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.”