Herd immunity is achieved when a population becomes largely immune to infectious disease through vaccination or through infection.
As it pertains to the COVID-19 pandemic, experts say that achieving herd immunity by letting the virus spread unchecked through the population is neither ethical nor realistic.
“I think it is absolutely indefensible to just allow the disease to spread without any sort of intervention in order to reach herd immunity,” Johan Bester, PhD, director of bioethics and assistant professor of family medicine at University of Nevada Las Vegas School of Medicine, tells Verywell. “That is an unethical approach given that there are other ways that are more effective and protect the well-being of people.”
Infection-Induced Herd Immunity
The United States has more than 330 million people. To achieve the herd immunity threshold of 60% necessary to curb outbreaks, that means that 198 million people would have to contract SARS-CoV-2 (the infection that causes COVID-19), according to a Yale University study published in JAMA.
According to the Johns Hopkins Coronavirus Resource Center, as of the end of October 2020, approximately 9 million Americans have had confirmed cases of COVID-19—about 3% of the U.S. population.
“Imagine that 60% of the American population has to get sick, or in any given state 60% of the population has to get sick,” Bester says. “We’re talking about astronomical figures of death and disease and long-term complications and all those bad outcomes we don’t want in order to establish herd immunity.”
“As a physician, I could never endorse that,” Mark Schleiss, MD, an infectious disease expert, molecular virologist, and a professor in the Department of Pediatrics at the University of Minnesota, tells Verywell. “To me, that is completely unthinkable.”
An Unrealistic Concept
According to the Yale study, while herd immunity is considered a successful strategy for immunization programs, we don’t have an example of a successful wide-scale strategy that has purposely used infection to achieve community protection.
“There have been some studies that have come out that showed that people’s measurable antibodies drop month by month after they’ve recovered from COVID,” says Bester. “And there have been some reports of potential reinfections. And we have the example of other coronavirus diseases besides COVID that keep coming back and that people can get more than once.”
The Death Toll
Although it does not provide exact numbers, the Yale study points to the substantial mortality that would result from intentionally trying to achieve herd immunity through infection of a virus that does not yet have a safe and effective vaccine.
A death toll is hard to predict if the virus were to spread unchecked in the United States. “All I can do is look at the history of infections that behave similarly with similar death rates," Schleiss says. The 1918 influenza pandemic, for example, killed about 675,000 Americans, according to estimates from the Centers for Disease Control and Prevention (CDC).
“It might be dangerous to compare it to the total number of deaths in the United States from influenza in 1918,” Schleiss says. “We’ve mitigated this more, and yet we have so, so many deaths already.” As of the end of October 2020, more than 229,000 Americans have died from COVID-19.
That is the death toll when just 3% of the nation has had a confirmed infection—a long way from the herd immunity threshold.
Estimates place the SARS-CoV-2 herd immunity threshold at about 60%, but it could be higher.
The threshold varies by disease and is based on how many people get infected when one person has the infection.
“We’re not sure what that number is,” says Bester. “But at least 60% to 70% will need to be immune to have any sort of herd immunity response. The point is you still need a whole lot of people to get [the] disease to get herd immunity.”
The CDC says that older adults and people with certain medical conditions are at a higher risk for severe illness from COVID-19. Severe illness also puts people at a higher risk of death. The Kaiser Family Foundation estimates that 92.6 million people fall into this high-risk category.
“You can see that we are talking about an astronomical death toll,” Bester says. “And that should be unacceptable by any measure.”
Post-Virus Complications
Loss of life is not the only consequence of a pandemic—and it’s not the only impact of COVID-19. “Death is one problem,” Bester says. “But the other is that people who don’t die might have serious outcomes that they live with for the rest of their life.”
Letting the virus run unchecked could lead to more complications. Individuals who have developed long-term complications or lasting symptoms from COVID-19 have been dubbed “long-haulers.” “We don’t know how big that group is going to be,” Schleiss says, “but I think the long-term, sequela of that is going to be a big, big burden on society.”
Sequelae are conditions or injuries that develop after someone has had a disease. Researchers are still learning about the complications that can arise from COVID-19, but some trends are emerging. “Permanent damage to the brain, the heart, the kidneys—these are all really, really worrisome issues,” Schleiss says.
Healthcare System Burden
Acute illness from COVID-19 as well as the long-term complications in those who have recovered can overburden community healthcare systems quickly. “Our healthcare system is built with a specific capacity in mind,” Bester says. “And it’s hard to just ramp up capacity.”
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Other health issues and emergencies don’t fall to the wayside just because society is in the midst of a pandemic. The other patients that we usually see—people in car accidents, people with heart attacks, people with cancer, and so on—have to compete with COVID patients for the same resources,” Bester says.
Chasing the goal of achieving herd immunity through infection would also make healthcare resources scarce, making it more likely that difficult decisions would have to be made regarding treatment. “Somebody would have to decide who we let go in terms of palliative care,” Schleiss says as an example. “And that’s probably going to have to be the politicians because that’s just not compatible with what we do as doctors.”
Other Country’s Strategies
In the early weeks of the COVID-19 pandemic, Sweden did not mandate lockdowns. The country has since made headlines for being a nation attempting to achieve herd immunity through infection.
The Yale study found that while the country has taken some measures to mitigate virus spread, Sweden is far from achieving herd immunity through infection. In fact, it’s experiencing fallout from lax strategies.
“I think the Swedish COVID-19 response has quite frankly been unsuccessful,” Schleiss says. “And it should not be held up as a model for the rest of the world. The per capita death rate in Sweden from COVID-19 is in the top 10 of all global death rates.”
Bester and Schleiss suggest looking to New Zealand as a nation that is doing an exemplary job of controlling COVID-19. “New Zealand very early on came together as a society with leadership from the government saying, ‘We are in this together and we are going to stand together,’” Bester says.
New Zealand has mostly stopped the spread of COVID-19, with the exception of a few small outbreaks. The nation has worked to get outbreaks under control through rigorous testing and localized quarantines when needed.
“I would love to see us be able to do something like that in the USA,” Bester says. “Where we pull together and say, ‘We’re going to beat this thing for each other and do what needs to be done.’”
The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.
While we wait or vaccines to help mitigate virus spread, the best ways to protect yourself and others from infection are wearing a face mask, practicing proper hand hygiene, and socially distancing.
