 the round table that we have on the issue of pandemics. So I let Simon ignite the discussion. Very good. So thank you all for joining us. I want to introduce our panelists and there'll be some others who will, but in fact, let me just call on you and let you introduce yourself starting with Lona. Yes, hi, my name is Lone Simon. I'm a professor here at the University in Denmark. I've been in the U.S. for many years, but I'm here now. I worked on pandemics for 30 years and this year I spent my entire time working on COVID and advising the government and being on the press and everything. So I have nothing on my mind right now, so it's a good time. Jürgen. I'm delighted. I live in a strange country called Sweden, which seems to follow another route than other countries. I'm a professor of economics. I'm a mathematician by training and working on game theory, including evolutionary game theory, population dynamics and stuff like that. And now I've been working on modeling together with Simon and his lab of epidemiological models, including face masks and so on. I've also worked with the mathematician in France on optimal control of epidemics, waves, and things like that. So I'm an applied mathematician economist. You could call me a game theorist. Marino, who unfortunately... I'm sorry, I cannot join with the camera. It doesn't work and I don't know why it usually works. So I am now a professor and narrator at the College of the Polytechnic of Milano, Milano, Italy. I have been trained as an electronic engineer, but let me say as a mathematical model basically, then I started working in ecological modeling 40 years ago. I'm very much interested in disease ecology in the past, let's say, 15, 20 years. And okay, together with a group of other people, I have developed, I think, that the first spatial model for COVID-19 in Italy. So I'm very much interested in the round table. Josh. I'm Joshua White, Professor of Biological Sciences at Georgia Tech, where I usually work on virus micro-dynamics of, again, viruses of the small. We've also worked over many years on ecological modeling, epimodeling, going back to Ebola virus disease, doing some work in response there in this past year. I've been myself and my team critically involved in many aspects of COVID-19 modeling from estimating our nod and then going on to risk, as well as predictive models, forecasting models, and also with respect to Georgia Tech's implementation of a saliva-based testing program and essentially testing as mitigation. Delighted to be here. Mercedes. Hello, everybody. So I'm at the University of Chicago and I'm a theoretical ecologist working on infectious diseases, mostly population dynamics, the influence of climate, variability and change, environmental change, and also the interplay of evolution and ecology. Scott. I just took a mouthful of cereal because I've been on Zoom for the last three hours. So I'm at Columbia University. I'm an economist. I work on a variety of issues. I have worked on infectious diseases, mainly looking at disease eradication as a kind of extreme form of a situation which we rely on countries to cooperate to address the issue. The other end of that spectrum is when you have the emergence of a new disease. Those two are kind of at two ends of a long spectrum on infectious diseases, eradication and the emergence of a new disease. And obviously COVID is in that category. And one thing we're observing is that the international system is not responding in a very helpful way to COVID. We're entering a new era now with vaccine distribution, which I think is gonna be the most critical one for the international perspective. But that's the aspect that I'm more interested in. Thanks so much. Thank you. So Wilfrid Nadeefan will not be able to join us today. Unfortunately, he had a death in his family. I expect Ramanan Lakshman or Ion to join us. I don't see him yet. If you're there and I don't, it's just that I don't see you, Ramanan, please speak up. But otherwise I suspect he'll be joining us a little bit late. All right, there are many topics that we could address and we've only got 55 minutes to do it in. But I'd like to begin with something that's right at the core of dealing with COVID and that we're all interested in, which is the trade-offs between controlling the disease and making sure that we minimize the number in the hospital and the economic costs to society. And I don't wanna approach that from a theoretical point of view at the beginning. I wanna take a case study because there are a number of statements that are, there are a number of differences in the way governments have approached it. There's something called the Great Barrington Declaration that's been signed on by a number of libertarian economists and a few public health people. But the most striking difference is the Swedish policy, which differs, for example, from other Nordic countries and how they've approached, and most other countries as to how they've opposed the disease, appearing to rely to a large extent on the development of herd immunity by people getting sick. I oversimplify the strategy, but that's also been suggested or was suggested early on in the UK but was quickly reversed after an outcry. And I'd like to turn first to you, Jürgen, since it's the sweetest strategy and you're the sweet on the panel to tell us a little bit about the strategy and what you think about it. And then I'll ask Lona to go next since she does know Anders Teignal. You're muted, I think. We can't hear you at all. Okay, I'm sorry. So I'm not a specialist on Corona or viruses, but I have looked at this from a modeling viewpoint and also taking part in the debate in Sweden. The early, it was said by Anders Teignal and also other people that actually herd immunity was what they were thinking of. It was said that it is just as well to let it develop like that. We cannot do much about it and then try to mild on the consequences and protect the fragile and the old. They have later on denied that actually, but this has been documented. So journalists know about it and many in the public knows about it. So they changed what they said, but they did this. And then I would also like to connect to this. You said about libertarianism because it's very well known in economics that there is an idea of that the market will solve problems. Adam Smith, the invisible hand. If everybody thinks of him or herself and I sit in a rational and systematic way that will benefit everybody. It leads to a good state of society pariah to efficient allocation, we call it. Now it's also well known that that only holds on the extremely strong conditions which are so strong for many economists to say that it will not happen. And one of the conditions is that there is no externality as we call it. There's no effect of what I'm doing on anybody else. I'm only acting through the market. Now this is certainly not the case with an epidemic. So if I take measures to protect others or myself, that will have an effect on others. It might be that there's a cost for me to take some protective measures but I will use them too little if I would be thinking of myself only because I don't take into account then the external effect on others that I protect others by doing this thing. Now this is very well known and it's just embarrassment to hear the Swedish authorities talk and understand that in particular as if they haven't taken class, this class of basics, social science so that they kind of neglect. So they can say things like this, well, you can wear a face mask if you like and then at people then in Sweden, the attitude is that that is a sign of weakness. So I know of kids who have been ridiculed and scorned by other kids in school if they wear a face mask. They don't dare to do it because it's considered to be a sign of weakness or that you are not understanding the thing. So I think there is a very, very difficult situation in Sweden and one of the mistakes they have made is you cannot rely on individual decision in such a situation. It is a common problem. It's a public bad situation and it's a positive externality of measures that we take as individuals and therefore we have to encourage that and they don't. I think it's a major mistake. So let me, thank you. And then if I understand from the latest news when the Swedish strategy implemented initially there were a lot of deaths but many of them in nursing homes the numbers then went down but now they've shot up dramatically and there's a big debate as to what to do in Sweden. That's correct. Can I fill in with one little thing there that it was believed by Tegnell that since it was relatively widespread the disease in the spring it would not be necessary with measures in the fall because there would be some level of herd immunity. So they actually relaxed the conditions in the late summer and then it turned out he was wrong. So, Lona, could you give us the perspective from Denmark on what the Swedes are doing? Yeah, you're muted. Yeah, we can't hear a word you're saying. Hello, sorry about that. Yes, so our perspective is geographically we're sitting right on the other side of Sweden and we are very jealous. In Sweden they live three lives. They wear no masks, they get around they socialize in restaurants and we have had the lockdown so they're more typical of the rest of Europe and the United States. So let me say something because I will reveal that I'm actually think that and this is to the economist on this conference here that I think actually that Sweden came up with something that was sustainable a sustainable strategy which they brought in too late and then in the end they differed they deviated from it and that's why they're having a big problem now. But if you look in the middle space after they had a disastrous beginning they responded too late. They came in only in the end of March with some strong measures such as closing large gatherings and they'd be more careful about their elderly and then you see their curve of mortality swing around and they had a sustained epidemic control between May and September and this might be the most misunderstood fact in the history of this pandemic but this is the truth. So my point is that if they had introduced that strategy earlier at the time we in Denmark shut down our whole country we would have had a sustainable epidemic situation there and they would have avoided all their deaths in the other sector and so in effect they're really showing us the way to if the vaccines didn't work maybe the Swedes are onto something here and I am missing that debate and that angle here. I wanna say that in the end of the day they ended up just like you said Joanne they actually said okay it's going very well they were the poster child of Europe then with the lowest infection rate in Europe and despite all their openness and they said fine let's open up the big conference the big meetings and they went from 50 up to 300 and what happens fall happened and schools happened and this happened and all of a sudden they're in a major bad situation right now but I don't think that has anything to do with the strategy that brought them safely through the from March from May to September. So I'm ready to stand up for Anna's signal I think they were lucky but they definitely onto something. So Lona you were one of those who wrote in opposition to the Great Barrington Declaration. What's the difference between the Swedish strategy and the Great Barrington recommendation? The Great Barrington Declaration is all about we should just put the old people in a closet on a basement somewhere and then the rest of us ripped through this epidemic it's nothing severe. I have so many reasons for objecting to that that's not even funny. And if you notice the people who signed that declaration that they are not the infectious disease epidemiologists that you usually seen this field they all signed something called the John Snow Memorandum and I'm not a fan of signing things like that but I actually signed this one because I think it's a pretty important discussion to have and to show that we were many people who thought differently about it. I don't think this has anything to do with Sweden by the way. Okay. Josh you've thought a lot about these sorts of issues and various strategies. Maybe you can weigh in on this. Yes, I'll say a couple of comments that we are talking about dichotomies and I think one of the things that's been problematic from the beginning is the option of dichotomies. And I think there's been a false dichotomist thinking from the outset. When all you have is a lockdown maybe the only alternative is open it all up but why are those the only two options at play? And so one of the things if we go back to the sort of initial, the Swedish case I mean, if you look at the daily mortality compared to Denmark or to Norway or to Finland and we're talking 10 depending on which country 10 in some cases more fold higher. So obviously there's something that went very wrong there especially with vulnerable people but still had these were people's parents and grandparents and loved ones and so on. Where we've tried to make an impact is to try to both inform and also address alternative strategies. And the one that we've tried to work on both in theory but in practice is testing as a form of mitigation. And particularly now one of the big worries I have is that we're entering this vaccine phase where I think there's a sense well, good thing is on the way and it is it's incredibly good. But we are also a period of the United States where there's tremendous amount of spread there's been our resurgence we're getting 3,000 fatalities a day at this point in the United States a day. And that doesn't seem like it will stop soon in part because of Thanksgiving and meetings there but also because we haven't invested in universal mass wearing and as virus testing as a form of mitigation. At Tech we ended up like UIUC like many other places making this investment. If that needs to then transition to the next level which is state and national level using a part of an intervention policy and I'll just have one last comment there which is there's this sort of crazy Trumpian comment about we have so many cases because we test so much but I wanna flip that around and basically say that in the near term more testing will lead to more documented cases but fewer actual cases in the long term. And we've seen in practice here at Tech the identification early of outbreaks means that we can actually stop change of transmission before they start. And so when I hear this sort of options I'd like us to on this panel at least open the idea there are more options. It's not locked down or open all up. There's lots of ways to be more targeted in productive sense so hope we get to some of that. Okay, others I don't wanna put anybody on the spot because I called on the people that I know have been working on these things but Marino, Mercedes, Scott, I wonder if any of you have any thoughts that you'd like to share on this? Yes. Let's see, Ramanan's joined us now too, you know. Hi, Joey, I used your link, Simon. I wasn't able to make it work with mine. Just to let Ramanan know what we're discussing we're talking about herd immunity strategies, the Swedish strategy, the Great Barrington Declaration and the trade-offs in general between minimizing the number of cases and possible damage to the economy. So, go ahead, Scott, were you about to? Well, can I have a word, Simon? No, Marino, okay, I'm sorry, yes, go ahead. No, well, you know, there are different containment measures that you can implement and I'm not an economist but according to my idea, they have different costs. So, for instance, wearing a mask or, you know, protection is very inexpensive. And let me say, because Italy was the first-hit country in Europe, that it is incredible that, you know, that this very simple containment measure were not implemented from the very beginning. They're very expensive and Europe had one month's time to prepare, to get ready because, you know, the first documented case in Italy was the end of February, you know, 21 February and we already know, we had already an idea of what was going on in China and therefore we had one month and, you know, masks are really inexpensive and, okay. Okay, now, of course, if you stop traveling, that's much more costly. So, my idea that really Europe was missing an opportunity and so we have to go into lockdown now again and Italy is now in lockdown, especially my region, normally where I'm even in a lot of conditions. And that is due to the fact that people, you know, were communicated the wrong message that everything was over, that the sheer truth. And according to me, the different option have really very, very, very different costs. And they, you know, and well, we conducted a study of that. So, you know, reducing mobility cannot, can never bring R naught below one. Reducing transmission rates, it can. Isolation and testing is more costly, of course, than wearing an inexpensive mask, an expensive face cover. And it is more effective. If you can isolate people, identify an isolate, that's my idea. Can I make a few? Yeah, go ahead, Bruce, please. So, yes, some very rapid comments. One of the, I think, behind perhaps some of the people who signed that declaration and do some modeling of disease, there is an interesting issue that I think has to be resolved is that, you know, we have a poor sense of the levels of herd immunity that must be reached. And part of the problem there is with the estimates of how the heterogeneity and susceptibility modifies R zero. And I think there was very interesting work by Gabriela Gomez and her kinds of models in epidemiology, they are worth looking at. I think it's a beginning in that direction, but it is a problem. How do we deal with that heterogeneity and what does it mean for the level of herd immunity? And I think that that may have perhaps misled some people to think that that level was lower. I don't know, because I think there is tremendous uncertainty on that number. Second comment, Lone mentioned the May to September reduction. I think a big elephant in the room for COVID is the role of seasonality and the role of climate factors through many, many routes, not just direct effects on the virus, but also on behavior. And there is a paper by Javier Rodo and while I'm in it, but mainly by them showing clear effects of seasonal climate, which by the way, previous modeling said should not have an effect given the very large number of susceptibles. That is not the picture. And I think the mean field models are sending us in the wrong direction. Marino mentioned travel. And my last comment is that I think they have handled travel at the very interesting scale, the large scale, right of travel between cities. There is a question of movement at the micro scales. And I think that is a much more difficult issue. Good. Scott. Could I just, sorry, Sam, a very brief comment to Mercedes, first point, if I just may say that, one thing. Yes, sir. You talked about the heterogeneity. And that is, I think, also super important. And I just want to alert you that there is a science article, recent one, by Tom Britton, Swedish mathematical biologist published in Science. I have seen the paper. Yes, Tom Britton published this. The paper by Gabriella Gomez had been out in the archives for a while and she has been modeling these kinds of things. So, yes, they are in the same direction and I think people should look at it. I would recommend young people here who are interested in doing work modeling. This is one aspect I think would need a lot of more work. I agree. Scott. Yeah, thanks so much. Great comments from everyone. So I want to go back to Jorgen Weibull's introduction. I think it's really important for epidemiologists to understand and integrate human behavior into their models. And basically where he was starting off was this what we would call a kind of a competitive equilibrium when people are acting individually. Basically, they're going to be inclined more or less when you bring richness of human behavior into account, it gets a little complicated. But they're going to be ignoring a big part of the effect of their own choices and actions on others. So the result of all that is that you would expect in any society that there would be too little social protection. And that's completely to be expected. And that's why we have public health policies. And that's why there's a conflict inherent in this situation between the public and the private. And I think that's really important to understand because when, if people are asked to take measures, we need to understand that there's a reason why they wouldn't do that on their own. And what I would say about the policies we've adopted is they haven't always understood the motivations that are coming from individuals. Now, this gets super complicated because we have a lot of very bizarre things going on with human behavior. I think we're gonna get to probably later in the session about social norms, but also about beliefs and so on. I hope we get to that later. But even leaving that out, what you actually need, if you really wanna change that outcome is you need to change the incentives people are facing. And one thing I've noticed is there's been a disconnect between a lot of the economic policies that have been adopted. And this goes back to your original question, Simon, about how to trade off control of the pandemic with maintenance of economic function. For example, asking people to stay home while at the same time not compensating them for a loss of income from work. There are interventions that you can take from the point of view of public policy that would reinforce the public health policy. So these two things have to be synchronized. And where we've seen a lot of problems is because there has not been this synchronization. They've been out of step. And then there's this tension and people are upset and they're pointing fingers and they're fabricating all sorts of myths as well. But what I'm trying to get to is that that tension is to be expected. And that's why those policies need to be integrated. I could also add in dynamic sense, I think this also, we should not be surprised that there would be waves and that public policy could even enhance or amplify the waves. Thank you. Before I go on to the other panelists, I just wanna say that Scott implied correctly that I had a list of about 10 questions I was gonna address. We'll be lucky to get through two today, but that's okay because I think that this particular issue lays bare a lot of questions and things I talked about on Monday in my lecture, which was the importance of looking at things like social norms and public goods problems. And if we get no further than talking about those things today and why the theoretical ecologists ought to be thinking about those things, I think we will have done. Ramanan, why don't I go on to you and then back to Josh and Lona. Yeah, sorry to join late. So I don't know if some of this has already been discussed, but just for back in March or April, one of India's biologists, lead biologists, and I wrote a piece in Indian Pediatrics, which is the main journal for the Pediatric Association, saying that in the absence of the ability to really control the epidemic in India, which we thought was difficult given the density of population, that a gradual acquisition of herd immunity was not a desirable outcome. I mean, it was not meant to be an intended strategy, but it would be an unintended consequence of the way things were going. And by the time December rolled around, that transmission would have slowed down significantly because there would be pockets where there was significant amount of exposure already. Now, India has been through some severe lockdowns, but this seems to have come to pass, which is that the positivity rates are now quite low. It hasn't, India has not seen the large number of cases or the deaths in recent months compared to earlier in the epidemic. And age structure of population also makes a difference. So I think that what works in one country might not work in all countries because of, again, age structure, which is if you have a lot of young people, and just for comparison, in India, there are about 6.5% of the population is above the age of 65. I believe that proportion for China is about 10 or 11%. That number for the UK is about 18%, and that number for Italy is about 22%. So I think these discussions have to be tailored to what that age structure of the population really is. If you have a lot of young people who get the disease but sort of act as a buffer against the older folks getting it, which seems to have happened in many places in India, perhaps you don't see the kind of rapid number of deaths of the elderly population that you've seen in other places. That said, there are still other issues, which are that in sort of one large COVID epidemiology study that we'd published a couple, actually last month, interestingly, mortality rates are actually quite high in the age group from 40 to 70 in India, compared to most other countries where that mortality rate is actually highest in the 85 plus population for the most part. Now you have some sort of a selection effect where people who have reached the age of 85, essentially because they made it there, they probably have fewer comorbidities. They didn't die earlier. So they kind of talk with them the ones compared to sort of in other countries. So compared to other countries, compared to China, Italy, Brazil, the US, India's above 85 mortality rate is actually the lowest, in fact, but it's highest in the 40 to 70 age group, probably because of undetected hypertension and diabetes, which are major risk factors. And in fact, all the COVID is an infection disease, this comorbidity, driving mortality is such an important effect. And I think, again, the answer to whether you'd go with, acquisition of herd immunity, or you try to shut down to make things happen, again, depends on the proportion of the population that is diabetic or hypertensive. In our study, we looked at about 5,700 deaths. I think about 64% had at least one comorbidity and something like 35% if I remember right, had two comorbidities. So the comorbidity stuff is really quite important. And I think that an age structure together will really be guiding principles for whether, what sort of strategy one might want to adopt. I don't think there's sort of a universal idea here, which in all conditions, you would do one or the other. Josh, you had your hand up and this is a very natural segue into things like in terms of shale populations that you've contributed a lot about. So I know you have thoughts on that and that probably wasn't why you raised your hand before, but go ahead with whatever you want. Okay, I'll try to make a bridge, which is that I think one of the challenges you're talking about, whether it's Great Barrington or even just how to interpret peaks has been one of the most challenging things in this whole epidemic. The timing of those may differ, but the temptation to assign or ascribe the mechanism of reaching a herd immunity threshold in these early peaks, I think has been deeply problematic. And Mercedes, I'm aware of that heterogeneity work. I think it's very good. We've also worked on some heterogeneity issues, but the thing going back to Scott's comment about behavior is that it's clear that the herd immunity threshold depends not just on the fraction of individuals who may be immunologically naive, but also on the behavior of individuals. I think people have misconflated those ideas. We've shown in a paper that just came out that you can be aware of transmission, change behavior as a result of transmission and get a peak that goes away and then come back as our awareness fades, and especially if there's fatigue. So you can get more than one peak having nothing to do with crossing this herd immunity threshold. And I think that's been a big mistake for people to misinterpret. And heterogeneity, yes, it can be there, but we can also look at places like fishing boats, and that's a case where it's very hard to isolate, as you all know, and see 85% plus attack rates in a short period of time. So if we start to act as if we're on fishing boats, meaning going out and interacting in large groups, then it's going to be the case that we're gonna see increases. And I don't have to go to the fishing boat. I can look at Greek houses here in the United States, including some on this campus, in which maybe not through fault of their own, but just the introduction of a case in dense living situations. And so I frame that only in the sense that I think that this notion of heterogeneity can exist, but also not necessarily be explanatory, vis-a-vis peaks. And the last thing I'll just, yeah. And then I'll wait, the shield immunity can be a different time. So. Well, I'm happy to have you talk about the shield immunity, Josh. I just want to point out for this broad audience that when Josh talks about Greek houses, he means fraternity houses. Yes, sorry, that's right. Fraternity, all right. We call them Greek houses, fraternity and sorority. So we call them Greek houses, but dense lived, learned environments on a campus. Sorry about that, yes. Yeah, so Josh, do comment on the shield immunity. I'll just make a brief comment, because I see Mercedes is only wanting to say, so very, very, very briefly, only that from the outset, we have hoped that testing, both for a virus and for antibodies could be incorporated as part of response strategies. And the virus testing, I think is obvious, but the antibody testing we viewed as very important in so far as there was a lot of evidence that this was not going to be a seasonal beta coronavirus issue, that there was going to be protection that we can't know how far out, but many months at least, if not longer, and that individuals who might be seropositive might be able to take on additional roles, particularly in protecting those who might be vulnerable. And I think, again, we've missed multiple opportunities to go from imperfect but actual information and avoid it for some reason to take action on with another cost, which is not leveraging that test information to act differently, to try to get more targeted. And in lieu of targeted responses, we're stuck with lockdowns, which we know have caused. So that's a brief summary. Lona. I have a comment there. We have had so many exciting things just thrown on the table and there's no time. To Scott, I think you'll be happy to know in Denmark we actually have surveillance system of people's behavior. And this goes into the models that actually are used to figure out what's going to happen in the future and the forecast and all of this. So it's available in the public domain if you want to see us as well. In Mercedes, about the herd immunity, we have observed this. We've seen herd immunity in the Northern Amazonas, in the town there. We've seen it in the Bergamo, Italy, for those of you who are in Italy, and we've seen it in the Mumbai three slum areas where it seems to peak at 60% seropositives. It seems to be something around there and probably this heterogeneity we have with this disease will mean that it's definitely not gonna be higher than that. And I also want to say that one thing that's really important for us to mention in this conversation is that this, we looked at pandemics of influenza for a long time now. I looked myself for a hundred years of worth of them. And this year is a totally different beast because it has this over dispersion, this heterogeneity in the spread. And together with colleagues at the Nears Boys Institute, we actually have used an agent-based model to incorporate this fact that only 10% of people spread most of the disease going forward. And we just so excited to, that we think that actually the solution lies in controlling the context in the public space. And there's way to do that without really being able to pinpoint who is the super spreader. You can actually come the closest down. So for me, that's the one really exciting thing that has happened during this whole pandemic is that understanding that flu is one thing. It's like a freight train. You can't stop it. But this one, you have a little button you can dial up and down if you can afford it. That has everything to do with this over dispersion heterogeneity phenomenon. I just thought I would say that. First savings. Yes, so I agree, Josh, you brought a very important issue. I didn't mean to say by herd immunity to turn around of the pigs. In fact, it's a complete misconception that the turnaround of these pigs, of these first pigs had to do with herd immunity. I just meant herd immunity estimated from these susceptibility models is lower than in other estimates. Now, in response to what determines the pigs, of course, there is a very an interaction between herd immunity and possibly seasonality due to policies and climate. And I think we see this of course in diseases that you can say are SIR and very different from COVID because we know they are seasonally driven, something like dengue where you get emergent serotypes lasting two or three pigs. And I think what determines the pigs is a very interesting interaction between the transmission dynamics and the timing of the changes in transmission due to seasonality. And I think whether that seasonality comes through behavior and through myriad factors that influence the virus, we will find that it plays a role here and how it interacts with policy and makes for a very confusing, unfortunately, a very difficult inferential aspect of this disease. Marino. Well, I know a comment on heterogeneity. I don't know what you're meaning exactly by heterogeneity, we'll say that, but we included heterogeneities in our first effort in Italy because the model that we conceived was actually space explicit. So we included 107 provinces in Italy and looking at the spread of the disease in Italy, it started in the north and then it went to the south. And then when the crisis was considered over and people were allowed to go to the seaside, the city of Sardinia and Sicily, it spread to the Sardinia system. Now, you can actually calculate an R naught, which includes the geographical, at least the mobility, let's say. Then of course, there are other heterogeneities, heterogeneity of behavior, different age classes, behavior in a different way, susceptibility in the different age classes and the different, say, working environment is different and so on and so on. But after all, for all the studies around the world, R naught, without any intervention, is about three. Let me say that, that might be 3.5, might be 2.7, but anyway, everywhere, of course, it might be differently. So talking about herd immunity to me is ridiculous, let me say, because with an R naught, which is about 3.5, 2.7, whatever you want, herd immunity is rich, where about two-thirds of the population is being infected. Now, two-thirds of the population being infected means a lot of death, an incredible, an incredible amount. Okay, so we had a result of several seroprevalence studies. So in Italy, around July 15, there was a sort of sample all over Italy and the seroprevalence in Lombardy, which was my region, 7.5%, that's the highest in Italy, other region were 2.5%. So it means that before reaching herd immunity, of course, there are some specific locations. So if you go, for instance, to Bergamo in a valley, they have 40% people being infected, okay? The second thing is that we already know that you can be reinfected, that this talking about, okay, I will cite you one case, for instance, that there was a seminar by Antonella Viola a few days ago, and they have seen in Padua, one guy who get infected, recover, then he was reinfected again and died. So it is somehow clear that immunity, immunity might last just a few months. So these idea of reaching the herd immunity, let me see, I don't know, it doesn't, I don't know. I'd like to, let's let Lona, cause that's a controversial point about whether the individuals actually recovered. So Lona, could you're to close? Yeah, I'm aware of this having occurred, even one got more sick the second time than the other, but I think we can know for sure now that this is not very common. We see that, for example, in Bergamo, Italy right now, which had this terrific herd immunity in the first wave, it is faring very well in the second wave, opposite other towns in northern Italy, which I have had a very bad second wave. So that's just one of many lines of evidence that I think that's not gonna be an important one. Antibodies are okay. Even in Iceland, you can now travel in with an antibody passport. On this issue of super spreaders, by the way, you may have seen that this one biogen meeting in Boston apparently was accounted for about 300,000 cases. So I'd like to call Daniel Fisher. I don't know Daniel whether you can unmute yourself. Okay, go ahead. Yes, I can unmute. So I'm a theoretical physicist at Stanford and my only direct relevance for this having worked a little bit on spatial spread by a long distance motion in abstract models. I wanted to actually ask a question about homogeneity, not about the heterogeneity. So in the spring, if I looked at New York City and you looked at all of the high density parts going all the way out to the rich low density suburbs, the variations in the number of cases were not all that high. Then there were factors of two or maybe three in some case, but not enormous. If you look in LA in the spring, they're again going from the higher density poorer areas to the low density richer ones. There was also not all that much variability, but the whole area was much lower than New York. And I wonder if there are any thoughts as to what the explanations are of some of that. I think Josh made the comment that clearly in most places, at least, the number of the lost susceptibles was not playing a role and certainly not in those, I think in LA area there. But then what is it that can give rise to that level of homogeneity within regions? Did anybody want to respond to that? Hello? So Lehan, yes. Yeah, I'm also a theoretical physicist and actually me and my students started to, you know, work on some models since February because things started in China and we were really wondering what's happening and whether things we can do, make some models or inform the policy makers and so on. But answering Daniel's question, I mean, these early models, we just took the standard approach from epidemiological community and we'll mix and so on. And now people of course thinking about heterogeneity, but I think that probably is not really the most crucial issue. I think what Daniel asked, because after initially this growth, exponential growth, there's some variability, maybe R zero different places, somewhat different. But after some time, then you always see that kind of level off at some value. And I think Daniel is asking which value, right? So it really has to do, I think the human factor is very important that people get scared and they take more precautions, whatever community they belong to. So that kind of bring down the growth and eventually you'll reach like R zero equal to one or something. If you start to see the decline, sometimes you have to overshoot a little bit, but then some kind of declining. But once people see this declining, then they kind of tend to relax. But doing this this first way, people still, they are very cautious. They don't immediately relax. And that's what we see in Hong Kong. We actually now in the fourth wave. So I think this, the overall level is really has to do with the local community. How they are like worried, they, how much precaution they take themselves in addition to what the government is doing. So I think this kind of a self-imposed kind of behavior changes that could at some point will bring down because everyone now watching the news, right? So maybe they are seeing the increase or decrease more than the absolute value and they kind of respond to the growth and not maybe instead of the absolute value. And so if the local community, they are, you know, take this kind of precaution earlier, then it will stop, it will level off at the lower level. So that's my kind of interpretation. I mean, I agree. I mean, I think the only reasonable interpretation is that there are, you know, rather long range behavioral changes. You respond most of the things right nearby. You respond somewhat to the things applied of the city because of some amount of mixing in the city, but not enough to give you like a well-mixed situation. And then you respond less to things in the whole country and, you know, less even to the whole world. So I think it is something that's, you know, it's surprising that that gets you to some of these levels of homogeneity that there are. But I, yeah, I think those things naturally give rise to sort of can give rise to dynamical, to waves and things. Daniel, very quick comment. First of all, in Georgia, we saw imprints of heterogeneity that lasted a while. For example, in Albany, Georgia Southwest, there was a funeral that sparked an outbreak and that led to an imprint locally in that county and adjoining counties for quite some time that we would not have expected if we just assumed homogeneity. In New York City, there's strong relationships between socioeconomic levels and incidents. And in particular, with the number of residents for household, Jeff Shaman, Mikhaila Martinez, and a few others have done these sorts of studies. So you see those factors. There's also relationship to ability not to take the subway. So there may have been, you know, some gaps between awareness at the outset, but there are definitely, you know, let's say links between socioeconomic factors, mobility, crowding and incidents. So I'm just trying to add those layers into your comment about homogeneity. Yeah, absolutely. I mean, those all would give rise to a lot of heterogeneities. And, you know, with changes in exponential growth rate, you expect all those things to be amplified. And so that has to be rather a big effect that sort of suppresses them to get the sort of lack of heterogeneities on some of the scales. But yeah, anyway, that's enough on this point. Well, let me turn to Ramanan now and then to Jurgen. Yeah, thanks, Simon. So, you know, I teach a class in Princeton where the main theme really is around this whole idea of people responding with behavior to prevalence. And, you know, there are lots of examples, of course, from HIV, which is in some sense a slightly more stable disease because people get to observe it and then, you know, get to respond to it in terms of their risk-taking behavior. I am not sure if that is really panned out in the case of COVID for a couple of reasons. One is adapting to the prevalence out there requires having fairly good information about how bad things are out there. And I don't think the level of testing has been nearly enough in most countries to be able to support that kind of data. We know from zero-prone studies that, you know, at least in some countries, we're picking up one out of every 20 cases or one out of every 30 cases. So we don't really have a good handle. And when I say we, even people who are studying this, don't really have a good handle, let alone individuals. Individuals are responding to waves of panic on the media, you know, how many shows they watch, which are not necessarily correlated with, you know, what the true nature of spread is because there's been spreading lots of places where the testing has been wholly inadequate and therefore it isn't as if they're responding to something which is very rational. That's the first point. The second is that just because it's a new disease, I think people have found it quite difficult, at least for the first six months, to accurately calibrate their risk or risk-taking behavior to the disease in a way that actually makes sense. What do I mean by that? It really means that for HIV, you knew it was actually transmitted. So if you didn't have needle exchanges or you didn't have, you know, blood transfusion or you weren't having unsafe sex, you were pretty safe. Here, people weren't clear whether to pick up the newspaper. They weren't clear whether to go play tennis or, you know, to go out of the park. So given that there was so much confusion about what risky behavior constituted and what was safe behavior, I'm not entirely convinced that for that long period, probably from March through to August or September, that people had any clue what they were doing or, you know, or if even governments had a clue about things that were actually problematic versus non-problematic. And I think, you know, some places get bars open but shut down schools, you know, some places shut down schools and, you know, sorry, get schools open but shut down the bars. I think there's a lot of confusion out there. And this sort of, you know, stable understanding of what's driving these peaks up and then driving them down. I think it's a result of a lot of confused behavior rather than really of what I would call rational behavior because it's all with fairly incomplete information. Very good. Jorgen, you had your hand up, I think. Can't hear anything from you, Jorgen. I'm muted. Yeah. Sorry, thank you. Yes, no, I wanted to follow up on this with behavior that Scott was taking up some little remarks that, you know, from an economic theory viewpoint, you think of individuals as being fully rational and selfish and they take in any information they can and they can treat information in a good statistical way. So they can make inference about things that they see around them. And we know, of course, that that is a very formal of real-life human beings in many dimensions. One is the belief formation and there can be these panicky situations and things like that, but also the motivational part, I would say. So the strict egotistic, you know, motivation, which is a classical economics, motor of behavior is not true, you know. And one situation when it's not true is when you have a public good situation in a small community of people who meet regularly over long times and so on. So we like in the village and the family, people do care for each other in another way then. And that can be explained by game theory and so on. So that's one thing. Another thing which is very important, which has been added now in economics to economic incentives or social incentives, social norms, that we are social animals and we care about what others think about us and our behavior. And that's very clear. And I think that this is not what has, this has not been used by some policy authorities. One could use this. I mean, when I think of smoking, the anti-smoking campaign was very successful, but because you can see and smell the smoke in a restaurant and people don't smoke. You don't need to have a policeman in a restaurant. People will frown upon those who go in there and smoke. You don't see the corona that I'm spreading perhaps when I go into a shop. But I'm now in Norway and in Norway, if you don't wear a mask, when you face mask, when you go in, people will frown upon you or even ask you to go out and so on. While in Sweden they don't. So I think there is a social norm, but it could be used in a positive way that we have something common to think about and care for. Also to those who are not very close to us. And that is something I think is up to political leaders and or agencies to inspire that. And we also know from experiments that individuals, they are not purely selfish, not surprisingly. So there is a tendency in most humans to have some moral component that we would like to do things that we think are the good and right things. We have some tendency, not to very strong, is heterogeneity again. But if I inspire these things, one can get much beyond what we have now. And this is something which I think we need to incorporate into the classical SIR models and so on, the population models in epidemiology, which are rather mechanical on the behavioral side. So I think we could combine here many fields and combine behavioral understanding and economics and game theory and these dynamics. And that will give a richer model and possibly better ways to try to influence the control and epidemic, for example. Thank you. Very good. Marino. Okay. Well, you know, a comment. I think that, you know, what has been working, clearly heterogeneity is important and heterogeneity in social behavior is important and you see the difference. So for instance, take Japan and they had a very low number of people who died and they didn't go into a real lockdown like Italy. But lockdown in Italy worked. And then, you know, then they released a lockdown and then after a while, we started again with the second COVID wave. And now they went into lockdown again later than what, I mean, I would have implemented lockdown earlier given what was going on in Italy. And now the numbers are going down again. So clearly the containment measures are working. And well, you know, the homogeneity you see now is clearly due to the spatial diffusion of the disease. So the spatial signature is clear with the COVID starting in China that spreading the rest of the world with the male lead through air travels and then going to countries and then, for instance, reaching Italy. And of course, the Fossa in Italy were in the northern part of Italy because it did the mostly industrialized part of Italy with a lot of the connection with the rest of the world. And then it went south when the tourism season started and so on and so on. Seasonality, well, it is clear that COVID is spread mainly when you are inside a closed environment. So clearly during summer, the contacts are not so close. And in fact, there is an interesting remark that it went up in summer in Texas and Arizona because people want air conditioning. So they stay inside and the most of the contacts are inside a closed environment. And it is very clear now that the main way that the disease is spread is the respiratory and closed contacts and the aerosol and the droplets. So clearly seasonality is related to the effect and also it's related to comorbidities because clearly during winter respiratory disease and ailments are more common. So old people might suffer from comorbidities, especially during winter. But I would say that lockdowns were the most effective way of limiting the disease. That's my opinion. Thank you. One last quick comment. And then we have to tie things up. Right. So just very quickly, just to kind of echo, build on what Jorgen said, I agree with everything. Social norms can go in the two directions, of course. So there's a social norm to wear a mask. There's a social norm not to wear a mask. And we're seeing both of those things. There's another aspect to this though that I think is really important. And that is where people get their beliefs. And there's very strong evidence that beliefs, there's not only the normal variation, but that there's a correlation with people's ideological identities. You see it very strongly in the United States, but I think it's also in the UK and other places. And this is really, I think a real problem for us because of the political connections and also through social media. Basically, I think it's a very strong evidence that basically introduces the ability of others to manipulate beliefs. And I feel like this is something that's happening on a pretty massive scale and it's making the normal kind of public health policies really difficult to implement. So we have the other problems mentioned before, Ramana mentioned that we don't get to observe prevalence. We also, people who are transmitting without symptoms, there are all sorts of other complexities that are already there. We have all the normal richness of human behavior, but on top of that, we've got this very disturbing heterogeneity in populations in terms of their beliefs and where those beliefs are also being manipulated by others for political and other purposes. Thank you. So this has been an incredibly rich discussion. We got almost through the first question I had laid out. I hope that, first of all, I wanna thank all the panelists and the others who chimed in. I hope this has convinced people of what I was arguing in my lecture on Monday, which is if we're gonna go forward to solve not just problems of this sort having to do with pandemics, but also climate change and other issues, we've got to have more sophisticated incorporation of economics and social factors in human behaviors, looking at things like social norms, prosociality, political polarization, as Scott was just mentioning, et cetera. So we could have gone on for three hours on this, but it's been a great discussion and thanks very much. We've got another panel discussion tomorrow on economics more generally. So anybody, anybody of the panelists who wanna chime in and listen to that, I'm sure, just drop us a note and we'll make sure that I think the same link will work though that you used today. Mateo or Jacopo, Jacopo, what time is that panel tomorrow? So it's half past two. It's half past two. European time, so that's, I guess what, 8.30 in the East Coast of the United States. Yes, yes. Okay, very good. Thank you all very much. Great discussion. Okay, thank you very much. The school resumes tomorrow at 12. So have a nice evening or day or whatever. Thank you. Thank you. Happy memory. Thank you. Thanks, Simon. Bye. Happy new year.