S1E48: A False Promise: Herd Immunity and Herd Mentality / Mark Pagel & Tom Frieden

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“I would put this in very plain English: The way to protect the vulnerable is to have fewer infections, not more infections.” – Dr. Tom Frieden

Talk of achieving herd immunity without a vaccine is back in the news, despite the consensus among public health experts that this approach would cost hundreds of thousands of American lives. Former CDC Director Dr. Tom Frieden talks about his recent op-ed against this approach and the “one-two punch” to get the pandemic under control.

Then, evolutionary biologist Dr. Mark Pagel explains why some of the traits that make humans so successful as a species are getting in the way of an effective response to the pandemic, especially when it comes to wearing a face mask.

This podcast was created by Just Human Productions. We’re powered and distributed by Simplecast. We’re supported, in part, by listeners like you.

Tom Frieden: There is no evidence to suggest that allowing people to get infected is going to be a good route to sooner economic recovery

Celine Gounder: Welcome back to EPIDEMIC, the podcast about the science, public health, and social impacts of the coronavirus pandemic. I’m your host, Dr. Celine Gounder.

Celine Gounder: Herd immunity is something people have been talking about since the beginning of the pandemic. It’s the idea that when enough people are immune to a disease, transmission slows to the point where it’s no longer a threat. There’s just not enough other people to infect, and the disease dies out. But trying to achieve this without a vaccine is controversial. Proponents of so-called “natural” herd immunity say this strategy will allow the economy to re-open and get children back to school. Some of the most heated public debates about it have been between Senator Rand Paul and Dr. Tony Fauci.

Celine Gounder: This approach has been widely criticized by a majority of public health experts. But the herd immunity strategy has gotten a boost recently. On October 4th, something called the Great Barrington Declaration was released. It calls for lifting all pandemic control measures. The three original signers of the declaration were invited to Washington, D.C. by President Trump’s coronavirus advisor, Dr. Scott Atlas, to discuss their plans with Health and Human Services Secretary Alex Azar.

Tom Frieden: It’s been said that for every difficult problem, there’s a solution that’s quick, simple, and wrong, and the idea that we should let this, the, uh, virus rip among young, healthy people and protect the vulnerable is the wrong idea when it comes to COVID.

Celine Gounder: This is Dr. Tom Frieden. Tom was the Director of the CDC from 2009 to 2017. Today, he’s the President and Chief Executive Officer of Resolve to Save Lives. Tom wrote an op-ed in The Washington Post arguing against the Barrington Declaration and herd immunity without a vaccine.

Tom Frieden: And I would put this in very plain English: the way to protect the vulnerable is to have fewer infections, not more infections.

Celine Gounder: In this episode we’re going to take a look at two ideas at the core of many debates on how to address the pandemic: herd immunity and herd mentality. We’ll hear more from Dr. Tom Frieden and then we’ll hear from Dr. Mark Pagel. He’s an evolutionary biologist who will explain why some of the traits that make humans so successful as a species are getting in the way of an effective response to the pandemic, especially when it comes to wearing a face mask. So, let’s get back to our conversation with Dr. Tom Frieden.

Celine Gounder: Has herd immunity ever been achieved without a vaccine? I’m thinking about the very long history of smallpox, for example, here.

Tom Frieden: There are certain diseases that do saturate society. Examples include, uh, measles, and chickenpox where, uh, in a natural state, virtually everyone gets infected with them. But then what happens is new people get born and the disease continues to circulate. And so there continues to be a lot of spread to, uh, children. Herd immunity, uh, can occur through universal infection, but it’s only going to last for a little bit of time until more people get infected unless the pathogen is truly eradicated, and that has only been done with smallpox.

Celine Gounder: So basically you have these short periods of herd immunity followed spikes of infection and disease.

Tom Frieden: Exactly. In fact, with measles, traditionally, it’s an every three-year cycle, which is a reflection of the population dynamics of, uh, people being born and becoming susceptible.

Celine Gounder: What would you say to those who point to Sweden as a success with respect to the herd immunity approach?

Tom Frieden: It’s ironic that Sweden, which is a social democracy, that’s, has a very progressive social uh, network, uh, is being pointed to by very conservative commentators as a success story here. And I think there’s a lot that’s confusing about the data from Sweden. One of the things is that they say they were never attempting herd immunity and they’re nowhere close to it now. Two is, they haven’t done particularly well. They have a death rate that’s 10 times the death rate of their neighboring country. And three, it didn’t really help their economy. Their economy is not doing any better than their neighboring economies. So they traded a lot of death for no real benefit. It’s certainly neither a success story in terms of COVID, nor an example of using a herd immunity approach.

Celine Gounder: So my next question is really having you walk us through the numbers you had in your Washington Post op-ed recently. So let’s say for argument’s sake that after someone has COVID, they do develop strong and lifelong immunity and that that’s a big assumption there. And then let’s say that herd immunity kicks in at 60% infection of the population. And let’s say the fatality rate is 0.5% among those who are infected. So, first of all, how many more Americans would die, assuming all of those assumptions are correct, how many would die before we reach herd immunity?

Tom Frieden: That would require the deaths of at least a half, a million more Americans, maybe 600,000, maybe twice that. There’s still a lot we don’t know. And just to give you a sense of scale, that would mean more Americans killed by COVID in about a year, year than were killed in all of the Wars of the 20th century. Now in terms of how realistic that assumptions are, not very. It’s unlikely that everyone with COVID infection develops strong and lifelong immunity. And we don’t know that it’s going to be a 60% threshold to getting to that level. And, furthermore, even if you had a high level of immunity, you’re still going, to have outbreaks and clusters, this is not going to go away. We need to essentially go through the five stages of grieving and recognize that we are not going back to a pre COVID world anytime soon, the fact is we’re going to have to adjust much of what we do for the long-term.

Celine Gounder: So herd immunity also assumes at least the mathematical, um predictions or calculations of that assume random mixing, but what if populations mix non-randomly? Does that mean some pockets could achieve herd immunity more quickly than others? And what would that mean for overall population immunity?

Tom Frieden: What it means is that anyone person in a community is not equally likely to have contact with any other person. What that means is, there are pockets in society, groupings and so you could have a very high infection rate in this society, and it’s still a lot of people and a lot of communities are sub-communities that have low infection rates. That’s why this kind of theory of herd immunity is very problematic because even if we got to a high level of immunity from vaccines and natural infection, there will be pockets that are susceptible to explosive outbreaks. And one of the things that’s really interesting and unfortunate and what we’re seeing now in New York City and in parts of Europe as well is that the communities that were hardest hit are hardest hit now. So there were certain academics with no evidence and no real infectious disease experience who were saying, Oh, herd immunity is going to come at 20 or 30 or 40%. That’s clearly wrong because we now have societies and communities that were hit very hard and are having explosive spread now.

Celine Gounder: Why is it we can’t shield the elderly and others who have underlying risk factors. You know, why can’t we just protect the vulnerable? What would it take to do that?

Tom Frieden: First, although younger people rarely get seriously ill, they do sometimes, and they can die. That’s not even to mention the long haul effects, which may linger for months, or we may find out, for years. Second, what starts in children and young adults doesn’t stay with them. No age group is an Island. Young people have parents, they have grandparents, they shop, they work and when they interact with others, they spread infection, even if they feel perfectly fine. And that’s exactly what we’ve seen in the US. Infections in younger adults followed one or two weeks later by hospitalization and followed by increasing deaths. Third, we don’t know if immunity will be strong or long-lasting, even if lots of young people get infected, they’re not going to be a wall to protect the rest of us. Fourth, the vulnerable aren’t a small group. One in five Americans is over the age of 60 and more than 95% of older people don’t live in nursing homes where there are policies that could reduce risk and half or more of all adults by some estimates have health problems that could increase their risk of death from COVID and the bottom line then, is it getting enough people infected to achieve herd immunity would come at a terrible price. With less than 15% of Americans already infected, we’ve had over 220,000 deaths. to get to a 60% infection rate would mean at least a half a million more deaths. And herd immunity might even require more than that. So, uh, there is no quick fix to this pandemic, but we can do much better if we work together.

Celine Gounder: How are we doing in comparison to other developed countries in the world, the United States doing?

Tom Frieden: The U.S. is a laggard. We have a much higher mortality rate than countries that have done a good job. And that includes vastly higher than countries in Asia that have crushed the curve, whether you’re talking about Taiwan or Singapore or Hong Kong or Australia or New Zealand. But also we’ve done not nearly as well as countries like Germany and Canada that have a fifth or a half or less the death rate, the U.S. has had, The bottom line is a competent in the U.S. could have prevented many, if not, most of the more than 200,000 deaths that there’ve been in the U.S.

Celine Gounder: So, what do we do to knock down the spread of the virus and how do we contain the virus?

Tom Frieden: We really need a one, two punch. Um, and really there is a lot of progress here. Although masks are getting a lot of controversy. If you step back. Let’s in public health take yes for an answer. 80 to 90% of people are wearing masks in public indoor spaces. Yes, we can do better. Yes, we can track it. But ultimately this is a huge behavior change in just a few months now that it is clear that masks protect others and likely protect you as well. Uh, there’s a lot we can do, to do more safely, whether it’s schools or workplaces or health care or outdoor activities, but we’re going to have to have this one, two punch. The first is to knock down spread of the virus and that’s with the three W’s: Wear a mask, Watch your distance and Wash your hands and also reduce risky indoor spaces with poor ventilation. And unfortunately, that includes bars and restaurants, especially where COVID is spreading widely. And further, figure out where it’s spreading in your community, so you can then stop those amplification points. The second punch is to box the virus in so that we can prevent cases from becoming clusters and clusters from becoming outbreaks. If we isolate people soon after they get infectious, they will spread less virus. If we quarantine people soon after they’ve been exposed, then if they do develop the infection, it will stop with them. That one, two punch can drive infections down. And that in turn is really the only way to resume economic and social activity.

Celine Gounder: Tom, thanks so much for joining us again on the EPIDEMIC podcast. You were one of our very first guests, I think in episode two and it’s great to have you back.

Tom Frieden: Thanks, Celine. And it’s great to speak with you again. Thanks for what you do.

Celine Gounder: After the break, we’ll continue our episode about the herd with Dr. Mark Pagel.


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OK, back to the show.

Celine Gounder: Today, it’s my great pleasure to have on the podcast Dr. Mark Pagel. Mark is an evolutionary biologist and professor at the University of Redding. He studies how evolution imprints on human behavior from genes to language and culture. And he’s the author of one of my favorite books, Wired for Culture. 

Celine: So Mark, I want to start with talking about why humans form tribal groups. As a public health expert who’s very much involved in, in the coronavirus pandemic, it’s been very challenging to communicate and to cross sort of political divides in the United States. And I think it would be helpful to understand, um, why those tribes are forming in the first place.

Mark Pagel: Humans have, have sort of explored the earth in these little co-operative societies that we in a kind of shorthand refer to as tribes. And all manner of rules and sort of personality or psychological traits have sprung up in us to make sure those small groups work. One of the strongest and can lead to some of the most disturbing outcomes is that we’ve evolved a whole lot of tendencies for and abilities to identify people that we think are in our group. And some of them are obvious like skin color or facial shape. Others are less obvious, like an accent that you have. Those things give you a way as coming from a certain area. And so humans really are tribal in this way, probably in a way that no other species is.

Celine Gounder: And so a question that’s more directly, you know, applicable to the current pandemic. Why do people risk their health and even their lives on behalf of their culture, their, their social affiliations?

Mark Pagel: This is a really, really difficult subject. Humans seem to be a species in which we have evolved this, these psychological tendencies to look out for our societies and, and the most vivid examples of that are when we go to war and fight for our societies. And this kind of altruism seems to be widespread in human societies.

Mark: This is a personality trait that humans have that you just don’t see in other animals, you would never expect a chimpanzee to go around worrying about how it can improve the wellbeing of the group of chimpanzees it lives in.

Celine Gounder: So why is it that people might choose not to wear a mask, even though the science would indicate that that protects them and, and others in the midst of the pandemic.

Mark Pagel: It comes back to the psychological traits that we’ve evolved as a species. This, this strong need to identify and to advertise the group that we belong to because we think in doing so, we attract other like-minded people to be around us. And, we notice this with the groups of people who don’t want to wear masks, they’re quite vociferous about it. It isn’t just that they’re quietly going about their business, but they want it to be known that they’re not a mask-wearer and in some sense, this attracts like-minded people to them.

Celine Gounder: Why is it whether it’s politics or science, you know, why is it we’re best persuaded by our family and friends rather than science and facts?

Mark Pagel: Yes. I think we have to be aware that we go through life taking direction from other people. Most of us have to make decisions about things on a daily basis that we really don’t have the information to, to make the correct decision about. If you look around you at any given time, the ideas and the behaviors that you can observe are ideas and behaviors that by and large have kept the people alive who have them. And so in a sense, I think that we follow those who are most close to us in terms of our family or in terms of the tribal identities we have, and we look to what they’re doing and we just take it on board, that those are going to be reasonable things to do. It’s a kind of predisposition we have as a species.

Celine Gounder: There’s been a lot of back and forth among public health leaders about how best to message about masks. Is it to say, it’s to protect yourself? Is it to say, it’s to protect others? Which message is more convincing and why?

Mark Pagel: Typically, our first allegiance is to ourselves, and so we probably want to convince people that wearing a mask will protect them. And then I think our second allegiance is going to be to our society. To the extent that we think our societies are going to be organized in a way that will bring us good. We’re willing to engage these kinds of altruistic acts like wearing a mask if we think that if everybody wears a mask we’ll all be better for it. So we’re not willing to do it simply to help others but if we think we’ll all be better for it. So one of the benefits that might come from everyone wearing masks is that I, personally, will be less likely to get coronavirus. So, that will be a motivation for me to join in with that campaign. And then secondary but, you know, in close, um,  succession, also appealing to people not to harm others, because that  is a very powerful moral, or ethical principle in human society.

Celine Gounder: One of the arguments for mask-wearing has been to protect yourself, but it’s also to protect others. What is reciprocal altruism and how is that different from altruism?

Mark Pagel: So a, a pure altruistic act might be putting on a mask to go out shopping simply because you think it’s wrong to expose others to a virus that you might be carrying. You’re not expecting anything back. Our societies are, are based on an even more abstract form of altruism that we call indirect reciprocity. So, mask-wearing becomes a value. I don’t wear a mask in front of you just so you’ll wear a mask in front of me. I wear a mask because I want to advertise to people I’m a mask-wearing kind of person that that’s an important thing to do. And then I’m hoping that others will adopt that value and will all simply wear masks. That’s what governments are desperately trying to do. They’re desperately trying to convince us that we should wear a mask simply because it’s the right thing to do and one of the most effective messages I think in that campaign has been to say that you could kill somebody if you didn’t wear a mask. Killing another person is probably the most strongest prohibition we have. And so perhaps that has worked somewhat.

Celine Gounder: So I would say personally that wearing a mask is patriotic. That it’s something that’s for the good of my community, for the good of my nation. Why is it that wearing a mask might not be seen as patriotic by somebody who’s conservative?

Mark Pagel: There has been this sort of polarization, especially in American society. And, and some groups are seeing wearing a mask as a patriotic thing to do because it improves public health of the nation. Other groups are seeing wearing a mask, for example, as, uh, statement that you’re not a member of their tribal group. And so we can see again, that depending upon the tribal identity, that one is adopting we can get completely different behaviors and actions and beliefs

Celine Gounder: In your book, you say that the more arbitrary the norm or signal of group commitment, the more powerful that signaling. You know, and again, going back to wearing masks, why is it that maybe the seemingly more arbitrary that, that signal becomes more powerful?

Mark Pagel: So the more arbitrary they are tells me that somehow they’ve really adopted those behaviors because they want to demonstrate their commitment to my tribal group because they’re not getting anything out of those. They’re not benefiting from them in any other way, other than to advertise that they’re a member of a group.

Mark: [00:53:09:24] And the very risk that’s associated with that tells me if I’m looking for other people, I want to know are a part of my group. It tells me that they’re probably a, a real member of my group. They’re willing to take risks to be part of my group. So not wearing a mask. It could, in that sense, indeed be a very powerful measure of tribal identity.

Celine Gounder: So, what about how we enforce some of these norms? Um, shame and, and stigma are often used, you know, in addition, to say, mandates or fines. Are shame and stigma, useful tools and, and enforcing such behavior. And when they’re targeted, say at the individual versus at a group, how effective are they and can they backfire?

Mark Pagel: They’re probably very effective and yes, they, they can backfire. I mean, what has to happen is that shame needs to come from the group that we hope to be a part of. If we can get enough people in that group, our immediate society, the people that we spend time with to be sort of in a sense, threatening to ostracize us, we will come around because we don’t want to be excluded from that group. And so if that shame can arise sort of naturally out of one social group. I think it can be very, very powerful. If it feels imposed upon us, especially by people we don’t identify with people who aren’t in our group. Oh, those people who think wearing masks is important. Then I think it will backfire very, very badly.

Mark Pagel: So I think it has to be applied very, very carefully. It can’t come, come from above, it needs to rise up out of our societies naturally.

Celine: Well, Mark, thank you so much for speaking with us.

Mark Pagel: Thanks very much, Celine.

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I’m Dr. Celine Gounder. Thanks for listening to “Epidemic.”

Mark Pagel Mark Pagel
Tom Frieden Tom Frieden
Dr. Celine Gounder Dr. Celine Gounder