Omicron Has Created a Whole New Booster Logic

For a while I was on the fence about getting another shot. Then came the newest variant of concern.

Bottles of the Pfizer-BioNTech vaccine
Laurent Coust / Sipa / AP

The day before I got my COVID booster shot, news of the variant we’re now calling Omicron erupted around the world.

Mere hours earlier, I’d been on the fence about boosting, as I had been for months. I’m relatively young and healthy; I’d had two doses of Pfizer in the spring. And although a boost would probably benefit me, I didn’t feel like I necessarily needed it now—a stance that, comfortingly, was shared by several of the pandemic experts I spoke with regularly. Marion Pepper, an immunologist at the University of Washington, had been “waiting for something to add urgency,” she told me. Müge Çevik, a medical virologist at the University of St. Andrews, in the United Kingdom, has been “looking at the data” before she got another shot. And Mónica Feliú Mójer, of the nonprofit Ciencia Puerto Rico, is now boosted, but delayed the dose over concerns about global vaccine equity. While much of the world waited for their first shots, I felt perfectly comfortable with the protection I’d already built up.

Then there was Omicron—which became the clincher in my decision to boost. This version of the virus looked worrisome, freckled with genetic changes that might enhance its transmissibility or stealth. SARS-CoV-2 seemed poised to deliver another punch. So I raised my guard in return.

Having a new variant around rejiggers the pandemic risk landscape, and that landscape is now looking less favorable to us. Pfizer, for instance, now says that, based on early data, a booster might be necessary to maintain a high level of protection against Omicron. Booster uptake’s been somewhat spotty, though, even among people for whom it’s been recommended since September. About one in four fully vaccinated adults says they will either “probably not” or “definitely not” boost, according to a recent Kaiser Family Foundation poll. And more than half of inoculated adults over 65—one of the groups at highest risk of severe COVID-19, and one of the earliest groups to be urged to vaccinate again—have not received an additional injection.

No single concern is keeping millions of eligible Americans on the booster fence, and some of these numbers almost certainly reflect a pre-Omicron mindset. Anecdotally, I’m hearing from experts, colleagues, friends, and family that finding a booster appointment in many parts of the country is now nearly impossible. But a few key questions seem to be percolating on repeat. Here’s a rundown of the thinking that helped some of the now-boosted reckon with the choice—and roll up our sleeves again.

Do I really need a booster?

Understanding the benefits of boosting now means acknowledging two truths. Our vaccines are still doing an extraordinary job of staving off really serious disease. And adding an extra dose will probably keep people even safer.

When COVID vaccines first started rolling out last winter, they were an absolute knockout on just about every metric by which they were measured, not only preventing serious disease and death, but also limiting infections and transmission to a very high degree. Now, several months out, more vaccinated people are briefly contracting the coronavirus, and maybe getting a little sick as antibody levels naturally tick down over time. But the vaccines are still “stellar enough to keep most people from being hospitalized and very sick,” Luciana Borio, a senior global-health fellow at the Council on Foreign Relations, told me. That’s thanks to a legion of immune-memory cells that can pump out more antibodies when needed, or blow up virus-infected cells. Those hyper-durable defenses take some time to kick in, though, and can’t block all mild cases.

Boosters, then, remind the immune system of an old threat, lifting antibody levels and recruiting new immune cells to the front lines. People who receive boosters are less likely to get infected than those who don’t: The shots are clearly conferring benefits, though the jury’s still out on how long they’ll last. The pluses are especially big for people who are older, and they’re essential for the immunocompromised (who probably needed a three-dose vaccine to begin with).

For everyone else, boosting has looked more like a perk than a must-have: If defenses against the most serious forms of COVID-19 were holding, a touch-up wasn’t urgent.

But a vaccine’s effectiveness can be chipped away from two ends: a drop in the body’s defenses, and a swell in the virus’s offenses. And Omicron has clearly raised the stakes. The variant’s genome is laced with dozens of mutations that weren’t present in its predecessors’. Even if my body retained a perfect memory of my vaccines’ contents, these changes might still bamboozle it.

“That’s what changed my thinking about booster doses,” Çevik told me. Because of the mismatch between variant and vaccine, she said, there will be a “significant drop” in our antibodies’ ability to protect us from milder outcomes, a trend that appears to be borne out by early data. An extra dose of vaccine—even one that’s an imperfect pantomime of Omicron—would shore up important defenses in advance of a surge. A drop in antibody protection would likely still happen because of Omicron’s genetic quirks, but the fall would be cushioned by sheer quantity—a trend that a press release from Pfizer now appears to confirm.

We’re also still dealing with Delta, a variant that vaccines definitely keep in check, especially as we head into the holidays. “So this could be a double whammy,” Pepper, of the University of Washington, told me. (She, for one, is probably going to boost soon.) While case rates remain high, reinforcing protections against infection and transmission could cocoon the still-vulnerable, and tamp down outbreaks.

Shouldn’t we be holding out for an Omicron booster?

If we could, then, yes, the ideal defense against Omicron would involve inoculating everyone (everyone) with a vaccine that’s a perfect match for the variant. To some, boosting with a vaccine modeled on the now-obsolete OG coronavirus might feel a bit like upgrading to an iPhone SE three months before an iPhone 13 mega-sale.

And yet, every expert I’ve spoken with in the past couple of weeks has delivered an unequivocal verdict: Boosting now is still the right choice—to get ahead of Omicron, to prepare ourselves. A bespoke Omicron recipe isn’t yet available, and won’t be for at least a few months. “The goal is to provide interim protection” before the wave of Omicron crests, Taia Wang, a physician and immunologist at Stanford, told me. And we may never need an Omicron-specific booster, making a wait unwise. Omicron’s genetic tweaks make it a touch unfamiliar, but not completely unrecognizable. Additional doses of vaccine have been shown to enhance the quantity and quality of antibodies that can thwart all known coronavirus variants.

Even if an Omicron-specific vaccine is on the horizon, immunologists told me that people should be able to get both, if they need to—OG now, Omi-vax later. That could be warranted if Omicron’s really, really good at dodging some of our immune defenses. In that case, getting an Omicron-keyed booster would almost be like rolling out an entirely new vaccine. It would coax our body into recruiting fresh crops of immune cells to fight, rather than only marshaling old ones back to the fore.

If we’re boosting so often, won’t side effects get worse?

This is one of the most common concerns I’ve heard. Some people had such rough experiences with their first set of vaccines that they’ve been so far unwilling to sign up for a repeat. Side effects can mean taking time off work, or sleeping through an entire weekend—and on very rare occasions, even worse outcomes.

Second shots, on average, were tougher to take than the first. But that doesn’t mean the third shot will ratchet up the gnarliness. Vaccine makers have found that boosters’ side-effect profile is actually pretty comparable to that of the initial two doses, or somewhere in between them. The body’s had months to calm down since its last exposure. And for those on Team Moderna, the booster’s just a half dose—less likely to rile cells up.

A few other people I spoke with worried that boosting now would mean they’d have to boost again, and again, and again. That won’t necessarily be the case: Some experts hope that a third dose will, for at least the mRNA vaccines, take us up to a new and lasting level of protection. In that optimistic scenario, we might not need another dose of vaccine, or another bout of side effects, for a long time—unless, of course, more problem variants show up.

Several people also raised concerns over the very rare, but very serious, side effects that have been linked to the vaccines—the blood clots that have occasionally followed the Johnson & Johnson shot, and the heart inflammation that can appear after mRNA vaccination. These events are so uncommon that even large trials can’t always identify them, and researchers are still trying to figure out how often they occur after boosts. Still, Taison Bell, a critical-care physician at UVA Health, told me that the chances of a severe side effect popping up after a booster dose remain, in absolute terms, extremely low. And the calculus is clear: Eventually, “all of us will be exposed to the virus,” he said. That’s the framework folks should be using when deciding to boost: The risk of experiencing a truly negative health outcome “is much higher with COVID itself.”

What about vaccine equity?

Boosters, by lifting up antibody levels, make bodies less hospitable to the virus; that cuts the conduits the pathogen needs to travel. On a population scale, that logically translates into trimmer, tamer outbreaks—but boosters alone can’t be pandemic-enders, especially when so many people remain entirely unvaccinated. Omicron might be shifting the conversation on boosters, Feliú Mójer said. “But getting the unvaccinated vaccinated is more important.”

Declining a boost in the U.S. won’t magically inject a vaccine into the arm of someone in Burundi, one of several African countries with immunization rates below 1 percent. But the heavy focus on boosters in wealthy countries risks diverting attention, resources, and human power away from administering first doses, the goal most prioritized by the World Health Organization. It also sends a pretty strong signal about where nations’ priorities lie. At this point, the number of American booster doses that have been doled out exceeds the number of primary injections that have been given in most other countries. Neglecting vaccine equity can also have compounding consequences: The more people who remain unprotected, the more variants will surely arise.

Of all the concerns on this list, this last one weighs most heavily on my mind. And it’s certainly causing people who otherwise see the benefit of boosters to take pause. Çevik thinks boosters make more sense now than they did before, and she’s probably going to get one herself, but “I’m still standing behind the ethical aspects.” She and Borio also pointed to the continued power of masking, distancing, testing, ventilation—the tools we’ve relied on for almost two years.

Céline Gounder, an infectious-disease physician at Bellevue Hospital Center in New York, previously pushed back against boosters for all and had, prior to the rise of Omicron, put off her own additional dose for months. Now she’s signing up for another shot. Gounder still feels that the topmost goal is to prevent severe disease, which the vaccines continue to do. “I still believe all that I’ve said before,” she told me. “But there’s more than one reason to boost.”