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Herd Immunity Is Not a Strategy

Source: The Atlantic by James Hamblin

What the term actually means, and what it doesn’t

One of the pandemic’s most insidious misconceptions is getting closer to explicit national policy. On Monday, The Washington Post reported that a top Trump medical adviser, Scott Atlas, has been “urging the White House to embrace a controversial ‘herd immunity’ strategy.” Atlas subsequently denied the report, though during his time as a Fox News commentator he consistently argued in favor of fringe approaches that go hand in hand with the idea: namely that city and state shutdowns are deadlier than the coronavirus itself.

The idea of abandoning preventive measures and letting the virus infect people has already gotten traction in the administration. Just last week, Atlas moved to ease up on the most important strategy to fight the virus—widespread testing—by telling the Centers for Disease Control and Prevention to change its guidelines to advise against testing asymptomatic people. On Monday night, the president referenced the concept in an appearance on Fox News, explaining, “Once you get to a certain number—we use the word herd—once you get to a certain number, it’s going to go away.”

But “herd-immunity strategy” is a contradiction in terms, in that herd immunity is the absence of a strategy. Herd immunity is an important public-health concept, developed and used to guide vaccination policy. It involves a calculation of the percentage of people in a population who would need to achieve immunity in order to prevent an outbreak. The same concept offers little such guidance during an ongoing pandemic without a vaccine. If it were a military strategy, it would mean letting the enemy tear through you until they stop because there’s no one left to attack.

We may hear even more talk of herd immunity as the election nears, since Trump has an incentive to claim that the pandemic is almost over even if it’s not. So now is a good time to revisit exactly what herd immunity means and, perhaps more important, what it doesn’t. I talked with Howard Forman, a health-policy professor at Yale University who has followed the data on how “herd-immunity strategies” have gone in various countries. The full conversation appears on the latest episode of Social Distance, which I host with Katherine Wells, The Atlantic’s executive producer of podcasts. This transcript has been edited for length and clarity.

James Hamblin: What do you make of news about a “herd-immunity strategy” reportedly being discussed in the White House?

Howard Forman: This is one of these topics that very few people understand. [People] use the term herd immunity flippantly. Some talk about it as a policy prescription without knowing what it even means. And I think that there’s a lot of nuance here. In a situation like this, where we’ve already lost 180,000 lives, we shouldn’t be flippant about things. We should be thinking about how to avoid as much death as possible, and resume life as well as possible.

Whenever people talk about herd immunity, whenever they talk about “ripping the Band-Aid off” or any of those things, it is an absolutely dangerous idea. Now, I think there are lessons to be learned from Sweden, and no one should be flippant about saying Sweden was horrific or the worst thing that could have happened. But Sweden ultimately did not pursue the policy that we seem to be pursuing right now.

Katherine Wells: I thought they did?

Hamblin: Sweden became this reportedly textbook case of using a herd-immunity approach, or at least, they initially said they were going to.

Forman: It started off with Sweden and the United Kingdom talking about pursuing herd immunity. Then England got cold feet and Sweden supposedly proceeded with this, but they didn’t. Sweden did a lot of things to curtail the spread. What people seem to not understand is that we do things in our country, even in some areas that are “still shut down” that would not be tolerated in Sweden. They still have a ban on gatherings of 50 people or more.

Wells: Oh! I feel like the picture of Sweden I have in my mind is everyone outside without masks, enjoying the summer, all together.

Forman: For the most part, they are without masks. But they still have a complete ban on visiting retirement homes. They still have a ban on public gatherings of 50 people. Gatherings for religious practice? Banned. Theatrical and cinema performances? Banned. Concerts? Banned. And this is what bothers me. Our president did a rally in Tulsa. That would have been banned in Sweden.

Hamblin: So if anything, we’re the country that’s maybe closest to this herd-immunity approach? I don’t even want to use that term because we’re doing a lot as well. But no one is honestly just letting the thing run wild, as the idea might suggest.

Forman: That’s absolutely correct. If you have a good understanding of herd immunity, then you know that it means that if we achieve a certain percent of immunity in the population then you cannot get an epidemic outbreak in that community. You can still get spread. You could still have a person come to our country with measles and go into a classroom and somebody will get measles from that person, but you will not have a measles outbreak because there are sufficient numbers of people that are immune to measles that in the process of trying to spread, the virus will extinguish itself. You might get two or three people infected, but it will never take off again. That’s herd immunity. That requires individuals to be truly immune to the virus, which means that the virus not only doesn’t affect you and cause you to get sick, but you actually can’t get infected. You can’t spread the virus if somebody comes in proximity to you.

Wells: And we should mention, just always keeping in mind that herd immunity, while maybe a relief now, would have come at the cost of many lives.

Forman: At the cost of many lives, and potentially, morbidity that we don’t know about yet. I say this with a lot of caution, but we have no idea whether having had this infection means that, 10 years from now, you have an elevated risk of lymphoma. There’s not any indication that it would, but we just don’t know. We know that hepatitis C leads to liver cancer. We know that human papillomavirus leads to cervical cancer. We know that HIV leads to certain cancers. I don’t want people to panic over that possibility, because I think that’s unnecessary, but just to make the point that we don’t know. So even if you thought you could get to a vaccination-equivalent immunity through infection, you still run risks beyond the immediate mortality and the immediate morbidity.

Hamblin: Right—there are things we’re not seeing that we need to consider. And so, without suggesting specifically that this virus is causing cancer, we have no idea what the long-term effects will turn out to be, and so we don’t want to mess around with infecting anyone who doesn’t need to be infected.

Forman: Right. And by the way, there’s never been a real case of herd immunity through infection.

Wells: For any disease ever?

Forman: Correct. In fact, the term itself didn’t arise until just a few decades ago, when we had vaccination programs. There are cases where, as large waves of infection passed through communities, you had lower levels of outbreak in most years, and then you would have epidemic outbreaks other years. That probably is the closest thing, but that’s not herd immunity. You’re still having outbreaks all the time. You’re just having bigger waves and smaller waves.

Wells: The term herd-immunity strategy makes even less sense to me than it did before.

Forman: We know how much testing alone could do to help us here. Combine massive testing with things like masking and social distancing, and then you have to ask yourself: Why would you allow people to just die in such large numbers when you have these alternatives that are readily available to us? And that, quite frankly, could allow us to get much closer to a normal life than we are right now.

Wells: Well, what’s the answer?

Forman: Honestly, I am at a loss. I’m hoping, by the end of November, the entrepreneurs who have been developing these cheap tests are going to allow us to test at such a massive scale at such a low cost that we’ll be able to substantially impact this in a way that we haven’t so far. But I’m also 100 percent convinced that if our federal government had thought about this back in February and March and decided that they were going to commit even one-tenth of the amount of money that they have committed to a vaccine to a cheap testing initiative, that we would have already saved tens of thousands of lives and certainly would have saved tens of thousands more going forward.

I co-wrote an op-ed two months ago where we said that testing is the vaccine. And at that time, I was quarreling about whether we should say $10 or $20 per test as being achievable. Now we’re talking about $1 to $5 for these tests. This is the way out until we have a vaccine.

JAMES HAMBLIN, M.D., is a staff writer at The Atlantic. He is also a lecturer at Yale School of Public Health, co-host of Social Distance, and author of Clean: The New Science of Skin.