BROOKE GLADSTONE This is On the Media, I'm Brooke Gladstone. As we consider the current state of our immunity, we take a step back to 2020, when we were all abuzz with the phrase "herd immunity" and its companion "flattening the curve." We believed that with enough antibodies, however we got them, we could as a population become, quote, fully immune and stamp out the virus for good.
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NEWS REPORT Herd immunity could be our best chance of getting back to enjoying ourselves together. If enough people have the antibodies for COVID 19. The entire population can be protected. [END CLIP]
BROOKE GLADSTONE Alas, breakthrough infections and reinfections are increasingly common since the delta and now the Omicron variants have emerged. This fantasy of a clean and easy fix has been obliterated.
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NEWS REPORT As Omicron spread quickly across the globe. Some experts had hoped there could be a silver lining. That it would help finally deliver the promise of herd immunity against COVID 19. But herd immunity in which enough people become immune to a virus through vaccination or infection won't come with Omicron, experts now say. [END CLIP]
BROOKE GLADSTONE Thus herd immunity, already fraught by dint of its demeaning name alone, was abandoned. But David Robertson, a doctoral candidate in Princeton's History of Science program writing in Stat News explains that we never really understood what herd immunity meant for COVID in the first place.
DAVID ROBERTSON Early on, primarily in Britain, was where it first took off as a term. Back in mid-March of 2020 before the UK decided to lockdown, when they were basically going to do an approach that would have been voluntary, social distancing and other measures. Experts there have said that this epidemic will ultimately end with herd immunity. Whether or not to get a vaccine, the aim would therefore be to protect vulnerable people while that happened. Sometimes they gave a number. They said probably about 60% of people would need to recover. The idea was not to allow infections to happen, but to accept that they were going to happen and to therefore try and focus resources on not letting them happen among those people who would be particularly high risk.
BROOKE GLADSTONE Some people came to interpret the term as a do nothing, let it rip strategy, you wrote that would result in a huge number of avoidable deaths.
DAVID ROBERTSON Some people got fixated on the term herd and used this to suggest that it's an inappropriate term for human populations. It's important to note that herd immunity as a term was not coined to understand immunity arising from vaccination. It was coined to understand immunity arising from infections. It became much more closely linked to vaccination policy from roughly the 1970s onwards, and that's largely because of the immense success of postwar mass immunization programs against polio, measles, smallpox, which was eradicated in this period. But with these diseases, we get sterilizing immunity either from previous infection and recovery or from vaccination. And so someone can't be reinfected and can't pass the pathogen on.
BROOKE GLADSTONE One thing I learned from your piece was this phrase "elimination threshold." We seem to think, at least at the beginning, that some strategy or other would provide an elimination threshold. Generally, vaccination would get rid of this, but...
DAVID ROBERTSON that's not the case with more mutable diseases like SARS-CoV-2. I mean, we knew that because we have other coronaviruses that regularly infect us. We've studied how often they kind of regularly infect people. That should have been the go-to assumption. That whatever kind of immunity we had from prior infection, people would ultimately be infected again. But that doesn't mean that herd immunity is no longer a relevant concept.
BROOKE GLADSTONE In fact, it was applied in the case of the historic 1918 influenza with mice to figure out how many immune individuals in a population you needed in order to eliminate the disease.
DAVID ROBERTSON In 1923, British bacteriologist had different quantities of immune susceptible and infectious mice in different cages. And every day they would study the number of infections and deaths, and they would plot these on graphs, try and correlate waves of diseases like mouse typhoid with ratios of immunity and susceptibility in operations. See if they could tinker around with these ways by increasing susceptible immune and infectious mice into different isolate cages. It was really the first time to try and really understand the mechanisms of spread of an infectious disease and the way in which immunity could bring it to a halt. So it is also the origins of this idea that there may be an absolute quantity of mutations needed in a population, and that's what the threshold is that becomes more important to vaccination policy. But I think what's also important and something that we've really lost that they had in these experiments in the 1920s and 1930s, was an attention not just to the quantity of immunity in these cases, but also that they ask about. What would be the best way to distribute immunity across that population? And so when SARS-CoV-2 comes along and by March, April, we know certainly who's at most risk. I read this as really saying, if we can't stop this thing from sweeping through the population, how can we maybe try and distribute immunity, viral infection, vaccination when it comes to make sure that happens in places that will protect those people the most?
BROOKE GLADSTONE But the whole notion became something of a PR nightmare. Back in October 2020. You wrote about a trio of epidemiologists from Stanford, Oxford and Harvard who came together to voice their support for these herd immunity tactics. It was a document called the Great Barrington Declaration, drafted at the American Institute for Economic Research, a libertarian think tank based in Great Barrington, Massachusetts. They said that you couldn't really eradicate this virus and that instead of strict lockdowns, governments should just protect the most vulnerable while allowing natural infections to build up everyone else's immunity. And as you noted, this did not go over well.
DAVID ROBERTSON Well, so it was dismissed as quote unquote, fringe epidemiology by Anthony Fauci and by others. It was dismissed by other people like Dr. Tedros and W.H.O.. But in my opinion, no one really engaged with the substance of the declaration. They focused on the fact that the declaration was in some sense, anti lockdown was against severe restrictions like school closures. So that was damaging to those people who are least vulnerable to COVID 19. But really, that was an unfair characterization. The important part of that document was what was called focused protection. It was the idea that we have limited resources and we can only do things for a certain period of time. Therefore, what we need to do is use the greatest resources we can to protect those people known to be at highest risk. And so the authors elsewhere outlined four different risk groups. The first well-known risk group with elderly people in care. And so they suggested, for instance, using people who had already recovered and had some level of immunity to SARS-CoV-2 to work in close knit settings with these people to help minimize infections, to focus testing on care homes. And there were many other ideas. The main thrust of the great declaration in my mind and the great tragedy of it being dismissed, was that this idea of focus protection was thrown out the window.
BROOKE GLADSTONE I mean, it sounds wonderful to protect the vulnerable and let everyone else roam free collecting antibodies along the way. But since COVID is erratic and who is vulnerable is something that turned out to be more difficult to define than we anticipated. And the Great Barrington Declaration came out before there even was a vaccine. Didn't that make relying on natural infection even more of a bad bet?
DAVID ROBERTSON There are lots of places that didn't do severe restrictions and lockdowns. They may have had bad outcomes. There are lots of places that did very severe restrictions. Such as Peru, which had one of the worst outcomes. New York did quite severe restrictions, had very bad outcomes early on. The U.K. did a lot of restrictions, had bad outcomes. So I'm not so convinced that there's an easy, direct relationship between the severity of restrictions and the public health benefits. But putting that aside, I think that very few places didn't do restrictions, but also did what the Red Baron declaration called for, which was focus protection. It wasn't just do nothing and let the military build up in the population. The idea was to use limited resources to protect those people who are most at risk. While the inevitable happened anyway, which was that some people would continue to be infected until the epidemic went into a downturn. There are places that didn't do severe restrictions, perhaps, but they didn't, for instance, target testing and isolation methods of nursing homes. There wasn't even a conversation about doing that.
BROOKE GLADSTONE And when it comes to the disability community that feared being stigmatized and isolated even more, if they were the only ones who had to go behind closed doors. Take a family where a child has asthma. The child prior to the COVID 19 epidemic would go to school with all the other kids. If we used the Great Barrington Declaration approach, perhaps kids without asthma would go about their lives with limited restrictions. But those kids with asthma would have to stay home. Whereas if everybody were following extreme restrictions, then they wouldn't be stigmatized. That's the argument.
DAVID ROBERTSON It's not just children with asthma and children in general, incredibly low risk. But I think the main point stands that if our resources are focused on shutting down schools and setting up at home education through Zoom and other mechanisms like that, well then how many resources do you really have to give to that one or two students at the school who actually are in the risk category. You're just basically throwing them in the same category as everyone else and not providing them with special resources. The results are coming out now. I mean, at home, education was an abysmal failure for many children, particularly poorer children, and particularly for children at higher risk.
BROOKE GLADSTONE And so on. The matter of the phrase herd immunity. We should have replaced Hird with a collective and the word immunity with protection or resistance. Tossing out both words.
DAVID ROBERTSON Personally, I don't have such a problem with the term herd. I think it does its job of identifying the idea of a collective. I understand why other people may not like it.
BROOKE GLADSTONE But immunity that you have a problem with. The policy prescriptions would have made more sense when people understood that they weren't promising a cure but protection for the greatest number of people.
DAVID ROBERTSON For me, the crux of this term and the reason we failed to understand it was precisely because it's this question of immunity, where immunity meets me and society, and it's navigating how my immunity works and fits in with those around me, how infection works in kitchen windows around me. And COVID 19 came at a time of immense social atomization. And so, perhaps predictably, our response to that question was to see it as a very individualistic question about personal immunity. Personal protection.
BROOKE GLADSTONE David, thank you very much.
DAVID ROBERTSON Thanks for having me.
BROOKE GLADSTONE David Robertson is a doctoral candidate in Princeton University's History of Science program.
