Omicron’s Best- and Worst-Case Scenarios

A new, highly contagious variant could have terrible consequences. But if it ends up causing milder symptoms than Delta, there’s a real upside.

World, meet Omicron; Omicron, meet a lot of people who are very, very anxious to know more about you.

The arrival of the newest coronavirus variant, first identified in Botswana and South Africa and now present in the United States, might be bad news, or it might be terrible news—or maybe it’s just a temporary distraction from Delta. Ultimately, Omicron’s effect on the course of the pandemic will be determined by three factors: its transmissibility; the degree to which it evades our existing immune defenses; and its virulence, or the severity of the disease that it causes. If Omicron turns out to jump between hosts with ease, blow past our neutralizing antibodies, and cause unusually dangerous complications, we’ll all be in deep trouble. But it could also turn out to do a lot of other things, with more subtle implications. If Omicron ends up being super contagious, for example, but mild in its symptoms, that might even be a good thing—a perfect variant, just in time for Christmas.

At this point, living with the coronavirus for years to come is all but inevitable. In many countries that have had vaccines in hand for the better part of a year, inoculation rates still aren’t close to 100 percent. Even if every human on Earth gained a degree of immunity from vaccination or infection, the virus could retreat into its many animal hosts, only to reenter the human population in a slightly different form. “There’s no reasonable person, I think, in public health now who thinks that eradication or elimination or having zero COVID is a realistic goal,” says Tara Kirk Sell, a senior scholar at the Johns Hopkins Center for Health Security.

Given that this enemy cannot be vanquished, we’d all stand a better chance at survival if it were armed with a slingshot rather than a cannon. Doctors from South Africa and Israel have said that cases of Omicron seem to be less serious than Delta, so far. Zero severe cases or deaths have been reported among the nearly 60 confirmed cases in the European Union. But the data are very limited and prone to bias. Fewer than 250 cases have been reported worldwide, and the plurality of them are from South Africa, where a younger-than-average populace might be less susceptible to COVID complications in general.

If Omicron continues to show signs of being milder than Delta, that’s good news, of course. But if it also turns out to spread more quickly than Delta, that could be great news. When two variants are circulating, the one that infects more people more quickly will tend to dominate, said Samuel Scarpino, of the Rockefeller Foundation’s Pandemic Prevention Institute. That variant could win out either because it replicates more quickly in its human hosts and spreads more efficiently between them—that is, it’s more transmissible—or because it more deftly evades the immunity we already have.

Immune escape sounds especially scary; after such a hard-fought battle to stay healthy until the vaccines arrived, or a hard-fought battle against the virus itself, no one wants to be told they’re susceptible again. But a reinfecting variant that doesn’t come with the risk of chronic symptoms or ventilators might not be such a bad thing, Elizabeth Halloran, a biostatistician at Fred Hutchinson Cancer Research Center, told me. “If it can get around the vaccines, but in the end really causes less severe disease, that’s probably a step in the right direction.”

One possible downside to a super-contagious (or immune-evading), super-mild Omicron would be that those who catch it won’t end up with much protection afterward, Scarpino said. As my colleague Katherine J. Wu has reported, mild COVID cases may not lead the immune system to produce as many antibodies as do more serious illnesses. But Ali Ellebedy, an immunologist at Washington University in St. Louis, told me that mild infection doesn’t necessarily preclude a robust immune response. “Once you have a productive infection, your immune system has been engaged,” he told me. Even if you don’t feel sick, your body might be pumping out antibodies and training up T cells to fight off the invader the next time it arrives. And by stimulating even a relatively gentle immune response in enough people, a new, widespread version of the virus would make the global population that much better prepared for the future. “Any variant that comes will make it harder for the variant that comes next,” Ellebedy said.

Omicron could, of course, turn out to be pretty much anything. Maybe it’s somewhat more transmissible than Delta, but no more virulent; that, Kirk Sell said, could send us back to stricter masking and social-distancing programs for a while. Or else it might be less transmissible than Delta, and no better at slipping past our immune barriers, in which case “it’s going to be a blip on the horizon” regardless of how virulent it is, according to Halloran. If that happens, we’ll effectively be back where we were two weeks ago: stuck with Delta and waiting for the next shoe to drop.

There are worse fates. “In some ways, Delta is the ideal variant,” Scarpino said: It’s transmissible enough to dominate more dangerous variants, and its virulence can be controlled through vaccination. In the next few weeks, we’ll find out whether Omicron will have its own silver lining—or whether it’ll be catastrophically worse.