Omicron is unlikely to have completely outsmarted the vaccines, experts say, even with its unusual array of mutations.
There are a lot of unknowns, but they expect that the shots will still do what they do best: Keep people out of the hospital and out of the grave.
Omicron raised alarms when it was first identified during a sharp spike in cases in South Africa. The World Health Organization added it to its list of variants of concern last week.
The virus contains dozens of mutations, including several that are thought to make it more infectious and others that appear to help it evade the immune system.
"But I think it's still very possible that vaccines will hold up against severe disease, even with those mutations," said Dr. Carlos del Rio, a professor of medicine at Emory University and president-elect of the Infectious Diseases Society of America.
That's what has happened with every variant so far. With delta, he noted, "breakthrough" infections among vaccinated people have increased, but those cases are mostly mild.
Omicron seems to be better able than other variants to infect people who have already had COVID-19, according to early data from South Africa. But people with reinfections generally have not been seriously ill.
Experts are recommending boosters for people who can get them. U.S. officials have authorized them for everyone age 18 and older.
Researchers will have more questions than answers about omicron for the next few weeks while they study the variant. They don't yet know for sure how the virus stacks up against other variants in terms of how easily it infects or how sick it makes its victims.
Hospitalizations have increased in South Africa during the omicron surge, but it's not clear if that's because the virus causes more severe infections or because more people are getting infected. Most of the country is not vaccinated.
Scientists need to figure out whether the rise in infections is "vaccine failure or failure to vaccinate," said Dr. Walter Orenstein, associate director of the Emory University Vaccine Center.
"If it's vaccine failure, is it a problem of time since the last dose and waning immunity?" Orenstein said.
Though it does not yet seem to be necessary, some companies are working on modifying their vaccines to better protect against the new variant.
Moderna and the Pfizer-BioNTech partners say they can have a new vaccine ready in about three months. Johnson & Johnson says it is working on a new version but did not give a timeline. Oxford University told Reuters news agency that the vaccine it produces with AstraZeneca is still highly effective but that it can quickly update it if necessary.
Many companies have started developing modified vaccines against previous variants, but none has gone to regulators for approval.
The U.S. Food and Drug Administration says it will not require drugmakers seeking approval for their updated vaccines to go through a process as lengthy as the one for the original versions. Much like with the annual flu vaccine, a few tests for safety and immune response will do.