Breaking down the effectiveness of herd immunity for Covid-19

Howard Forman - Yale School of Public Health Professor joins Yahoo Finance’s On The Move panel to break down why herd immunity is an important defense against fighting off Covid-19 cases.

Video Transcript

ADAM SHAPIRO: Welcome back to "On the Move." A lot of us talking about COVID-19, the pandemic and the efforts to perhaps get a vaccine, perhaps expose us to what some people call herd immunity. There is a new study that was published by the "Journal of the American Medical Association," which talks about herd immunity, in which they said it's an important defense against outbreaks and has shown success in regions with satisfactory vaccination rates.

Let's break this down to understand what it means. We've got Anjalee Khemlani joining us, our health correspondent, but also Dr. Howard Forman, Yale School of Public Health Professor, joining us from New Haven, Connecticut. And Dr. Forman, I think you need to unmute, but I am curious if you've had a chance to look at this study, what does that mean? I realize we don't have a vaccine yet, but in the context of herd immunity, what does it mean?

HOWARD FORMAN: Well, so my colleagues and I basically summarize the current literature on herd immunity at this time to give people a scientific foundation for this topic. The issues around herd immunity have existed really for a few hundred years. We started using the term herd immunity maybe about 60 years ago, but the bottom line is it works, herd immunity occurs when you vaccinate a large swath of the population sufficient so that individuals that are protected by vaccination may actually protect those who are not vaccinated. And once you get to a certain threshold, you no longer can have outbreaks in that community, in that city, in that country if you have satisfactory vaccination levels.

ANJALEE KHEMLANI: Dr. Forman, it seems like that's kind of how the flu vaccine concept works, and if lockdowns are one extreme, then herd immunity at large without a vaccine is another. Why are we even having this conversation about herd immunity right now, and how does it play a role in the coronavirus pandemic?

HOWARD FORMAN: So if somebody told me today that there would be no more therapeutics, no vaccine ever developed, coronavirus is here forever, and we can't do anything about it, then we would have to just figure out how we get the entire population over time through this period without killing off as many people as possible. And then those individuals who talk about herd immunity might have a point that we have to figure out how do we negotiate our way to that point.

What we know from so many other diseases, and we know pretty much at this point because of Phase I and Phase II trials, that vaccines are going to be very helpful, that many of the therapeutics that are coming online and that will be eligible for emergency use authorization in the next few weeks or months will be helpful. And so the goal now is how do you minimize deaths? How do you keep the economy going, get us restarted, allow people to live as close to a normal life as possible, but not have a million more deaths or even more than that prematurely in a time when we're on the cusp of actually being able to do something meaningful.

JULIE HYMAN: Dr. Forman, it's Julie here. It's good to see you. If you look back over history and the history of diseases and different types of infections, has there been a prominent example that we can look to where there was just herd immunity? I'm just curious for comparison sake.

HOWARD FORMAN: So number one, getting to herd immunity via infection accidentally may have happened, and it certainly happens in a very, very short period of time in some communities where we've had massive outbreaks over the centuries. But then immediately, you have more and more, you know, susceptibles introduced into the population. Those people then have outbreaks. So you're never able to sustain it without a vaccination program. That's really what we call endemic spread where you just continue to have more and more cases occurring. There was one good anecdote that's been written up in a community in Brazil where Zika might have reached a herd immunity. We have never in the history of mankind attempted intentionally to get to herd immunity.

ANJALEE KHEMLANI: Dr. Forman, is this conversation more political than anything right now, or is there more scientific validity to it in the context of what we're facing right now?

HOWARD FORMAN: I really don't think it's purely political. I think that people are misinformed, and they don't understand quite what they're saying. It may be that some people in ivory towers don't understand that it's impossible to protect elderly and vulnerable people who live in multi-generational homes. It's impossible to protect the 65-year-old man who drives a bus or the 65-year-old woman who is a school aide who must work, who must get to work, who must do things in person and protect them from being infected.

So there's this fantasy that somehow we can take all of these vulnerable people, put them aside, let everybody else get infected, and somehow you're going to get through this. That's just not feasible. We've proven it many times. We've watched Arizona, which had a lot of warning before the wave hit them, and we watched them have a very, very high fatality rate for a late state, and we're just going to see more deaths if we don't acknowledge the challenge that is in front of us.