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

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. 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 reopen 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.

Or they've developed enough community immunity that they're no longer having the pandemic because they have enough immunity in New York City to actually stop.

I challenge that, uh, Senator, because I want— please, sir, I would like to be able to do this because this happens with Senator Rand all the time. You were not listening to what the director of the CDC said, that in New York it's about 22%. If you believe 22% is herd immunity, I believe you're alone in that.

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.

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 virus rip among young, healthy people and protect the vulnerable is that wrong idea when it comes to COVID.

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.

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

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.

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

There are certain diseases that do saturate society. Examples include measles and chickenpox, where 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 children. Herd immunity 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.

So basically you have these short periods of herd immunity followed by cycles of spikes of infection and disease.

Exactly.

In fact, with measles, traditionally it's an every 3-year cycle, which is a reflection of the population dynamics of people being born and becoming susceptible.

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

It's ironic that Sweden, which is a social democracy that has a very progressive social network, 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 3, 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.

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 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?

That would require the deaths of at least 500,000 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 than were killed in all of the wars of the 20th century. Now, in terms of how realistic the 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 5 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.

So herd immunity also assumes, at least the mathematical 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?

What it means is that any one 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 a society and still a lot of people and a lot of communities or 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.

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?

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, 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 1 or 2 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. 1 in 5 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 that 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 half a million more deaths. And herd immunity might even require more than that. So there is no quick fix to this pandemic, but we can do much better if we work together.

How are we doing in comparison to other developed countries in the world? How is the United States doing?

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 US has had. The bottom line is a competent response in the US could have prevented many, if not most, of the more than 200,000 deaths that there have been in the U.S.

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

We really need a one-two punch, 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. There's a lot we can do to do more safely, whether it's schools or workplaces or healthcare 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.

Tom, thanks so much for joining us again on The Epidemic Podcast. You were one of our very first guests, I think in episode 2, and it's great to have you back.

Thanks, Celine, and it's great to speak with you again. Thanks for what you do.

After the break, we'll continue our episode about the herd with Dr. Marc Pagel.

Today, it's my great pleasure to have on the podcast Dr. Mark Pagel. Mark is an evolutionary biologist and a professor at the University of Reading. 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.

So Mark, I want to start with asking you 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 why those tribes are forming in the first place.

Humans have sort of explored the earth in these little cooperative 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. And 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 away as coming from a certain area. And so humans really are tribal in this way, probably in a way that no other species is.

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 social affiliations?

This is a really, really difficult subject. Humans seem to be a species in which We have evolved these psychological tendencies to look out for our societies, 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. 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 well-being of the group of chimpanzees it lives in.

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

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.

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?

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 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.

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?

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. So we're willing to engage in these kind 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. And so that will be a motivation for me to join in. With that campaign. And then secondarily, but, you know, in close succession, also appealing to people not to harm others, because that is a very powerful moral or ethical principle in human societies.

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?

So 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, and you're not expecting anything back. Our societies 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 masks because I want to advertise to people that 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 we'll all simply wear masks. That's what governments are desperately trying to do. They're desperately trying to convince us that we should wear masks simply because it's the right thing to do, and You know, 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. And, you know, killing another person is probably the most strongest prohibition we have. And so perhaps that has worked somewhat.

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?

There has been this sort of polarization, especially in American society, and, and some groups are seeing wearing of masks as a patriotic thing to do because it improves the public health of the nation. Other groups are seeing wearing a mask, for example, as a 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.

In your book, you say that the more arbitrary the norm or signal of group commitment, the more powerful that signaling is. You know, and I again go back to wearing masks. Why is it that maybe the seemingly more arbitrary, that that signal becomes more powerful.

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. 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 real member of my group. They're willing to take risks to be part of my group. And so not wearing a mask could in that sense be indeed be a very powerful measure of tribal identity.

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

They're probably very effective, and yes, 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. And 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's 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, then I think it will backfire very, very badly. So I think it has to be applied very, very carefully. It can't come from above. I think it needs to rise up out of our societies naturally.

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

Thanks very much, Céline.

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