The Daily - Why Herd Immunity Is Slipping Away

Episode Date: May 7, 2021

From the earliest days of the pandemic, herd immunity has consistently factored into conversations about how countries can find their way out of lockdowns and restrictions.Now, many experts believe that the United States may never reach the requisite level of immunity.We explore why, and what it might look like to live in a country where there is no herd immunity against the coronavirus.Guest: Apoorva Mandavilli, a science and global health reporter for The New York Times. Sign up here to get The Daily in your inbox each morning. And for an exclusive look at how the biggest stories on our show come together, subscribe to our newsletter. Background reading: The emergence of widely circulating coronavirus variants and persistent hesitancy about vaccines will keep the goal out of reach. The virus appears to be here to stay, but vaccinating the most vulnerable may be enough to restore normalcy.For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.

From The New York Times, I'm Michael Barbaro. This is The Daily. From the beginning of the pandemic... There's been a lot of talk of herd immunity. Herd immunity. Herd immunity. Public health officials said that achieving herd immunity... Herd immunity is what's going to save the country from an endemic pandemic.

...would mark the end of the crisis. If you get an overwhelming majority of the people vaccinated, we can reasonably quickly get to the herd immunity that would be a blanket of protection for the country. Today, as infections fall and the country begins to fully reopen, my colleague Apoorva Mondavili on why experts now believe that achieving herd immunity may not ever happen. It's Friday, May 7th. Apoorva, describe this reporting that you have been doing over the past few weeks.

I had been thinking about where we are with getting to the end of the pandemic, right? We've been talking about getting to herd immunity as this percentage of population that we have to get to, this milestone beyond which the virus is going to have a lot of trouble spreading. So it was always described to us as the way out of the pandemic, as this place where we can finally show the virus the exit door and can get on with our lives. And I wanted to talk to some scientists to see how close they thought we are to this herd immunity

threshold where the virus basically has run out of people to infect. Right, which is an extremely pertinent question. Are we nearing the point at which if somebody sneezes near you and has COVID-19, that sneeze is just going to bounce off immune people, right? People who are immune because they've been vaccinated or they've had an infection. And basically, the virus can't find a host. Yes, exactly. Hello. Can you hear me?

I can hear you. Hi, how are you? Hi, Aparuva. So I called up a bunch of scientists across a range of disciplines, and I asked them that question. So let me start by just saying, you know, do you think that we will get to herd immunity? How close are we to that point?

And what did they tell you? It was a very dispiriting conversation. So we probably won't get to herd immunity. I think that's really uncertain and unlikely in the near future. I don't think that reaching the herd immunity is the way that we're most likely to get out of the pandemic. Person after person that I called told me that not only were we not that close, but that we may never get there. that we're unlikely to ever get to the point where we can eliminate SARS-CoV-2 altogether through herd immunity. That must have felt like whiplash.

It was a shock because not only did they say this to me, but it seemed like they had all been thinking about this for months. They had all known this for months. And it felt like, well, why haven't you told us that then? We may never actually get to this herd immunity threshold. Well, let's talk about how we've arrived at this moment, this very sobering moment where it seems that herd immunity might not ever happen. Because my sense, and I think it's our collective sense, is that we were on our way towards herd immunity and it was achievable. So how did we get to a point where it's now looking not at all achievable? You're not alone. I think everybody thought it was achievable. And we started talking about this

pretty early on in the pandemic. You know, I remember writing about antibody tests when they were first coming out on the market in April and May last year. Already, the conversation was very much about, we are trying to measure people's immunity because this is how we're going to know how many people are protected and how close we are to herd immunity. The conversation started right then. and it stayed with us. You know, the estimate around then was always 60 to 70 percent. And it stayed at that level until the summer when people actually revised it downward. Even some very cautious scientists, whom I consider to be, you know, very careful and circumspect in their thinking, even they started to say, well, maybe we can actually achieve herd immunity by 45 percent, 50 percent. And just to explain what you mean when you

mention those percentages, this is the percentage of Americans who needed to achieve immunity for the pandemic to more or less start to come to an end. That's right. And that percentage included both people who are vaccinated and people who had just been sick and had recovered and now had some kind of immunity from the virus. So it seemed really achievable because first of all, we had infections in very big numbers. So it seemed like, you know, in cities like New York, so many people had gotten sick and recovered that, you know, in pockets of the city at least we might already be at herd immunity and this was just you know such an attractive idea right you can see why

it was so appealing everybody wanted to think we are so close to the end of this thing and in New York after we had been through such a horrific horrific spring we just wanted to feel like it's done we're through the worst so that the summer. And then the vaccine started to become a reality. We started to see that Pfizer and Moderna had great results. They were showing really impressive protection. So if anything, at that point, herd immunity seemed more within reach than at any other time. It seemed like, hey, we've got these amazing vaccines.

We're going to get there for sure. Right. So when did that start to change? So if you remember, the vaccines were authorized in December. And just around that time, we started to hear about more contagious versions of the virus. The variants. The variants, exactly. We started to hear about a new version of the virus that was circulating in the United Kingdom that seemed much more contagious than the version that we had been seeing so far. And that really changed the conversation, at least among scientists. And they started to say that now we're going to need a higher percentage for herd immunity.

Explain that. Why would that be? Why would the British variant change the discussion around herd immunity? So herd immunity is calculated in a formula based on the contagiousness of a virus. Very basically, when you increase the contagiousness of a virus, then herd immunity goes up. That's just the way the formula is. So now that you're looking at a more contagious version of a virus, then heart immunity goes up. That's just the way the formula is. So now that you're looking at a more contagious version of this virus, you need not 60 or 70%, but now you need at least 80%

and possibly as high as 90, maybe even 95%. Which is a very significant increase from 60 or 70% immunity in the United States. Right. So to get to that point, we would have to convince just about every American to get vaccinated.

Right. So that was the case back in December. But now, lucky for us, at this very moment, the U.S. has three vaccines that have been granted emergency authorization and are being distributed around the country, which would seem to be allowing us to potentially reach that goal. Seem to be. But the problem is that we have a very significant proportion of the population that just doesn't seem to want the vaccine. We've seen just in the

last few weeks that the rate at which we're vaccinating is falling. There are all these reports of vaccination sites that are essentially sitting empty, waiting for people to come through their doors. We're seeing states and cities get really desperate and offer all kinds of incentives just to get people to come and get vaccinated. So we should have an easy time getting to this percent, but it doesn't look like we will. How short are we falling of the level of vaccinations that would be required to reach herd immunity at this point? Well, let's just look at the level of vaccinations to begin with. According to the CDC, about 30% of the population is fully protected. And by that, I mean they've either had both doses of either the Pfizer or the Moderna vaccine, or they've had the one dose from the Johnson & Johnson. So 30% are fully protected. That's very far from where we need to be.

let's say another 30% of the population has been exposed to the virus at some point and has had some protection through natural infection, we're still only at about 60%. We're nowhere near that 90% that we need. So just to summarize, variants of the virus make herd immunity harder to achieve in the U.S. than it was when we started having this conversation last year. And we realized that the only way to achieve in the U.S. than it was when we started having this conversation last year. And we realized that the only way to achieve it is through exceptionally high levels of vaccination, which we are not doing. So that's how you get to these depressing conversations you're having

with scientists who are suddenly telling you that it looks like that herd immunity we all talked about and we all thought we could achieve is now actually not achievable. Right. And really, if I had spent some time thinking about both those things, I should have known that what I was going to hear is that herd immunity is not achievable. If any of us could do the math that these scientists do,

we should have guessed, and I should certainly have guessed. Hmm. And if what you're finding is true for the United States, where there's a lot of vaccine and a lot of places to get vaccines, is it true as well for the rest of the world that herd immunity is very unlikely to happen

in any country? Not necessarily. It's unlikely to happen in the near future, yes. But as vaccines start to become available in other places, I think they may do much better with convincing their population to get vaccinated. This is where our American exceptionalism is really coming into play.

Americans just don't like to be told what to do. But I think vaccines will be a much easier sell in places where people are used to taking vaccines and people will actually line up and want to be vaccinated. So this could end up being a uniquely American problem with unique American implications. It could, and it's very depressing. We are the country with the most vaccines at our disposal,

and yet we seem to have the highest rates of vaccine hesitancy. There are some in other countries as well, but not like in the United States. Our American exceptionalism is really going to end up being a problem if we don't make inroads into this hesitancy. And we could end up being the only country in a few years' time that still hasn't made it

anywhere close to herd immunity. And therefore, has COVID in our lives for a long time? For the foreseeable future. We'll be right back. We'll be right back. So Prabhu, what does it look like to live in a country in which there is not herd immunity? And especially a country like the United States that has started to reopen and yet is not really on its way to herd immunity? What it probably means is that we are going to hear about outbreaks of the virus in different parts of the country throughout the year.

We'll hear about outbreaks in any place that doesn't have a very high level of vaccine acceptance. Hopefully they will not be anywhere near what we saw, you know, in the months of winter when the numbers were just really horrifically high. But we will probably still hear about lots of very sick people and some people dying for many years to come. Many years to come? That's right.

The best estimate so far seems to be that we might sort of bumble along this path for the next generation or two. But at some point, all the adults will have either been vaccinated or they will have had the virus once. But that might take 20 to 40 years. So during the intervening 20 to 40 years, when we wait for that point, I wonder if you can describe the kinds of outbreaks

that we're going to be experiencing, what that's going to feel like. Is there an analogy that comes to mind? Well, think about the Orthodox Jewish population in New York and just north of the city. They've had some really bad measles outbreaks because they're not vaccinated for measles. Same with Los Angeles, where for many reasons, the vaccine acceptance is very low. And those places have seen measles outbreaks that really have flared very quickly out of control because there's very little herd immunity in those particular pockets. But those do spill out into the broader community sometimes and infect, say, babies that haven't yet been

vaccinated or some older adults who've lost immunity over time to the measles virus. That does happen sometimes. So we're talking about seeing these pockets of virus popping up all through the country and sometimes spilling over even into the neighboring communities where people did get vaccinated for the most part. And how risky will those outbreaks be for the average person who is vaccinated? Well, for the vast majority of people who are vaccinated, it probably won't be. And even if they do get infected, they may not get very sick. But there are cases that we've seen already where even people who've been vaccinated can get infected. There

was just a case in Kentucky at a nursing home where there was an unvaccinated staff member who infected 26 residents of the nursing home. And 18 of them, of that 26, had been vaccinated with both doses of the vaccine, two weeks past the second dose, which is what we're supposed to have. And still, they were infected. Some of them had symptoms, and two of them died. Wow. So there's a likelihood that you will not get as sick

if you've been vaccinated before, but it's not a full guarantee. So in a world where we have not achieved herd immunity, the world we're living in now, and it looks like we will be living in for, as you say, up to a generation, things like this will happen, where an unvaccinated person, the kind of person who's keeping us from achieving herd immunity, will infect vaccinated people, and some small percentage of them will get really sick and an even smaller percentage of them will die. That's right. And I think this is very important to emphasize also

because I've seen a lot of this sentiment of, you know, if people don't want to get vaccinated, that's on them. Why should I care? But there are a lot of people like the elderly, for example, who may not put up a very strong response even when they get vaccinated. There are so many immunocompromised people, you know, either because they had cancer or who take some kind of medication that don't really produce antibodies when they get the vaccine. And so we do have to think about all of those people as being susceptible when there's an outbreak. about all of those people as being susceptible when there's an outbreak. And there's something else we need to think about, which is that every person that the virus infects is another opportunity for it to mutate. So when you have the virus circulating in big numbers of people again, we are giving the virus so many chances to mutate into something that is more contagious or that our vaccines are not quite as effective against.

So we have to be very careful to also contain the virus and its ability to mutate. So once we as a country acknowledge that we're not on a path to herd immunity because of the variants and because of vaccine hesitancy, it brings us to this interesting juncture because we know we can't really affect the course of variants, but we can, in theory, affect the number of Americans who get vaccinated. That's where, as a country and a government, we would seem to have the most leverage, the most power to affect the course of this. So how do the people you talk to, the scientists and the public most power to affect the course of this. So how do the people

you talk to, the scientists and the public health experts, think about that and talk about that? First of all, I think there's still a lot of progress left to be made in cutting down this level of hesitancy. But if we still have a percentage of the population that just does not want a vaccine, we can still get a lot of benefit by focusing on the people who are highest at risk. It feels like the ultimate question here is just how consequential is it that we won't achieve herd immunity or that if we achieve it, it won't be for a very long time. And so we will live in a world of periodic outbreaks, a world in which COVID is still in our mostly vaccinated midst.

So how do you think about that on a scale of scary to manageable? Listen, I understand that this is a huge mental shift for people to have to give up on this idea that we were going to get to herd immunity. I went through the same thing when I started calling these experts. Can you hear me? I can hear you fine, yeah. Great. Towards the end of my reporting, after I talked to all the other experts, I called Tony Fauci. I have reporters ask me every single day, when are you going to reach herd immunity? And I asked him, you know, how worried should we be about this? And I say the same thing that the people you've been talking to. I say, wait a minute, forget this issue of herd immunity and just get as many people vaccinated as you possibly can, as quickly as you possibly can.

And what does this mean for the future of this country? You can get, you know, a certain percentage of the population vaccinated. And in fact, you don't necessarily reach the classic definition of herd immunity, but you still have a considerable amount of impact by vaccinations. What we really should care about is protecting those high-risk people, vaccinating the people who are most likely to get sick or to die. And as soon as you do that, pretty soon, sooner rather than later, you're going to start seeing the infections coming down. We can still bring down what we really worry about, which is the number of hospitalizations and deaths and the health care system just buckling under the weight of that. We can still prevent that.

So herd immunity is not an off-on switch. It's a continuum, right? And we are somewhere along that path. And the more we keep walking along there, the better our world will look, the less scary it will look. So it doesn't have to be a dire thing. We're just changing what we consider to be our goal. Thank you. All right. Take care. Well, Pramod, thank you very much. Always a pleasure. Thank you very much.

Always a pleasure. On Monday's show, we'll explore the causes and impacts of vaccine hesitancy in a single town in rural Tennessee. We'll be right back. Here's what else you need to know today. So right now I have what we think is the strongest election integrity measures in the country. I'm actually going to sign it right here. It's going to take effect. It's going to take effect. So, there you go. On Thursday, the governor of Florida, Republican Ron DeSantis,

signed into law new restrictions on voting, many of them making it harder to vote by mail. And me signing this bill here says, Florida, your vote counts. Your vote is going to be cast with integrity and transparency, and this is a great place for a democracy. Real quick question. Governor, real quick question. DeSantis said that the law was necessary to improve confidence in election security after the 2020 election. Despite DeSantis himself having previously described that election in Florida as, quote, the most transparent and efficient election anywhere in the country.

In an unusual move, DeSantis refused to allow any members of the news media, except for Fox News, to observe him signing the law. Today's episode was produced by Daniel Guimet and Sidney Harper, with help from Michael Simon-Johnson and Robert Jimison. It was edited by M.J. Davis-Lynn and Rachel Quester and engineered by Chris Wood. The Daily is produced by Lisa Tobin, Rachel Quester, Lindsay Garrison,

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