It’s no secret that COVID-19 vaccination in the United States has hit a wall of right-wing obstinance. Meanwhile, state and local lockdowns have somehow become even more politically perilous for governors and mayors. The renewed public health gridlock has chilling implications as a dangerous new variant of the novel coronavirus, SARS-CoV-2, becomes dominant in the U.S.
Barring an unexpected and radical change in Americans’ attitudes, all we can do is hold on tight as the Delta variant burns through the country’s unvaccinated millions. The only thing that might stop it, in the least-vaccinated cities and towns, is population-level immunity—herd immunity, to borrow a loaded term. But like any pure herd-immunity scheme, that path is a potentially catastrophic one.
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Herd immunity occurs when enough people have antibodies, either from a vaccine or past infection, to block a virus’ transmission pathways and prevent unprotected people from getting sick. The problem is, we have no idea what herd immunity looks like with the coronavirus, and even less so with this new variant running amok across the country.
It’s possible nearly all unvaccinated residents of low-vax communities would have to catch Delta in order to stop the variant—“lineage” is the scientific term—from reaching the last few unprotected people, experts say.
It gets worse: Letting Delta run its course in the United States not only could expose tens of millions of people to the coronavirus, it might also give the lineage a chance to mutate into an even more aggressive new form. A “Mu” or “Nu” lineage, if we stick with the U.S. Centers for Disease Control and Prevention’s naming convention.
In other words, if herd immunity is the best chance of beating Delta in a country with a big vaccine-hesitancy problem, we’re probably screwed.
“We could just ride out this new variant, but doing so risks great peril to both vaccinated and unvaccinated individuals,” Elias Sayour, an associate professor of neurosurgery and pediatrics at the University of Florida, told The Daily Beast.
There was a time, early in the administration of President Joe Biden, when it seemed like the United States was really going to embrace the high-tech COVID vaccines that the federal government spent so many billions of dollars developing last year. That, in turn, made herd immunity—and some measure of post-COVID normal—look feasible.
This spring, Americans were getting vaccinated at a rate of up to four million doses a day, putting the country on track to vaccinate almost everyone by this fall.
But polling indicated that as many as a fifth of U.S. adults were skeptical of, if not outright hostile to, vaccination. And vaccine-hostility reached a feverish pitch this month as the Biden administration rolled out a program empowering local volunteers to canvas vulnerable neighborhoods in order to encourage vaccination. “What’s next? Knocking on your door to see if you own a gun?” tweeted U.S. congressman Jim Jordan, an Ohio Republican.
It should come as no surprise that vaccination rates have declined—and fast. After peaking at 4.4 million doses on April 8, the daily vax rate steadily dropped to a new low of just 450,000 doses in mid-July. And that’s where it’s stayed for more than a week now.
Four hundred and fifty thousand doses a day is a drop in the bucket in a country of 330 million. As of this week, around 186 million Americans have received at least one dose of one of the three vaccines that the U.S. Food and Drug Administration has approved for widespread use. At the current uptake rate, it could take a year for the rest of the country to get that first jab.
But nationwide numbers are misleading. Vaccination rates vary across states and even within states. Heavily Democratic states, generally speaking, are better vaccinated than heavily Republican states. Cities, which tend to be governed by Democrats, also tend to be better vaccinated than rural communities with their overwhelmingly Republican leadership.
“It is sad that the vaccine has become politicized, since the virus has no political preference or allegiances,” Jennifer Reich, a sociologist at the University of Colorado Denver specializing in vaccination, told The Daily Beast. “Yet political party remains one of the greatest predictors of who is least interested in the vaccine.”
It’s no wonder, then, that in left-leaning Vermont and highly urban and liberal Massachusetts, around three-quarters of residents have gotten at least one dose of vaccine. It’s also no wonder that the least vaccinated states are deep-red, less-urban Arkansas, Mississippi, and Louisiana, where slightly more than a third of residents have gotten one or more jabs.
“It’s almost like it’s going to be two Americas,” Anthony Fauci, head of the U.S. National Institute of Allergy and Infectious Diseases, told CNN last month.
One America has built a solid wall of vaccine-induced immunity against Delta. The other has left the gates wide open.
The numbers are clear. Delta, which first appeared in India in late 2020 and arrived in force in the U.S. this spring, is now the dominant coronavirus lineage almost everywhere in the country. But it’s driving surges in infections mostly in low-vax states.
Delta accounts for at least 90 percent of new COVID cases in both Arkansas and Vermont, epidemiologist Eric Topol concluded, based on data from CoVariants.org. That website, in turn, borrows raw genomic surveillance data from GISAID, the global database for genetic sequences of major infectious diseases.
But Arkansas and Vermont are experiencing very different outcomes, Topol explained on Twitter. Vermont, with its high vaccination rate, has recently registered just two new COVID infections per 100,000 residents—one of the lowest infection rates in the country. Low-vax Arkansas, by contrast, has counted 36 new infections per 100,000 people—the highest infection rate in the U.S. at the moment.
Edwin Michael, an epidemiologist at the Center for Global Health Infectious Disease Research at the University of South Florida, has run simulations of Delta’s spread. He said he’s not surprised at the results. “Our modeling work is showing that while cases are predicted to decline going forward in states that have achieved at least 70 percent vaccinations with at least a single dose, the opposite is true for the states—Alabama, Mississippi, Louisiana, Florida—that have achieved between 35 percent to 55 percent vaccination rates,” Michael said.
It’s unclear whether herd immunity could stop Delta before it does its worst.
Epidemiologists used to guess that a community would effectively block transmission of earlier forms of SARS-CoV-2 once around 70 percent of the population had strong immunity resulting from either vaccination or past infection. For Delta, the threshold could be higher.
Meanwhile, it’s not just cases going up in unprotected states. COVID-related hospitalizations are also on the rise in low-vax communities. Arkansas recently reported 23 coronavirus hospitalizations per 100,000 people, a rate three times higher than the national average. Michael said his simulation anticipates Florida’s hospitals filling up in coming weeks.
On the bright side, COVID-related deaths are increasing, but at a slower rate than cases are increasing. There’s a perverse logic to this.
Because elderly Americans, who are the most vulnerable to COVID, got vaccinated early and at a high rate, as a group they’re better protected against Delta than younger people—an undervaccinated group—tend to be. But younger people who’ve caught COVID have a better survival rate than seniors. So cases can spike without deaths also spiking.
This gap between the surge in cases and the surge in deaths is cold comfort. For starters, COVID can be devastating even in cases where it doesn’t kill you. You might lose lung capacity or suffer permanent heart damage or other effects as part of so-called ”long COVID.” Your medical bills could pile up.
What’s more, Delta still has plenty of room to keep spreading in states that have all but stopped vaccinating, and where a fresh round of social-distancing mandates is a political non-starter. Hospital beds could continue to fill for weeks or months to come. People could continue to get sick and die. We don’t know when or how this ends.
In states such as Arkansas, Delta could be on track to infect about as many unvaccinated people as it wants. Herd immunity might not stop it.
The idea behind herd immunity, in its purest and cruelest form, is to just let an infectious disease run its course through a community without anyone taking any population-level steps to mitigate its transmission. Yes, a lot of people will get sick. Some will die. But the survivors will build up antibodies and, over time, the whole community will become immune as the pathogen finds fewer and fewer viable transmission pathways.
That’s the theory, one that was notoriously embraced in fits and starts by some in the Trump administration last year. But no country has actually fully tested the theory against COVID, for obvious reasons. It’s risky.
Sweden briefly flirted with a herd-immunity approach last year. As much of the world locked down in early 2020, Sweden did nothing. On purpose. A few months later, in June 2020, the Swedish government convened a commission to assess the results of its contrarian policy.
The commission’s findings were startling. By that point, around 5,300 Swedes had died of COVID. By comparison, around 250 people had died in Norway, 330 in Finland, and 600 in Denmark. Adjusted for population size, Sweden had suffered four or five times as many COVID deaths as its neighbors.
The Swedish government swiftly ended its herd-immunity experiment and put in place the same kind of social distancing measures that by then were common across the world.
With new vaccinations slowing to a trickle, lockdowns seemingly off the table, and Delta on the march, under-vaxxed U.S. states are effectively embarking on their own Sweden-style herd-immunity experiments.
Except worse. Swedish leaders at least reserved the option to lock down—and possessed the political will to do so if it came to that. The country also had vaccines to look forward to in case its viral experiment really ran away from it.
By contrast, the deepest-red U.S. states are effectively trying for a version of herd immunity while many of their residents also reject vaccines and social-distancing as back-ups in case the virus gets the upper hand.
Moreover, Delta is more aggressive than the earlier lineages that wreaked so much havoc in Sweden—and, of course, the United States—throughout the last year and a half. Delta includes several changes to its spike protein, the means by which the coronavirus grabs onto and infects our cells. Studies have found Delta to be up to 60 percent more transmissible than other lineages.
Delta might also slightly reduce the effectiveness of the FDA-approved vaccines, all of which are around 90-percent effective against older COVID lineages. To be clear, the vaccines still work against Delta, and work really well by historical standards. That Delta has any impact at all on the jabs’ effectiveness simply underscores how nasty the lineage is.
We don’t know what it will take to get to herd immunity with Delta in part because we’ve never let any coronavirus variant just do its thing, even if some governors did ease lockdowns well before experts thought it was advisable, and before Delta blew up.
“I don't think we ever knew the exact number for herd immunity, but certainly whatever that number was, it might be expected to be higher if we are dealing with a more aggressive and transmissible infection,” Sayour said.
In fact, it’s possible that, for Delta, there is no population-level immunity threshold that’s less than roughly 100 percent. The lineage might just keep finding new transmission pathways until it infects nearly everyone who isn’t already immune. A Delta surge in that scenario would end only when practically everyone is either vaccinated, was recently infected, or is currently infected.
Lawrence Gostin, a Georgetown University global health expert, said he’s reluctantly betting on that bleak outcome. “Without very high and uniform vaccine coverage, I do not foresee us getting to herd immunity,” Gostin told The Daily Beast.
That’s just one possibility, of course. It’s equally possible that Delta burns itself out before it infects everyone who isn’t immune, the way that some older lineages have tended to do.
But even the latter scenario might just offer a temporary reprieve. In the best-case scenario, where Delta runs its course without causing a runaway surge in infections among the unvaccinated, the time and space America’s under-vaxxed communities have given Delta could allow the lineage to mutate into an even more dangerous form.
Remember, Delta didn’t come from nowhere. It’s the product of last year’s explosion in COVID infections. And next year’s COVID will be the result of today’s infections. Vaccination isn’t just about protecting people from pathogens that are currently circulating. It’s about protecting them from the next pathogen, too.
Maybe the United States will get lucky and the Delta surge won’t end up being that bad. But unless a whole lot of vaccine-rejecting Americans change their minds, it’s all but inevitable that there will be another surge in coming months—even after this one—one resulting from whatever new lineage Delta spawns.
“There’s no time limit at which point the virus will just give up,” Niema Moshiri, a geneticist at the University of California, San Diego, told The Daily Beast.
If some future lineage manages to thwart our vaccines in a way Delta has not, then the whole coronavirus pandemic could reset back to zero, only worse. This future new lineage might be the most transmissible yet. And for a while at least, we’d have no vaccine.
“That will prove to be a disaster,” Michael said.
All that is to say, when it comes to COVID—and especially Delta—counting on unvaccinated herd immunity is a bad idea. But right now, it’s the only idea that America’s least-vaxxed states seem comfortable with.
