holistic look at risk and the terms of the costs of keeping kids out versus sending them back. A lot of the nuance here, because as we have seen in some of the problems that we distill these questions down into simple one off questions about any topic and lose the larger context, that’s where people get confused. It is a sticky, multi-dimensional problem, but it’s going to require us to report about it and talk about it. As scientists, with all of the complexity inherent it, if we oversimplify it, sometimes we get the headline that isn’t informative and actually hurts things.

This concludes the July 21st press conference.

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