We Know a Lot More About Omicron Now

Here’s how to think about all the emerging data.

A photo illustration of a girl wondering with a pencil and a notebook in hand, looking at coronavirus particles floating around her.
Chaloner Woods / Getty; The Atlantic

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The flood of Omicron news can be overwhelming. The endless data, anecdotes, and studies are hard enough to synthesize. But what makes the information even harder to parse is that so much evidence (i.e., what people are seeing) is intertwined with opinion (i.e., what people are hoping and fearing). To round up the week’s Omicron news, I wanted to write something that disentangled evidence and opinion, to help people make decisions right now—about travel, and school, and weddings, and funerals, and holidays—even though we’re dealing with lots of imperfect information.

Consider this your highly imperfect guide to our highly imperfect understanding of Omicron.


  • Omicron is spreading really, really fast. New cases are rising faster than any previous wave in South Africa, even though the country already has widespread immunity from vaccines and a very large Delta wave. The estimated reproduction rate of Omicron is higher than anything the country has seen since the start of the pandemic.

  • So far, Omicron seems to be associated with less severe illness and fewer ICU admissions. Data from Gauteng province in South Africa show that the share of hospitalized patients with COVID who are in the ICU or on a ventilator is 50 to 70 percent lower than it was during the same stage of Delta. What’s more, the average hospital patient is being discharged faster than during the Delta wave. That’s according to data from the National Institute for Communicable Diseases shared with the Financial Times. Doctors from the Tshwane District, at the epicenter of the Omicron wave, reported the same thing: The COVID-positive patients in their hospital were less likely to need oxygen support, and their time in the hospital was shorter than it was for patients during the Delta wave.

  • Anecdotally, a lot of South African doctors say they’re very concerned about reinfections but less panicked about severe illness. “We are seeing breakthrough infections of people who have been vaccinated, but the infections we’re seeing are very mild to moderate,” Richard Friedland, the CEO of a large private health-care network in South Africa, told Bloomberg. “It’s early, but I’m less panicked.” I wouldn’t put much stock in anecdotes. But these are from doctors on the front lines of the outbreak, and their assessments are backed up by the hard data.

Upshot: Omicron is spreading fast in South Africa, and it may do the same everywhere else. The U.K. expects it to be the dominant variant there within a month. But the typical infected person seems, for now, to have milder symptoms than patients experienced with previous strains. Hospitalized patients in South Africa are less likely to go to the ICU or need oxygen.

So does this mean that the coronavirus has simply mutated to become more contagious and less severe? That’s harder to say. It’s possible that Omicron is similarly virulent to the original coronavirus strain, but South Africa’s vaccination and high exposure to Delta gave its population above-average natural immunity. Plus, the United States is older than South Africa, with a different mix of vaccination and Delta exposure, so we don’t want to rush an overconfident direct comparison.


  • The South African study
    The Africa Health Research Institute published a small, rapid, preliminary study that found a huge drop in neutralizing antibodies against Omicron, relative to previous variants, among people with two shots of the Pfizer vaccine. This suggests—but does not prove—that two doses of the vaccine may be less likely to protect against Omicron infection.

    But the study also found that people with hybrid immunity—prior infection, plus vaccination—were much better protected. That might be good news for people with booster shots. “Neutralizing breadth in hybrid immunity is outstanding,” Shane Crotty, a professor at the La Jolla Institute for Immunology, wrote on Twitter. “And we know that 3-dose (boosted) vaccine partially recapitulates that improvement in breadth.” Others agree. “We believe that three doses of the vaccine—so a properly boosted vaccine—effectively simulates the response you get from infection and vaccination with two doses,” the former FDA commissioner and current Pfizer board member Scott Gottlieb said on CNBC.

    A quick note on methodology: This study looked at the plasma from individuals who had been vaccinated or infected to measure neutralizing antibodies in response to Omicron. These antibodies are small molecules that bind to the surface of viruses to keep them from latching on to host cells. They are an important part of the immune system, but they’re not everything. Killer T cells also come in and demolish the viruses, but researchers are less able to measure T-cell response in rapid tests like these. We might have to wait a few more weeks for labs to give us a better understanding of the risk of severe illness.

  • The Swedish and German studies
    In another small study, researchers from Stockholm’s Karolinska Institute found that the loss of neutralization against Omicron was “certainly worse than” against “Delta, but, again, not as extreme as we expected.” Like the South African study, this research looked at the plasma from individuals who have been vaccinated or infected, which can’t tell us the full story about symptomatic infection or disease.

    In Germany, the virologist Sandra Ciesek published less hopeful findings that at least one scientist said portended “disaster.” But overall, Ciesek’s findings tell the same story as the Swedish and South African studies: Antibodies collected from people with two doses of the Pfizer vaccine fared poorly against Omicron. Vaccinated people with a previous infection fared better.

  • The Pfizer study
    Pfizer and BioNTech published the results of their own preliminary lab studies on Wednesday. They found that two doses of the Pfizer vaccine show “significantly reduced” neutralization against Omicron—which, again, is in line with the plasma studies. But three doses of the vaccine appeared to provide the same level of neutralizing antibodies against Omicron as two doses did against the original strain. The company says that it is still working on an Omicron-specific vaccine, which could be ready as early as March.

Upshot: The preliminary studies strongly suggest that vaccinated people are vulnerable to breakthrough Omicron infections. They also make a strong case for getting a booster shot if you want to increase your antibodies and avoid such an infection. If Pfizer’s preliminary data are accurate, Omicron evades the fading immunity from two shots, but a booster should provide an effective counterpunch to the variant.


  • A New York anime convention: All attendees over age 12 at the Anime NYC convention in November were required to have at least one shot. One attendee, Peter McGinn, came home and tested positive for Omicron. Of the 30 to 35 people he spent time with in New York, 15 also tested positive for COVID. Of those, 14 had mild symptoms (McGinn thought he might have had a mild cold, nothing more), and one “had a bad day” but didn’t need to go to the hospital.

  • A Norway Christmas party: All attendees at a Christmas party in Oslo were vaccinated and all had to take a rapid test the day before. Of the 120 people present—some of whom had recently traveled to South Africa—more than half later tested positive for COVID, and many are confirmed to have been infected with Omicron. They have reportedly experienced a range of cold-like symptoms, with no serious cases.

Upshot: These are just anecdotes, but their lessons line up with the conclusions from preliminary research: Omicron could be rough for breakthroughs and contagiousness, but vaccines may well protect against severe illness. Other countries are reporting similar findings. On Wednesday, the European Centre for Disease Prevention and Control released a statement concluding, “All cases for which there is available information on severity were either asymptomatic or mild. No deaths have been reported among these cases so far.”

Here’s what I’m thinking now, subject to major revisions if new information comes out that explodes these hypotheses.

1. Omicron is more transmissible than Delta and will spread faster than Delta in many places. This can be true because Omicron is innately more infectious, or because it is more likely to break through against one or two vaccine shots, or because of some combination of the two factors. If people’s behavior changes dramatically in the face of this fear, that could have a mitigating effect on spread.

2. Omicron will cause more breakthrough infections. It’s already demonstrated extraordinary infectiousness in highly vaccinated areas in South Africa, New York, and Oslo. I don’t expect these examples to be outliers. We should be prepared for Omicron cases to explode in the U.S. and around the world.

3. Omicron will produce less severe illness per infection than previous strains—but it could still produce a lot of hospitalizations, especially among the elderly, if total infections skyrocket. This conclusion is in line with everything we’re hearing from South Africa, Europe, and the outbreaks in New York and Oslo. I expect U.S. hospitalization rates as a share of cases to be lower than what we saw for previous strains. But that doesn’t mean total hospitalizations will be lower. Quite the opposite: It’s possible that Omicron produces less severity per case but also that the U.S. gets deluged with COVID cases, producing a very large surge in hospitalizations on top of the ongoing Delta wave. In particular, the elderly have lower T cell counts, which could make older Americans—and, especially, U.S. nursing homes—particularly vulnerable to Omicron.

4. Get your booster shot. Americans cannot control much about the course of the pandemic. This is something most of us can control: Choose to boost. This would be good advice even if Omicron didn’t exist. Delta is already surging again in the U.S., and we’re seeing hospitalizations surge with it.

5. I’m worried about the global South: Booster shots aren’t as available to most low-income countries, and the full-vaccination rate across Africa is pitiful. In Cameroon, it’s less than 3 percent. In Nigeria, it’s less than 2 percent. In Chad, it’s less than 1 percent. Even if Omicron is inherently less severe, cases could still overwhelm some of these countries’ hospitals and cause major disruptions. Parallel to the pharmaceutical companies working on an Omicron-specific vaccine, the acceleration of global vaccine manufacturing is essential. The emergence of Omicron is a reminder that globalization knit humanity into shared networks—a virus or variant that emerges in China or southern Africa can infect thousands of people across the ocean in days. We’re still all in this together.