Don’t Wait for Herd Immunity

An illustration of green clusters on a red background
Adam Maida / The Atlantic

With 200 million doses administered, America’s vaccine-distribution program has been remarkably successful, but now it is hitting a wall. The rate of COVID-19 vaccinations is dropping; the percentage of people not returning for their second shot has risen. Fortunately, the number of Americans who are resolutely anti-vaccine remains small, a stubborn 13 percent, so finding ways to win over the rest remains an urgent task.

The underlying reality ought to be discussed more forthrightly. The United States may not reach the point at which enough people have become immune—by either getting vaccinated or having overcome a previous infection—and the coronavirus cannot spread in the population. This has been evident for some time. “We likely won’t cross the threshold of herd immunity,” Sarah Zhang wrote in The Atlantic in February. Yet the elusive possibility of herd immunity continues to shape Americans’ expectations. Getting there would simplify many questions about lifting mask orders and business restrictions, but mayors and governors who are reluctant to take such steps without a green light from scientists could be waiting for a long time.

The idea that a pandemic ends once the population reaches herd immunity has historical precedent. Last year, that notion took a macabre turn, as some within the Trump administration proposed letting natural infections rip through the population. The more humane route to herd immunity, embraced by the nation’s most prominent infectious-disease experts, was for Americans to listen to scientists and get a couple of shots. “By the time we get to the end of the summer, i.e., the third quarter,” Anthony Fauci said in December, “we may actually have enough herd immunity protecting our society that as we get to the end of 2021, we can approach very much some degree of normality that is close to where we were before.”

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But to stake fundamental decisions about how society will operate upon a deceptively simple scientific standard is to wish away considerable ambiguity of the data. One reason herd immunity appears so elusive is that no one has determined what the right threshold is. The CDC website simply says that “experts don’t yet know” when herd immunity will set in. Late last year, Fauci indicated that herd immunity would arrive when 75 to 85 percent of the population had been infected or vaccinated. The difference between Fauci’s lower and higher number is about 33 million people, and even the lower one can’t possibly be achieved without vaccinating Americans under the age of 18. More recently, he has described herd immunity as a “moving target.” The World Health Organization puts the number at 60 to 70 percent. In Israel, 60 percent of the population had received at least one dose of a vaccine by April 19. The country recorded just 151 new cases that day, down from 8,000 in early January. Its experience suggests that the U.S. could soon achieve the same outcome—a major drop in cases without fully stamping out the virus—as the number of vaccinated Americans gradually increases.

I am a former homeland-security and disaster-preparedness official. For the past year, I have advised mayors, governors, and private-sector leaders on COVID-19 response and vaccination plans. Although I am not a scientist, I believe strongly in making decisions grounded in science. The information that doctors and researchers provide is like other forms of good intelligence: based on data and other provable facts, but incomplete or inconclusive at times, and subject to revision. To imply that science can make politicians’ decisions for them puts a lot of pressure on scientists and discards other forms of expertise—including skill at communicating with the public and mastery of supply-chain logistics—that are essential to guiding a large, diverse society to the other side of a crisis.

Whether the minimal risk of catching COVID-19 from a passing jogger on the sidewalk warrants making everyone wear a mask outdoors is not a purely scientific question. Likewise, science informed the decision to resume the use of the Johnson & Johnson vaccine despite a small number of serious side effects, but this too was a value judgment: Should Americans tolerate tiny risks in the name of getting back to normal? Especially if herd immunity is an unlikely goal, Americans should measure success in terms not of risk elimination but of risk minimization, and authorities should embrace the latter goal more explicitly.

We have plenty of reasons to worry about the continuing pandemic: the variants, runaway viral spread in India and Brazil, differences in vaccination rates that mirror racial and political divides. But cautionary public-health guidance risks losing its impact if it fails to acknowledge what the American public surely can see: We are winning the war against COVID-19 in the United States, and we can adapt better than the virus can. The tools with which Americans have become familiar in the past year—testing, masks, targeted business closures, the selective protection of the most vulnerable groups, public-education campaigns to promote the new vaccines—can be deployed as needed. When conditions improve, government guidelines that have kept schools closed, discouraged travel, and imposed far-reaching mask requirements need to be updated. The CDC took a step in this direction this week, lifting a recommendation that masks be worn outdoors at all times.

Homeland-security policy offers some useful lessons for how daily life might further evolve in the coming months. Instead of imposing requirements that restrict everyone’s activities equally, governments and private entities may rely on drawing sharper distinctions between “unburdened” and “burdened” classes. TSA PreCheck is a perfect example: If people take a few affirmative steps—providing the government with some background information and submitting to a security screening—they avoid certain hassles at airport checkpoints. People are free to refuse, but they’ll have to wait in line and be ready to take off their belt and shoes.

In a similar spirit, the European Union will open travel to U.S. citizens, but only those who have been vaccinated; some major sports teams are reserving spaces for vaccinated fans only; many colleges and universities are requiring vaccinations for admission; major employers are likely going to do the same. People who refuse shots will be subject to sanction from private enterprises that, unlike certain elected officials, feel no obligation to indulge vaccine deniers. Vaccine hesitancy might not be evenly distributed across the country; the resumption of normal activities in places with high vaccination rates and continuing COVID-19 outbreaks in areas with low ones could change minds over time.

Will these steps eventually get the United States, or at least large parts of it, to the point where the virus cannot spread? If we’re lucky. But even if not, we are moving incrementally closer to victory. It will probably come not as an official announcement that herd immunity has been achieved, but when vaccinated Americans begin to feel comfortable with a hug, a coffee date, or even a late-night dance party that might have seemed reckless just days or weeks before.