Why Are We Still Isolating Vaccinated People for 10 Days?

If vaccinated people are less likely to transmit the coronavirus, maybe they should be able to test out of isolation.

a person looking out of a window
Mathieu Thomasset / Hans Lucas / R​edux

For most fully vaccinated people, a breakthrough coronavirus infection will not ruin their health. It will, however, assuming that they follow all the relevant guidelines, ruin at least a week of their life.

That very frustrating week began for Joe Russell on November 11, the day he found out he’d tested positive for the virus, just one month after getting a Pfizer booster, and about five or six days after he’d first felt an annoying tickle in his throat. Russell, a 35-year-old hospital-supply technician in Minnesota, dutifully cloistered himself in his basement, far from his fully vaccinated wife and his fully unvaccinated 2-year-old son, and phoned in sick to work. He stayed there through the 15th—the requisite 10 days past his symptoms’ start. Then, fearful of passing the pathogen to his family, he tacked on one more day, before venturing upstairs on the 17th, still in a mask.

Now back to business as usual (at least, by pandemic standards), Russell wonders if he—a young, healthy, boosted individual—could have ended his saga sooner. His post-vaccination infection, like so many others, wasn’t medically dangerous, and may not have even posed a transmission threat. By the time his isolation started, he was feeling totally fine. He took three more tests during his stint in solitude; all were negative, another hint that his immune system had purged the threat. And yet, even his employers, who don’t offer paid sick leave, insisted that he stay home for several extra days past the end of isolation. The experience was frustrating, lonely, and confusing. More than anything, he told me, “I just wish I was there to help my wife out and, obviously, see my son.”

Russell’s breakthrough was treated as any other SARS-CoV-2 infection would be. But maybe that shouldn’t have been the case. For at least those who have gotten all their necessary shots, we have the data and tools to slash the recommended length of isolation—and the attendant burden—by a lot, possibly even by half. Two years into the pandemic, we’re long overdue for a rethink on how vaccines affect our approach to outbreak control.

One idea involves letting some immunized people test out of confinement, a protocol that universities such as Cornell are already tentatively putting in place. The coronavirus transmission window is thought to be rather brief for most people, peaking around the time symptoms start (if they do at all) and slamming shut in the few days after; vaccines appear to trim that period further down. “It’s clear that vaccination will reduce infectiousness,” Ajay Sethi, an epidemiologist at the University of Wisconsin at Madison, told me. And fully vaccinated folks who repeatedly test negative “are probably not a risk to anybody anymore,” Angela Rasmussen, a virologist at the University of Saskatchewan, told me.

The idea of a truncated isolation might sound dicey, especially as cases once again rise worldwide, and a new variant of concern blazes across the globe. But SARS-CoV-2 isn’t going anywhere; our strongest next moves will involve sustainable policies that help us both combat the pathogen and coexist with it. If we must deal with breakthroughs, the least we can do is make them more bearable.

The goal of a cautious isolation is, of course, to keep sick people from spreading the virus; getting the timing wrong can be disastrous. But we’ve known for many months that the COVID-19 vaccines train immune cells to more swiftly sweep the virus out. Even the CDC acknowledges in its guidance on isolation that “fully vaccinated people are likely infectious for less time than unvaccinated people.”

In the unvaccinated, “it’s clear that the majority of transmission happens early on,” says Müge Çevik, a medical virologist at the University of St. Andrews, in the United Kingdom. The contagious period seems even more limited in the immunized. Scientists scouring airways for scraps of virus genetic material have found that vaccinated individuals seem to evict SARS-CoV-2 far faster than those who haven’t gotten their shots; the immunized may carry a lot of virus initially, but it disappears quickly. That’s true even for Delta and other hyper-transmissible variants, which can rapidly xerox themselves into armies, and may linger for longer than other versions of SARS-CoV-2. Most post-vaccination infections are also asymptomatic or rather mild—cases that, generally speaking, appear to be less contagious.

A subset of vaccinated people will still push pathogenic particles out into the world; the chances of spread are lower, not zero. But “pound for pound, you expect some of that virus to be less potent,” Alex Greninger, a virologist at the University of Washington, told me. Viruses that have been stewing in immunized airways can end up swathed in antibodies that render them less dangerous to others.

A lot of this is common knowledge by now among the experts who design our policies. And yet, American guidelines have not substantially shifted since two summers ago—when, in July of 2020, the CDC said most people should no longer be using tests to determine when to leave isolation. Instead, they could exit 10 days after the start of symptoms or the first positive test result, provided that they no longer felt sick. (People who are seriously ill or immunocompromised might shed the virus for much longer, though, and could require isolation of 20 days or more.) That change happened 17 months ago, at a time when vaccines weren’t authorized, tests were absurdly scarce or slow, and the best option was to estimate how long folks might shed, and tell them to hide away for about that length of time.

Things are very different now. Three super-effective vaccines have been greenlit for use in the United States, and hundreds of millions of Americans are doubly or triply dosed. Tests are faster and more available. And we know a lot more about how and when the virus spreads. The CDC has even been emboldened to modify its rules on quarantining after an exposure to a COVID case. The policy used to be 14 days of solitude for everyone. Now vaccinated people don’t have to quarantine at all. Even the unvaccinated can peace out at 10 days, or even seven, if they produce a negative test—a change that went into effect in December 2020.

I asked the CDC if it would consider amending its isolation policies for the fully vaccinated. Jasmine Reed, an agency spokesperson, said only that “any changes to shortening isolation or quarantine guidance will be made based on science and research.” But nothing in the current recommendations on ending isolation yet reflects how vaccination has changed the game.

Rasmussen wishes the rules for isolating immunized people were different as well. Because she’s thrice vaccinated, awaiting coronavirus test results now makes her nervous not because she’s worried about getting super sick or dying, she told me, but because a positive would be “a huge pain.” Çevik agrees. Confronted with the prospect of a 10-day isolation, some people will “hesitate to take the test to start with,” she said. For the vaccinated, “probably five to seven days [of isolation] would be enough,” and compliance would go up. Perhaps a few contagious cases might be missed. But a seven-day isolation would still be far better than none at all.

In the absence of federal guidance, some institutions are taking matters into their own hands. Cornell, in partnership with the health department in Tompkins County, New York, is piloting a protocol that lets vaccinated-then-infected students exit isolation as early as five days in, after producing two negative PCR tests. “We think their viral loads drop very quickly,” Frank Kruppa, the public-health director of Tompkins County, told me. “If they don’t have the virus in their body anymore, there is no need to remain in isolation.”

Right now, only asymptomatic cases qualify, and students can’t take their first in-isolation test until day three. If that’s negative, they test again on day five. (If that third-day test is positive, but the fifth-day test is negative, they get another chance to test on day seven.) In this way, there’s a built-in insurance policy: A pair of negatives, separated by two days, helps confirm that a low-level infection isn’t being missed.

The program doesn’t yet have results to share: In the couple of months since Cornell began the pilot, fewer than 25 students have enrolled, according to Gary Koretzky, Vice Provost for Academic Integration at Cornell University. (Media representatives at Duke, another university that’s tinkering with mini-isolations, declined to comment on their own program.) But if experiments like these pan out, they could pave the path to much more palatable public-health policies on a larger scale. Kruppa hopes to eventually expand the program to all of Tompkins County, where about 75 percent of residents are fully vaccinated. At some point, symptomatic breakthroughs could be eligible as well; officials might also try different testing timelines, or rapid tests. But that all hinges on how the Cornell pilot goes. “It will be stepwise,” Kruppa told me.

There are still kinks to work out too. Vaccines don’t take quite as well in individuals who are older or immunocompromised, and the sicker people are with COVID-19, the longer they seem to maintain the virus in their airway, and probably shed it. (There are exceptions to this, including people with long COVID, who may have symptoms for months after they stop being infectious.) Shots can’t guarantee that all breakthrough transmission periods will be brief. And our knowledge of post-vaccination transmission periods might change over time: Antibody levels decline in the months after vaccination, which means the shots’ protection against transmission also likely ebbs. (Boosters, for what it’s worth, seem to rocket antibody numbers way back up, though how long those effects last is unclear.) New variants, too, could muddle the math. And although new antivirals, administered early, might curb contagiousness, researchers are still figuring out how to best deploy them.

Testing also comes with caveats. PCR tests are so sensitive that experts can almost always trust their negatives to mean the virus isn’t there. But these tests can’t distinguish between an intact, infectious pathogen, and debris left behind by a successful immunological attack. Some people who are no longer contagious may still test positive by PCR for weeks. (The CDC actually recommends against retesting people by PCR for 90 days after they receive a positive result.) Although rapid antigen tests, which pick up on infections only with moderate to high levels of virus, could offer an alternative, Koretzky worries that they’d overlook contagion and undermine the program. “The false negatives were unacceptable in our mind,” he told me. “We wanted to err on the side of being conservative.” There’s also no telling how Cornell’s pilot will translate to a nonuniversity setting. More than 97 percent of people on campus are vaccinated—far above the national average.

Sorting through these questions, though, means moving on from policies designed for a pre-inoculation world. “Are we isolating people because they represent a risk?” Koretzky said. “Or because it’s protocol?” The point, after all, is flexibility. As experts finagle the details, Saskia Popescu, an infection-prevention expert at George Mason University, recommends a compromise: “No symptoms? No shedding? Take them out of isolation, but also, wear a mask.”

Tackling the isolation issue could be a bellwether for more change. Post-vaccination infections will keep happening. “That’s inevitable,” Sethi, of the University of Wisconsin, told me. And every case still poses a potential threat to the person who’s caught the virus, and the people around them. The world will need to find the right policies around masking, vaccination, testing, and support for those in isolation to keep cases in check in a sustainable way.

We haven’t yet found a middle ground between catastrophizing post-vaccination infections and trivializing them. “We have to make it clear to people that getting COVID unvaccinated is really bad,” Ashish Jha, the dean of Brown University’s School of Public Health, told me. “But in a vaccinated population? We can think about it very, very differently.” Perhaps acknowledging how vaccines transform our experience of COVID, and using that info to guide decision making, is a first step toward carving out that in-between space.