Coronavirus (COVID-19): Press Conference with Marc Lipsitch, 10/19/20

You’re listening to a press conference from the Harvard T.H. Chan School of Public Health with Marc Lipsitch, professor of epidemiology and director of the Center for Communicable Disease Dynamics. This call was recorded at 11:30 a.m. Eastern Time on Monday, October 19th.


MARC LIPSITCH: Thank you all for being here. I’m happy to talk about whatever is on people’s minds. As everyone’s aware, last week, one of the big stories was the Great Barrington Declaration and the response to John Snow declaration that a group of us signed in response to that. I’ll tell you a little bit about my perspective on that whole discussion, because I think it’s important as background. Especially watching the president’s rally yesterday, where he called on people to just get back to normal life and resume their contacts as before the pandemic, which is consistent with the strategy that he’s been pushing for a while, but also that was outlined in this declaration that took the name of a very beautiful town in western Massachusetts.

The four of us, Carlos Del Rio, Rochelle Walensky, Gregg Gonsalves and I, wrote a piece in The Washington Post last week that laid out essentially what we think about the situation at present. The situation is that most of the population in this country and indeed most of the world remain susceptible to this virus. Increased contacts will mean more transmission. The Great Barrington declaration suggested that we need to make special efforts to protect the most vulnerable among us, which I think is an uncontroversial and obviously correct statement. But the question is, do we believe that those efforts by themselves would be sufficient to \reduce the toll on the health care system and the toll on people’s lives? And it’s my view and that of my coauthors of the op ed and of the John Snow memo that there just is no evidence whatsoever that we know how to effectively protect the most vulnerable. Partly, we don’t know how to identify all of those people. Some of them we do. Some of them we can guess based on their age or their comorbidities. But there are people who have very severe disease who are not in pre-identified groups. For example, over forty thousand Americans under 65 have died of COVID-19. And that’s a small proportion of the total. But it is a very large, absolute number. So we don’t know how to identify them. And more importantly, we just don’t have, at the moment, a way to protect one segment of society from another segment of society that’s spreading the virus.

So it’s an aspiration I think many people share that we would like our lives to get better, back to normal. The question is whether it can be done safely and whether there’s some way to protect those who are at greatest risk while doing so. I think the answer is very clearly, unfortunately, no, until we have a vaccine that is widely available and widely used and highly effective. So that’s the brief thing to say about the Great Barrington and herd immunity discussion. I think what really is on everyone’s mind, who is trying to do good work at this point is how are we going to, if we’re not going to just return to normal as I think we won’t in many parts of the country and many parts of the world, how do we make that as bearable as possible? And how do we minimize the most dangerous transmission settings and maximize people’s ability to have some form of social interaction, including school interaction and others? And I think that’s what much of the epidemiologic effort should be going towards right now. I think it’s a further aspect of the failure of our government to mount a comprehensive response to this pandemic that the data don’t really exist to support very robust efforts to find ways to engage in safe activity. We have broad concepts like avoiding crowded indoor spaces with poor ventilation. But the detailed epidemiological studies that should have been done are among the many casualties of our national response, in my opinion. So, we’ll leave it there and take questions.

MODERATOR: All right, first question.

Q: Good morning. Thank you for doing this, Dr. Lipsitch. I don’t know if you’re aware of the new report out this morning from the American Health Care Association. Their latest data shows new infections in nursing homes began rising in late September. So it’s ticking up. My question is, following on your opening remarks, as community spread increases and the number of daily new infections rise throughout the country and given the precautions that are in place or are not in place, what do you expect will happen in nursing homes in the coming weeks and months?

MARC LIPSITCH: I think we can only expect increasing introductions into nursing homes and increasing numbers of outbreaks. I mean, testing is now instead of being nonexistent almost as it was before, it’s now simply inadequate. Which is an improvement and will potentially help. But I think we can only expect that in places where we have a lot of vulnerable people and a lot of necessary human to human contact, there will be continued outbreaks and probably more as community transmission increases. You can think of sort of, well, it’s similar to in schools. If community transmission is low, then the chance of having an introduction into the institutions, schools or nursing homes is small, if it’s more widespread than there are more people to introduce it. And one introduction might by chance not lead to an outbreak, but many introductions are more likely to. So I think we can only expect increases and we need to deploy the resources we have of testing and staffing nursing homes appropriately, etc., to do our best. But I would expect more.

Q: Quick follow up if you don’t mind circling back to the logic that’s circulating in the White House that you referred to earlier, suggesting that we can protect the most vulnerable with the goal of achieving natural herd immunity. What does the uptick, now, in nursing homes say to that logic?

 MARC LIPSITCH: Well, it’s the exact opposite. If we were effectively protecting the vulnerable, then the community transmission would be accompanied by no change or even a decline in nursing home risks. But this is exactly what people have been saying. And again, all of us would like to find ways to better protect the vulnerable. And many of us, my colleagues, Michael Mina and Caroline Buckee, have been working on approaches to better use staffing patterns in nursing homes and improve staffing patterns in nursing homes to reduce transmission risk. We don’t like to do that, and some proponents of the focus protection ideas, which is a nicer name for the herd immunity notion, some people have said, well, of course, we should spend more resources on the most vulnerable than on the least vulnerable. Nobody would argue with that. Of course, we should. And that’s what many of us are doing. The question is whether you do the whole of society approach with extra resources for the most vulnerable or if you do only the most vulnerable and the letter doesn’t work.

Q: Thank you very much.

MODERATOR: Next question.

Q: Thank you, Nicole, and congratulations, Marc, although I think that might mean you’re getting old.

MARC LIPSITCH: That part is unavoidable.

Q: It’s true. Better than the alternative. So I wonder if I could get your quick take on what’s happening in Massachusetts. Is it looking like we’re going to be following Europe? What’s your understanding of what’s driving the spread here as it ticks up and up? And in particular, is there any data or any type of data that would help us understand better what’s driving the spread? Thank you.

MARC LIPSITCH: I think that Massachusetts is in certainly better shape than many parts of Europe. And then many other states. And that’s because of a very relatively cautious approach to reopening and aggressive efforts to contact trace and otherwise reduce transmission and send testing facilities to hotspots and the like. So I think that it’s been a lot of effective control, but that we are going to have the same challenges as everybody else as the weather gets worse, people are driven indoors, it’s harder to socialize outside, the temptation of pandemic fatigue sets in. I mean, all of these things are real and understandable and it’s just that they will lead to more virus transmission. So I think, like everybody, we’re gonna face challenges in the coming months. The kind of data that I think would be the most useful would be more detailed data on the testing, and on where the positive tests are coming from. And the state’s done a good job of some of that by sort of disaggregating based on the college versus noncollege and based on repeat tests versus first time tests. I think that could be potentially even better. And I think what’s really been lacking globally and I sort of suggested this was a failing of our national response, but that may have been a little unfair. But the failing of the global response is that we just sort of really detailed epidemiology of what kinds of places and why there is significant spread. I mean, we know meat packing plants and we know jails and prisons. But the sorts of places that lots of people go. And we don’t understand fully the amount of transmission. I find it strange that we’re still so far into this pandemic, relatively unclear about where the transmission is happening.

Q: Thank you.

MODERATOR: Next question.

Q: OK. Can you hear me?


Q: All right, thanks. I actually only have one question, but it’s sort of broad. The holidays are coming up and people are scheming various ways to try to safely gather, like if the whole family tests ahead of time, we quarantine for two weeks beforehand. A lot of us have relatives that may not even be with us a year from now. So in that context, is there any safe way to gather for the holidays? Is there any kind of a system that people can set up that would enable their families to do that?

MARC LIPSITCH: I think that’s a great question and something I’d like to think more about. I had a neighbor asked me. She told me what answer she wanted. She said, my family wants to get together for Thanksgiving. Twelve of us. And I think it’s a terrible idea. Would you please tell me it’s a terrible idea so I can quote you. And what I said was, well, I do think that many people in an indoor room that’s going to be heated and not ventilated very well, this is a risk. And I think, you know, there are a lot of things you can do short of having a big gathering of people, and I think time’s a wasting in the places that are that have cold climates. But, you know, one suggestion I made was to get a couple of those people at a time together in your backyard, roast a chicken, have stuffing, and call it Thanksgiving in October, while it’s still possible. That’s more possible here than some places and even more possible if you’re further south or whatever. I think that the principles are all the same of ventilation, outdoors, small groups. And staying at distance and masking. I don’t think that big holiday gatherings make a lot of sense. I think if people can figure out ways to do small ones following those rules and maybe Zoom or Skype in, other people from the family maybe do two of them in different places. I don’t know. I mean, I think people have a very real need to see their families. And you’ve got to figure out ways. But I think trying to be too clever and, you know, quarantining first and testing first, those will have some effect if they’re done very carefully. But most people can’t actually quarantine for two weeks before the holidays. So I would recommend doing as much socializing as you can outdoors, while the weather permits. That’s the idea I have. It’s not great.

Q: Yeah. There’s no way to test your way out of this if everybody tests negative. They’re not really safe to be together?

MARC LIPSITCH: Well, if everybody tests negative, I don’t know, I don’t want to invent something right now on the fly. I think it may be possible to come up with something with enough resources, enough testing and enough quarantining. But that’s a big undertaking. And if everybody does it carefully, that’s one thing. If everybody does it sort of, then that’s very different. So that’s giving me something to think about, let me ponder it, but I don’t want to give a half-baked recommendation, so to speak.

Q: Thank you.

MODERATOR: Next question.

Q: Thank you very much. So returning to what you were talking about, about the lack of detailed epidemiologic data. I’m just curious about what you see as why that’s the case. Where would that data come from in an ideal situation relative to what we had? What are the sort of failures that led to the situation and what could be done going forward to start getting that data in a more accessible and useful form?

MARC LIPSITCH: Yeah, well, I mean, at the very fundamental level, it’s a lack of testing. Well, that’s not the most fundamental. The most fundamental is that we have such widespread transmission right now in the United States and some other places, that it’s very hard to even know where people got exposed. And in the places that have been tracking that, the proportion of unknown source is going up, for example, Minnesota. So that’s the fundamental thing, is that there are so many cases now that it’s hard to track. The related problem is that there’s still a dearth of testing. So in places with a lot of private resources devoted to testing, such as many universities, you can actually really figure out where people are getting exposed and infected. You can do more detailed analysis of the incubation time and the latent period so that you can figure out, you know, when it might be safe to test out of quarantine. Those kinds of discussions are starting to happen. But the data to inform them ideally would have come from widespread testing at a population wide level. And from my understanding, there just aren’t such detailed data because tests have been at such a premium that you can’t do frequent testing. So the NBA and the colleges and some other institutions are going to provide data that would have been better to get in a much more timely since.

Q: Thank you very much.

MODERATOR: Next question.

Q: Hey, thanks for the call. It seems like there’s a familiar pattern where cases go up and hospitalizations and then deaths. With this possible winter wave, it looks like hospitalizations are already ticking upward. Do you have a sense of whether deaths will likely go up too, just given maybe better treatments? Maybe with mask wearing, there’s less of a viral load for some people. Do you have a sense of just with that third step, if more deaths will still occur this winter? Thank you.

MARC LIPSITCH: Yeah, I mean, I think that there is a lot of sort of hypothetical and circumstantial reason to expect the risk of death per case to go down. Partly that more young people are getting infected. But also, even in an age specific way, you would expect that better treatments and more speculatively, lower viral loads from masks, that’s a possibility, as you mentioned. And maybe earlier treatment and other things should be helpful. As far as I’m aware, there’s not really compelling data, when you slice it carefully by age, that shows a declining risk of dying. It’s very hard to tell because we don’t measure infections that well. But I have not seen compelling data that if you’re a person of age 70 who gets infection with SARS-CoV-2, your risk of dying is lower now than it used to be. I would expect that that is true. But I don’t see any compelling data showing it yet. I think that’s another important thing. Unless that risk is going down dramatically, of course, increasing cases will lead to increased deaths. It’s just a question of whether they’ll lead proportionally to quite as many. So I think it’s essentially inevitable that deaths will go up because cases are going up. And some of those will die. But whether there is a decline in the infection fatality rate, I would love to see the evidence. But I have not seen it yet.

Q: Thank you.

MODERATOR: Next question.

Q: Doctor, thank you for taking my question. A small study out of South Korea showed a pretty rapid decline in neutralizing antibodies to COVID-19, leaving open the possibility for reinfection. And I wonder if this has any implications for how well an eventual vaccine might work.

MARC LIPSITCH: Yeah, great question. I think all of these links are likely to be meaningful and all of them are still remained to be proven. It does seem that if you have neutralizing antibodies, you’re very likely to be protected against infection. The neutralization tests are variable between different approaches. Exactly what neutralization means, therefore, difference between studies, whether someone who once had neutralizing antibodies and no longer does has totally lost protection, unlikely that they’ve totally lost protection. But also it’s possible that they have lost some of their protection. So the interplay between immunologic memory, which is the ability to respond really quickly on a second infection and standing antibodies that are there, ready to neutralize virus immediately upon infection. That’s sort of something, not me personally, but scientists are trying to understand better in many different infections, including this one. And so I wouldn’t say that loss of neutralizing antibodies means those people are all ready to be reinfected. But clearly, there have been some cases of reinfection and clearly that is a factor after natural infection. So then the question you asked is about vaccines. And again, vaccines induce antibodies. They may also induce other arms of the immune system, and most of them do. And in many cases, vaccines induce considerably higher levels of antibody than natural infection, at least natural infection in most people. So I think it’s something to keep in mind, it’s something to try to measure, and it’s really important that studies of vaccines are not discontinued as soon as we have a little bit of data from them. We need to continue to follow up people and see whether their protection persists. But essentially, we don’t know the answer to your question. It’s a concern, but how it will play out, only the data will show.

Q: So it sounds like we’re going to have to continue to monitor the effectiveness of the vaccines once they are approved to determine how long they’re going to last.

MARC LIPSITCH: Yep, and ideally, we would do that by maintaining the randomized populations so we can look at continuing protection and the WHO, for example, has said that they will continue to follow people for at least a year. In other cases, people may end up getting the vaccine sooner than that, if they were in the control group. Probably not everybody because there will be limited supply and most people in the trials are probably not going to be the first in line for the vaccine. So I think there will be some ability to continue that follow up. But also we’ll have to look at the declines in antibodies and try to improve our understanding of how antibody levels determine or predict protection.

Q: Thank you.

MODERATOR: Next question.

Q: Thank you. Congratulations, doctor, again, and thanks for taking questions. I’m really glad you brought up the data, because that’s something that I’ve really been thinking about, is why don’t we have that data by now? And to your point about the global community, not necessarily having it as well. Why isn’t this happening? And should we have more data by now to be able to predict how to reopen or go about our daily lives better?

MARC LIPSITCH: I think we should, and it may turn out that what we think we know is really pretty much what there is to know. That airflow and crowding and masks and distance are the things and that it doesn’t really matter if you’re in a grocery store or a fabric store or a bar. What matters is the space and the ventilation and the amount of vocalization apparently elsewhere of course. Maybe that’s all there is to learn. But I think it seems to me that there is a need for better epidemiology. And I honestly don’t have a good answer for why. No country seems to have produced really detailed work on that. I mean, I think it may be partly the classic problem that the places best able to measure it are also the places best controlling it. And so they don’t have much data to measure. That’s a classic problem in infectious diseases.

Q: Really good point. And then really quickly on that, the CDC reports, I mean, they do offer some insight in sort of a piecemeal way, even though we have heard, of course, about ways in which they’ve been altered. So does that in any way offer some credible work or do we still have to be concerned about more broadly the take away from them and being able to apply that?

MARC LIPSITCH: Well, unless there’s a new piece out that I’m not aware of, the last thing I saw from the CDC was about a month ago and said that having contact with a COVID patient or eating in an indoor restaurant were the two risk factors they identified. You know, I think those are probably true, but they’re not very new. And they were based on about 300, 400 people, not a very large study. So it’s a start, but it’s not very informative.

MODERATOR: Next question.

Q: Hi. Thank you so much for doing this. I was wondering if you could address the question of how much the risk goes up as you add more people to a group. I’m also very interested in the holidays. There’s a lot of concern. And I’m wondering, well, you know, if you could address how much worse it is to be in a big gathering than a small one. And also, what you’re planning to do for Thanksgiving, whether you and your family have a plan to celebrate Thanksgiving.

MARC LIPSITCH: Yeah, well, I’ll take the second one first. We usually host about 16 people from my family, my wife’s family. And we’re not doing that this year, nobody’s traveling. They all come in from out of town and we’re just not doing it. And we’re very sad about that. But it’ll be the four of us, immediate family, having our Thanksgiving this year. The risk is a function of gathering size is actually something that a group of us are working on. And hopefully we’ll have a manuscript soon. But roughly speaking, the risk to each person goes up in proportion to the size of the gathering. So very roughly speaking, if there’s a half percent chance that each person’s infectious, and if you have, you know, five people, then there’s a two and a half percent chance approximately that at least one person is infectious and starts to change as the probabilities get higher. But roughly speaking, it goes up like that. Then also the chance that the number of people exposed goes up. So as a rule of thumb, if you double the size of the group, the amount of transmission risk goes up by a factor of four. If you triple, it goes up by a factor of nine because you have three times as many potentially infectious people and three times as many recipients. So that’s why the size of the group matters. And there are some subtleties to that are the things that we’re trying to work on. But that’s the rough calculation. And that’s why people have warned against large groups. And it also, of course, goes up in proportion to the risk, to the prevalence of infection in the places those people are coming from. So if you have a bunch of people from a high incidence place, then then there’s, of course, much more chance of transmission.

MODERATOR: Are you all set.

Q: So I did have one quick one. I wondered if you could just quickly address the role of viral genomics, in getting this kind of information about where it’s spreading, how it’s spreading.

MARC LIPSITCH: I have not followed that side of it as much as I would like to. This virus is relatively slow to change. So it’s not always clear if you have two virus isolates that are very similar. Whether that means that they are from a related chain of transmission or if they just happen to be similar by chance. So it’s better for ruling out transmission source than for ruling it in. I would suggest asking the question again when one of my colleagues like Bill Hanage is doing one of these calls because he’s done a bit of work on that. And it is something I generally like to do but have not followed due to lack of time.

Q: Thank you.

MODERATOR: Next question.

Q: Hi, good afternoon. I have a quick question regarding testing trends across the country. I want to know what you think about if we’re doing enough testing and what difficulties you’ve seen states and health agencies face when it comes to administering enough tests.

 MARC LIPSITCH: Yeah, I mean enough testing, of course, means enough testing for what? But if we really wanted to get things under control, then frequent testing of almost everybody would be one way to do it. And we’re, of course, nowhere near that. We’re doing infrequent testing of almost no one. And so I think, as I said, what we don’t have right now is a comprehensive answer for how to get from the high levels of community transmission. We have back down to very low levels without lockdown or without very intense social distancing interventions. To me, that is the task that lies ahead for people in our business is to figure out if there is such an approach. And I think testing would be at the center of that, but on a much, much larger scale than we have. And you can see that in places that have the resources to throw at it, like some universities and like the NBA and like Space X, Musk’s company, you know, you can control transmission with very extensive testing and compliance with isolation. The question is, is there an overlap between the amount of testing that we can realistically create and the amount that would be effective? And there’s been a lot of handwaving about that. But I think nobody is really confident about the answer. I would like to have an answer for you in a while from now, because I think it’s certainly a piece of the problem.

The other problem is, and this is not news, but the turnaround times for testing in some places remain a problem. It’s very hard to get answers quickly. And if you don’t know the answer for a few days, then those value of the information becomes much, much, much lower because the duration of peak infectiousness is much less than a week. So if you take several days, then it doesn’t matter what the answer was. You can’t use the information anymore. So faster tests, either PCR tests that can really give you the answer to same day or the next day and get it into the public health information system, or more rapid antigen tests that Michael Mina and others have been making the case for, are really essential. Otherwise, the data aren’t that useful. And I think that’s been much of a problem for contact tracing and many of the places that have tried to do it.

Q: Sure, that makes sense. I have another question for you. Do you think the rise in cases is related to a rise in testing, as the president often suggests?

MARC LIPSITCH: It’s partly related to that, but it’s mostly related to highs in the actual number of people ill. And you can see that in growing percent positive tests, which can’t happen just from doing more tests. And you can see that in the rising hospitalizations and deaths, which are more in some sense, not objective, but they’re much more consistent measures of disease activity because they’re not as dependent on tests. But that is part of the disinformation coming from the White House. And I’ve tried to stay away from making such bold statements, but the idea that when you have more people dying per day and more people being hospitalized per day, that that’s due to more testing is just not even logical, much less true. It’s just false.

Q: OK, great. Thank you, Doctor.

MODERATOR: Next question.

Q: Hi. Thanks so much for taking my question. So I wanted to go back to something you said about quarantine, because there are currently a few countries batting around the idea of reducing the quarantine time to 10 days or potentially testing out as a way to sort of make it less burdensome. And I’m wondering what the data says about the topic and what your thoughts would be on altering the quarantine period at all. Thank you.

MARC LIPSITCH: Yeah, that is one of the types of data that I think will begin to come out of colleges and universities. A colleague, Michael Springer, at Harvard Medical School, has been looking at this. And I think that the opportunities to shorten quarantine a little bit and to test out, will be real and will be one way that we can mitigate the impact of the people doing the right thing is that they don’t have to do the right thing for as long. Exactly the right number, I don’t yet know. I had a discussion with him yesterday about what the data look like, but they’re very preliminary and not carefully analyzed yet. So I think that will be an effort that is underway in the next couple of weeks as people gather that information. The reason why you need very detailed information is that you need to learn the distribution of something called the latent period, which is just the time from when you get infected to when you start to produce virus, which is probably sooner than you start to be sick. And the only way to know that is to have repeated tests on people over and over and over again. And then when you find out that they’ve been exposed, then you can start counting and continue to test them and see how long it takes. Those kinds of longitudinal tests of people who have been exposed just haven’t been happening in large enough numbers. But I think with universities, this is a real opportunity, because many universities are testing on a twice a week or three times a week basis.

MODERATOR: Are you all set?

Q: I’m all set. Thanks so much.

MODERATOR: Next question.

Q: Thank you so much, Doctor. I would like to ask you a little bit about what policies you might look to, to determine whether a state is pursuing herd immunity when the state is not openly suggesting it’s pursuing herd immunity. I don’t know if you’ve followed what’s happening in Florida, but on September 24th, the governor hosted a roundtable with two of the authors of the Great Barrington Declaration. And then the very next day, he opened up the state and basically opened up every part of commerce and required that local governments could not enforce mask mandates. So I wanted to just kind of get your senses to can we call that a policy of herd immunity here? What do you think?

MARC LIPSITCH: I would call it a policy that is counter to public health. And whether you call it a herd immunity policy or not, to me, is kind of secondary. I think herd immunity has become such a contentious term, that I’d almost say it confuses me more than it informs. I just was on Twitter, discussing as one word, I guess, with Alex Berenson, who’s been a provocateur in this space, another euphemism, saying, you know, because of something that I wrote about herd immunity to other viruses and bacteria a long time ago. People are just weaponized the word. And it’s not even clear how much herd immunity will be generated by infection, depending on how long the immunity lasts. So I think the real discussion is, do we let up completely or largely on all control measures, to block the spread in the general population or not? And so I would call it leave the population at risk strategy, and that seems to be what you’ve just described, and that is counter to the goal of trying to minimize disease and severe disease and death from this virus.

Q: So if I could just have a quick follow up. The conclusion here in Florida is that we’re going to open everything up, we’re going to encourage schools, you know, even on to the point of threatening to reduce funds for schools that don’t open fully. What are the triggers or the measures that we should be taking to hold them accountable to whether this policy is being counterproductive or not? And I think I know the answer to this, but I guess if you could just summarize it in your words.

MARC LIPSITCH: I mean, the ultimate measures are, does the health care system lose function because hospitals and especially intensive care is overwhelmed? And how many people die? The problem with those triggers is that they are, as we’ve discussed, delayed. And so by the time those things happen, if you respond, then you have to endure them happening for another several weeks before the response has an effect. So prudence is to anticipate that rising numbers of cases will lead to those things. But some people, particular politicians and not only politicians, have resisted the idea that we can draw the line from cases today to deaths tomorrow.

Q: Thank you.

MODERATOR: Next question.

Q: I’m going to ask my follow up question first and then asked my question, and that is, are we getting better at treating the virus? And the reason I’m asking my follow up question first is my question is The New York Times data today shows that at 14-day change and a 30 percent increase in cases, but minus one percent decrease in deaths. So my question is, is that just data at this moment or now that we’re seven to eight months in, even though we’re going to see an increase in cases, are we going to see a decrease in deaths? And does that have anything to do with how well we know how to treat the virus?

MARC LIPSITCH: We will see an increase in deaths corresponding to the increase in cases. How much and exactly the timing? It’s going to be delayed, but it’s also a very complicated function because you have different states that are going up and down, different age distributions and comorbidity distributions and access to health care in different states that are having rising or falling numbers. And so all of those determine, with a delay, whether our cases are more or less likely to result in a death. So the big rise in cases will give rise to a big rise in deaths. As I said earlier, the question is whether we’re getting better in the sense that for every case, the number of deaths for every, say, thousand cases, the number of deaths is going down. And again, the right denominator for that is the number of infections, not the number of detected cases. And that’s another wrinkle on this question of how cases translate into delayed deaths. As I said earlier, I don’t see population level evidence that we’re getting better at treating COVID-19. Clearly, steroids help, dexamethasone helps. And less clearly, probably Remdesivir does something and some other approaches that are not that are not drug treatments, I am told also make a difference. So at the individual level, it seems like we should be getting better. And the data that show that impact at the population level so far, have not been generated, to my knowledge.

Q: Could I just ask a quick follow up? Could you do this at the individual level where, for example, early on in the pandemic, people were anxious or might not have gone to the hospital, called their doctor. Is there anything that you’ve seen in terms of the relationship of the individual who is infected to accessing the health care system that might result either on an individual level or in a population level, in their having an improved outcome? Like have we, or maybe the question really should be posed as have we learned anything in eight months that’s going to help the individual patient and the population?

MARC LIPSITCH: I mean, it seems like we’ve learned some things that will help the individual patient, and I believe that is having an effect on the population. But I don’t see the data yet to show it, and maybe it’s not a big enough effect, maybe there are countervailing effects. But you know, I don’t have an answer for you beyond, it seems likely that it’s true and the data so far just don’t exist, I think. And I think ultimately the only data that will be really compelling our population level data in the sense that case ascertainment is changing and it’s changing in so many ways that we don’t understand that just knowing who gets tested positive is a poor proxy for infection and remains a poor proxy. So I think the deaths divided by serological proven infections is really going to be the best measure. There will be proxies such as hospitalization, fatality rates and other things that would sort of adjust for under ascertainment. But ultimately, I think it’s going to be population level data.

Q: Thank you.

MODERATOR: Dr. Lipsitch, looks like we have about five minutes left and three questions. Do you have any flexibility with when you stop today, or do you have to go?

MARC LIPSITCH: I can take the three questions.

MODERATOR: Thank you so much. Next question.

Q: Hi Doctor, I’m coming in from Columbus and there’s a rumor mill has come and gone through the pandemic, but it’s now at the crux of a federal lawsuit here. But it really comes back to the fact that CDC says only six percent of coronavirus deaths come without any comorbidities and therefore the theory goes, ninety four percent of the death toll is not actually due to the coronavirus. Have you encountered this theory and how do you respond to it when it comes up?

MARC LIPSITCH: I hadn’t heard that specific number. But, many of these deaths are in excess of what you would expect. And indeed, everybody’s death is preordained from the fact that they were born. They’re going to die sometime. And most of us have some other illnesses besides whatever infection there is. It’s just wrong to say that the coronavirus doesn’t cause the death of someone who dies earlier than they would have otherwise died. Even if that person had some other disease, because that’s just what it means to die if something is to die earlier than you otherwise would have from whatever other thing would have killed you. I mean, it’s just nonsense.

MODERATOR: Did you have a follow up?

Q: I think you got it. Thank you. Much appreciated.

MARC LIPSITCH: I might just add. The flu and seasonal flu, most of the people who die of seasonal flu, if you look at their stated cause of death, it’s a heart attack or a stroke or some other circulatory problem. But the flu killed them. And the one way we know the flu killed them is that those happen not only during the weeks of the year, each year, which are different from year to year when there’s most flu activity, but also the number of those deaths is higher in years with some flu strains. When the more severe flu strain, each is predominant and when the milder flu strain, each one is predominant. There are all sorts of types of evidence that we can use to say that person wouldn’t have died then if it wasn’t for the flu. With COVID, it’s probably not even like that. It’s probably just that the course of the illness is more severe because you have, say, diabetes or something like that. But infectious diseases kill people who are sick otherwise. But that doesn’t mean that those people were killed by something else. They were killed by the infection.

MODERATOR: Next question.

Q: Hi Marc, what is the current estimated impact of seasonality on the reproduction number of the virus? And what are thought to be the causes? I’ve seen a lot of different speculations, including UV light and things like that, and wondered if you could speak about those.

MARC LIPSITCH: Yeah, I haven’t seen very much further work since the first burst of it back in the spring. And the short answer is, we don’t know either the magnitude or the mechanisms. The longer answer is that based on other coronaviruses, we estimated that about a 20 percent difference between the peak and the trough in transmissibility. Others got similar estimates from their attempts to figure out what’s going on with this coronavirus, which, of course, you know, were plagued by all the usual problems of data with this new virus. But that was a fairly typical estimate. The reasons for it are also uncertain. And as you mentioned, UV light is one that people have hypothesized for flu. We have much better evidence that it’s absolute humidity that drives a lot of it. The amount of water in the air, less is good for the virus, bad for us, and there’s less of it in the winter. And then there’s the behavioral factors, which I think based on what else we know about the epidemiology, will become important, with just being indoors more. And so I think there will be a seasonality that’s partly due to the fact that we just can’t distance as well indoors. So I think all of that will contribute, and I think we remain uncertain about the exact magnitude.

Q: Thank you.

MODERATOR: OK. It looks like the last question.

Q: Hey, thank you. Can you hear me?


Q: All right. Thanks, Dr. Lipsitch, for your time. I’ll try to be brief, but one other thing here. You know, I’ve watched the case numbers, the positivity on testing, and the hospitalizations quite closely. And the governor himself has brought up this idea of, you know, he calls it herd immunity. But I think I’ve understood it to be partial population immunity and certain aspects, especially Miami-Dade, certain aspects of Florida’s population. And it seems like that’s part of their understanding of what’s happening and why we have not seen a rise in Florida. And I just kind of wanted to run that idea by you. I’ve talked to your colleague, Dr. Hanage, about this. I’ve talked to Dr. Bloom about this. But, you know, here we are kind of well into October and we’re not seeing a rise here in Florida, even while other parts of the country are seeing those rises. So I just wanted to get your help understanding kind of, is this just a wait and see or, you know, how you would explain that?

MARC LIPSITCH: I think there were a chorus of people saying when it seemed that there were dozens of places around the world that were not having big rises in the summer. A lot of people said it must be herd immunity. And now the list seems to be Florida and Sweden that people are pointing to because everybody else’s had a take-off. I mean, there’s no doubt that if 10 or 20 or 30 percent of the population gets infected, that will slow transmission. And I’m sure there are pockets of Florida in which that is a noticeable effect. The estimates of how many people have to get infected before pre pandemic levels of activity can be possible without continued transmission are much more like 60, 70 percent. Maybe 50. But probably not in the most densely packed areas. There is some kernel of truth there that probably some populations are being partly protected by the immunity that has been built up. Almost anybody would agree to that. The question is whether it’s prudent to have to rely on that, given that, you know, and I’m pretty sure in October, it’s still pretty nice time to be outside. People are not spending much time indoors, in Florida compared to other places. And, you know, as the winter comes, there are many reasons to expect transmission to increase. So. You know, it’s not nonsense to say there is some herd immunity right now. It is nonsense to say that means we’re out of the woods.

Q: And just one last point on this, we I think we spoke on a call not that long ago where I’m apologize. I’m not sure if this was you or your colleague. Dr. Hanage also mentioned seasonality and how that might be affecting things in Florida. I believe that they said that without that seasonal affective, the, you know, this pandemic, that there might have been even more transmission during our July spike. I mean, given that you brought up weather patterns, I guess my question is just do we have any better understanding of how seasonality might be affecting transmission, given kind of where we’re seeing the biggest spikes in other parts of the country?

MARC LIPSITCH: I haven’t seen a good analysis, but it may have been done.

Q: OK. Thank you so much.

MODERATOR: It looks like that’s our last question. Dr. Lipsitch, do you have any final thoughts you’d like to share with us?

MARC LIPSITCH: No. Give me, as always, lots to think about. Thanks for the questions. And talk to you again sometime soon.

This concludes the October 19th press conference.

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