With time and effort, we can build enough protection to blunt surges—but herd immunity remains out of reach.
I, as far as I can tell, have not yet been infected by the virus that causes COVID-19. Which, by official counts, makes me an oddball among Americans.
Granted, I could be wrong. I’ve never had a known exposure or symptoms, but contact tracing in the United States is crummy and plenty of infections are silent. I’ve taken many coronavirus tests, but not that many coronavirus tests, and it’s always possible that some of their results missed the mark.
If I am correct, though, then I’m in the rapidly dwindling fraction of Americans who are still coronavirus-naive. Roughly 60 percent of people in the U.S. have caught SARS-CoV-2, according to the latest CDC estimates, which go through February of this year. And that’s very possibly a serious underestimate. The Institute for Health Metrics and Evaluation, a global health-research center at the University of Washington, puts the tally higher, at 76 percent, as of the beginning of April. And Virginia Pitzer, an epidemiologist at Yale’s School of Public Health, who’s been modeling infections and vaccinations among Americans, told me the true number might even exceed 80 percent. No matter how you calculate it, though, the proportion of Americans who have been infected dwarfs the fraction who are up-to-date on their vaccines.
Just months ago, when most of the Omicron subvariants bopping around today were but a twinkle in the coronavirus’s eye, the people who’d been infected were still the unusual ones. Now that the pandemic script has flipped, it’d be easy to assume that all those infections have raised a bulwark against future surges—and that everything from here on out could be just fine. Perhaps a shred of that feels fair. Population-level protection against COVID probably is around an all-time high in the U.S., which may be why cases and hospitalizations aren’t rising as much as they could be right now: A smaller proportion of cases are turning very severe. Last week, Anthony Fauci, President Joe Biden’s chief medical adviser, told several news outlets that America had exited “the full-blown explosive pandemic phase,” and was transitioning toward a “more controlled” chapter of the crisis. But if that pivot sounds nice and neat and tidy, it shouldn’t. Cases are still rising, to levels likely undercounted, and are still meeting numbers that the nation hit during the early parts of last summer’s devastating Delta surge. Other countries are also battling gargantuan swells in cases, and new branches of Omicron’s lineage are circumventing the defenses left behind by the last. The pandemic is very much gunning.
Not so long ago, the world was clinging to the hope of herd immunity—to the notion that the population would eventually reach some communal level of protection sufficient to quash the outbreak for good. Maybe, experts posited many months back, once 60 to 90 percent of people had been infected or vaccinated or both, the virus would run out of viable hosts, and simply fizzle out. Now it’s clear that “that’s too simplistic,” says Sarah Cobey, an infectious-disease modeler at the University of Chicago. Immunity against the most serious forms of COVID has decent staying power, especially if laid down by vaccines. But our defensive shields aren’t strong or durable enough to block transmission long-term; the virus keeps finding the holes in our blockades.
That doesn’t make the protection we do have useless. The types of immunity more relevant to the current pandemic era blunt the frequency and severity of future waves, rather than obliterate them. If classic herd immunity was a silencer, then we’ve had to trade it in for herd immunity lite—a muffler, whose effects accumulate gradually, and can still strengthen with effort and time. There is no pandemic off switch. So we must instead work to maintain incremental gains: In this universe, 60 percent of people infected is mostly meaningful in that 60 is higher than 50, and 40, and anything below. It might translate into some level of heightened population resilience, but it is not a guarantee that the virus’s threat is gone.
On our messy pandemic playing field—where immunity against infection can accumulate, then wane, and transmission can be tamped down, but not totally blocked—no clear line will demarcate a post-crisis phase, says Maia Majumder, an infectious-disease modeler at Harvard Medical School and Boston Children’s Hospital.
Sixty percent infected—if that’s even accurate—actually isn’t the most relevant metric when it comes to forecasting how rough the road ahead might be. Vaccinations, too, can confer protection. And the fraction of Americans who have been infected or vaccinated is probably above 90 percent. But because immunity against infection and transmission ebbs over time, more than 90 percent exposed doesn’t translate to more than 90 percent “protected” against another viral encounter. There’s quite a “mosaic of immunity,” says Deepta Bhattacharya, an immunologist at the University of Arizona, with plenty of vulnerable cracks and crevices into which the coronavirus will still seep. Some people who have banked multiple and recent exposures—three shots and an Omicron infection, say—are quite far along the spectrum of immune protection. Others very much aren’t, because they still have no experience with the virus or vaccines at all, or have logged those encounters so far in their past that they’re likely quite easy to infect or reinfect. And for some people the safeguards of shots struggle to properly take, or fade faster because of age or underlying health conditions. To make matters more complex still, no one knows exactly where they fall along the spectrum of protection; many people can’t even say for sure whether they’ve had the virus or not, given how disastrous America’s testing infrastructure has been, and how tough it can be to detect virus-elicited antibodies in blood. “We’re in this position where we have a poor understanding of how different levels of immunity map to reductions in infectiousness,” Cobey told me.
What’s far more clear, though, is this. Across communities at the local, state, and national level, protection is absolutely not uniform. Which means Americans are trudging along a pandemic path that often meanders—and sometimes doubles back. With protection against serious disease and death stalwart, especially for communities with high vaccination rates, future outbreaks should—broadly speaking—continue to ease in severity. But waves of infection, some big, some small, will keep coursing through the population.
In the absence of perfect immunity, there can be no hard line between people who have been infected in the past and people who will be infected in the future. It is instead a boundary that people will cross constantly, and not always knowingly, as immunity naturally ebbs and flows. Perhaps better vaccines will come along that help anti-infection shields stick around for longer. But even then, another variant—one that’s a massive departure from both Omicron and our current vaccines—could arrive, and reset our immune landscape “like an Etch-a-Sketch,” says Shweta Bansal, an infectious-disease modeler at Georgetown University. Even in the absence of a total makeover, the coronavirus has plenty of tricks to keep spreading. In South Africa, where cases have once again been ticking up, some unvaccinated people who caught BA.1 just months ago may now be vulnerable to a pair of Omicron-family offshoots, BA.4 and BA.5, that seem to hopscotch over infection-induced immunity, and have already been detected in the U.S.
From the beginning of the pandemic, it seemed very possible that nearly all Americans would eventually be infected by this coronavirus. In recent months, that reality’s come to feel just about inevitable, and may come to pass sooner than many people hoped. With a virus like this, infection won’t be “a one-and-done situation,” Pitzer told me. The virus’s saturating spread may well continue for generations to come; reinfections and vaccinations throughout a person’s lifetime could become, for most of us, a new pathogenic norm. For perspective, Cobey points out that pretty much everyone ends up infected by a flu virus by the time they’re about 10. SARS-CoV-2 spreads even faster, and experts don’t know whether its pace will eventually slow.
“I think if you haven’t gotten it yet, you’re extremely lucky,” Majumder told me. “It reflects privilege,” she said, more than almost anything else: the ability to work from home, access to masks, being up-to-date on vaccines. Majumder and I both check these boxes, likely insulating us against the worst of most exposures; she doesn’t think she’s been infected either. Perhaps there is some biology at play, too. Some people could be genetically less primed to be infected by certain pathogens, even after they’re exposed—a phenomenon well documented with HIV, for instance. Others might be a bit more resilient against contracting the coronavirus because they’re carrying a smidge more immune protection, laid down by the SARS-CoV-2-like pathogens they’ve encountered in their past. But “those are things that affect you on the extreme margins,” Bhattacharya told me, unlikely to account for most of the noncases in the mix.
If the weightiness of mostly infected isn’t super scientifically significant, maybe it’s more a psychological shift. Nations decide what level of transmission, disease, and death they’re willing to live with; a virus’s presence becomes a sort of background noise. People start to see infections as common; individual infections, even outbreaks, stop making front-page news. It’s not an inappropriate transition to make when a country truly is ready for it. A lot has changed in the past two years, and scientists have cooked up tools to cushion the coronavirus’s blow. Pitzer, of Yale’s School of Public Health, benefited from several of them when she caught the virus a few weeks ago. She had a relatively easy go of it, safely isolating at home, thanks to her three doses of vaccine and a speedy course of Paxlovid, “dropped off on my doorstep” within a day of receiving a positive test result.
But most of America isn’t there yet. Pitzer knows that her case was “by far the exception.” Across the country, people have struggled to find and acquire the antiviral, because they’re unable to test, can’t reach a prescriber or a pharmacy, or don’t even know they’re eligible; many who lack paid leave feel compelled to go to work sick. Until we have more equitable access to COVID accoutrement such as treatments, tests, and boosters, experts told me, pandemic-caliber suffering will persist in vulnerable communities. Our roster of tools also remains incomplete. “We still don’t understand very well what the long-term consequences of milder infections are,” or how to prevent or treat them, Cobey told me. And for some people who struggle to mount immune responses, getting infected may never be low-risk; many of these individuals have had to go to unsustainable extremes over the past two years to have a shot at staying safe. All of this leaves the country in a troubling spot, a time when the coronavirus is still very much on the move. Cases are once again ticking upward nationwide, pulling the sick out of work and school, and straining a health-care system that’s been stretched past breaking for years.
Still, the piecemeal nature of immunity against this virus is exactly why the world should feel motivated to keep building it up. “The more immunity to the circulating strain, the better,” Bhattacharya said, and “the longer it’ll take for the virus to spread through.” Even if infections continue to happen, they do not have to happen as frequently as they now do. That sort of equilibrium will take work to achieve and to maintain, as antibody levels ebb over time and new variants crop up. But it’s the difference between recognizing infections as somewhat typical and dismissing them as normal—between recognizing that this virus is a part of our lives going forward, and inviting ourselves to succumb entirely to it.