President Trump has long seemed fascinated with the idea that herd immunity could provide an easy end to the coronavirus pandemic, even before his own diagnosis with covid-19 and his blithe declaration after he checked himself out of the hospital that no one should be afraid of getting it. “With time, it goes away,” he told an ABC News town hall last month. “And you’ll develop — you’ll develop herd — like a herd mentality. It’s going to be — it’s going to be herd-developed, and that’s going to happen. That will all happen.” The neuroradiologist he brought in to advise on the pandemic response over the summer, Scott Atlas, has argued that rising case counts will bring the nation to herd immunity faster.

Now the White House has turned this half-baked idea into an official strategy, calling it “focused protection.” In this approach, the virus would be allowed to spread among young, healthy people with little attempt to slow it down, while officials try to keep older, more vulnerable Americans from contracting it. In the modern era, herd immunity is best achieved by vaccination, when enough people acquire immunity to an infection through a shot in the arm to protect the whole community. That’s our goal every flu season; it’s the reason we vaccinate infants against dreaded childhood diseases. But now, the official policy of the Trump administration will be to try to speed up the arrival of herd immunity to the novel coronavirus by letting the virus infect people faster. Without a vaccine, though, this strategy risks the deaths of millions of Americans.

Proponents of herd immunity with “focused protection” generally oppose mask mandates, contact tracing and other measures to slow the spread of the virus because they imagine that infection can be confined to the “low risk” population and want to hasten infection in that group.

After falsely promising that the epidemic would go away “like a miracle” when the weather turned warm, the White House has now found support for its new cold-weather line of wishful thinking in the so-called “Great Barrington Declaration,” a document published last week at a ceremony at a libertarian think tank by three scientists whose views diverge sharply from those of most infectious-disease epidemiologists. On Tuesday night, a White House official speaking on the condition of anonymity told reporters that the plan “is endorsing what the president’s strategy has been for months.”

Supporters of this view are half right: We must indeed do all in our power to protect the vulnerable. More resources are desperately needed to keep nursing homes safe, including considerably increased testing capacity and personal protective equipment, better sick leave policies for their staff, and smarter ways to deploy staff so that those who may already be immune due to prior infection can interact with the highest-risk residents. More broadly, this pandemic disproportionately impacts racial and ethnic minorities, so “the most vulnerable” actually include the poor, essential workers and those who society already routinely fails to protect.

As we and many others work hard to hone strategies to protect all these populations, the administration has failed to support, and often hampered, such efforts to shield those at highest risk. For example, Trump forced meatpacking plants to reopen in April without mandatory protections in place; these venues were deemed essential but were hot spots for transmission and disproportionately employ Latino and African American workers.

Unfortunately, no one has so far devised an approach to protecting the vulnerable that really works, especially when the infection is raging in society at large. Surely we should do all we can to change that, and surely we all want to get back to our pre-covid-19 lives.

Yet until we have a proven means to protect those most at risk and put those safeguards in place, letting up on control and plunging ahead in pursuit of herd immunity via massive infection rates amounts to unilateral disarmament. Scientists and clinicians in and out of government have been working hard to protect these groups, with little or modest success, for most of the year, while also attempting to minimize the threat that community transmission poses to them and to all of us — a belt-and-suspenders approach. Letting the virus tear out of control in the population at large before we really know how to protect the vulnerable is like ripping off our suspenders before we have the belt on. Just look at Sweden, the poster country for the “age-targeted” approach: Even the architects of that strategy admit they failed their nursing homes.

Even if we had more faith that we could protect those at greatest risk, though, there are still more fundamental reasons to resist the notion of dropping our guard. That strategy rests on the notion that the virus is harmless to most people and risky only for defined groups; that we will get to herd immunity sooner or later, so we may as well do it sooner; and that if we just tell people to go back to normal life, the world as we knew it in 2019 will return.

These are all false hopes.

Covid-19 is unquestionably worse for someone who is male, older, sicker or lacks access to health care. But it’s dangerous for all of us. It is true that, compared with older demographics, the young and healthy fare well. But the Centers for Disease Control and Prevention estimates that nearly 50 percent of Americans live with underlying conditions that predispose them to serious outcomes from covid-19. So far, 42,000 Americans under 65 have died from the disease — more than four times as many as typically die in that age group from seasonal flu — and we’ve only had eight months or so of intense covid-19 activity, so the numbers will keep growing. If we let the virus spread uncontrolled in the younger population, we will indeed build up some herd immunity that will probably reduce further spread — for a while. But coronavirus immunity is notoriously short-lived and partial: Other coronaviruses are called “seasonal” because, like the flu, they circulate every year. The result of letting the infection go in the general population will, in all likelihood, be a persistent problem, not a nightmare followed by a blissful awakening.

CDC Director Robert Redfield told Congress in late September that over 90 percent of the U.S. population remains susceptible to this coronavirus, citing published data. Recently, proponents of herd immunity have pointed to the existence of T cell immunity in some of the unexposed population to suggest a far lower share of the public might truly be susceptible, but this misunderstands how T cell immunity works and how epidemiological models are fit to data. Whatever T cells are doing to protect us is already “baked in” to the estimates that we will need half the population or more to be immune before transmission relents.

Returning to pre-pandemic levels of activity risks a return to levels of transmission like those we saw in the hardest-hit places in the early spring, such as New York, New Orleans and Detroit, with hospitals overwhelmed and ICU beds in short supply. All the sacrifices of the last months will have been largely wasted, delaying but not fundamentally changing the devastation of an unmitigated pandemic. Among other consequences, this will mean that the return to “normalcy” hoped for by herd-immunity proponents will not occur, as fear of exposure would keep people home even if there were no rules requiring it. Indeed, economists report that states that ended their spring lockdowns early have had the worst, not the best, economic outcomes, resulting from rampant viral spread.

“Flatten the curve” was a good idea when the world first heard the concept in March, and it still is. Even if we assume herd immunity will come sooner or later through the natural spread of the infection, we should prefer to delay it. A flatter curve, with more infections delayed, means a health-care system better able to cope with the cases it does have. Treatments are getting better, and there are indications that more people who would have died of covid-19 earlier in the outbreak are surviving. Further, data suggest that only two-thirds of the 225,000 excess deaths from March to August were covid-related; an overwhelmed health-care system means there is little reserve to care for all the other diseases hospitals were created to treat. And there is every reason to expect medical care for this new disease to be better in three or six months than it is now. Last and most important, vaccines are being tested that might just protect us if we can stay uninfected long enough to get our immunity that way.

We can find common ground with the proponents of focused protection on the need to find more and better ways to shield the vulnerable until then, and to be smart about what restrictions we use to reduce viral spread. We also agree that control measures are taking a toll on everyone, particularly those who are economically disadvantaged. But until we have a way to reduce the devastation of this virus, through treatments or vaccines, we have a moral obligation to suppress its spread while enhancing economic, educational and medical support for those whose lives are most disrupted by our control measures.

The question of whether to, as Trump put it earlier this year, “go herd” is not a scientific debate. There is no scientific data showing that a country like the United States can protect those at greatest risk while letting the virus spread uncontrolled. The debate is over how to live while we wait for a vaccine good enough to protect the vulnerable and provide herd immunity.

The Great Barrington approach and its champions advocate a strategy that abdicates our responsibility by letting up on control of the virus with no proven means to protect the vulnerable. This will cost lives and, if the summer is any indication, further damage the economy while pursuing a goal of herd immunity that may prove only temporary even if reached. We must keep up the efforts on both fronts — supporting those at greatest risk while limiting spread of the virus to prevent unnecessary illness and deaths.

correction

An earlier version of this story gave an incorrectly low figure for how many more young people have died from covid-19 than typically do from the flu. Covid-19 has killed more than four times as many young people as the flu usually does, not less than twice as many.

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