Dr. Rochelle Walensky, Director of the Centers for Disease Control and Prevention (CDC) speaks during an interview with the Associated Press on Wednesday, Dec. 8, 2021, in Atlanta. Credit: Brynn Anderson / AP

WASHINGTON — Omicron is rapidly spreading and could become the predominant variant of the coronavirus in the United States “on the order of weeks” over the delta variant, Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said Tuesday.

New CDC data released earlier Tuesday showed that omicron now makes up 3 percent of all sequenced cases of COVID-19 across the country, and roughly 13 percent in New York and New Jersey.

“We’ve seen it compete pretty aggressively with the delta variant in other countries, namely the U.K. and Denmark, and we are anticipating that we will have more cases,” Walensky said in an interview with McClatchy. “It may well be able to outcompete delta. I think we’re still on the order of weeks.”

“What we have seen in these other countries is a doubling time of omicron of around two days, which is really rapid doubling time. So I anticipate if the same were to hold true here that that would be the order of time that we’d start to see it outcompete delta and be the majority,” she added.

Since the summer, the delta variant has accounted for roughly 99 percent of all cases in the United States. But omicron has “eclipsed” delta in terms of transmissibility, Walensky said. “I think from a respiratory virus standpoint, this would be high up there among the most transmissible,” she said.

While omicron has proven extremely contagious, scientists and public health experts have received several pieces of good news from studies and data on the variant in the weeks since it first emerged.

Two doses of the existing vaccines still provide some immunity against the new variant, and a third “booster” dose provides strong protection. Another natural layer of protection, from T cells in the immune system, appears to provide an additional layer of defense against omicron.

Hospitalization rates and average lengths of hospital stays in countries that have seen large surges of omicron cases have been much lower than in previous waves. But Walensky says more data is needed to understand how omicron will affect the U.S. population.

“I think we still need some clarity on, when applied to our United States setting with regards to who’s been vaccinated, who’s been boosted, who’s been previously infected, how severe will omicron be — and then really how well do our vaccines stack up against the omicron, not only for preventing infection entirely, but in preventing severe disease and hospitalization,” Walensky said.

“If you have twice as many infections and half the amount of severe disease, you still have a lot of severe disease,” she said. “So we do need to be careful and just make sure people recognize that all of those parameters matter, which is why prevention is so key right now.”

The emergence of omicron prompted the largest surge in vaccination rates since the spring, when COVID-19 vaccines first became available. Walensky said that roughly 2 million people are getting vaccinated a day — half with the initial regimen, and half with booster shots.

“We know we have many of the tools, and that those tools are effective against all variants — not just the ones that we’ve seen, but likely the ones that we haven’t seen yet,” Walensky said.

She encouraged Americans to continue to adhere to the measures that have become commonplace over the past two years: wear masks, socially distance and get vaccinated.

While a “massive surge” of omicron cases is possible, Walensky said Americans can still enjoy the holiday season. “Don’t rethink your holiday plans,” she said. “Just rethink how you’re going to do it.”

“My best-case scenario is that people rush to go and get vaccinated, they rush to go and get boosted, and we have a huge amount of community protection against this variant. In the meantime, people are taking care of themselves and one another by masking, and that we’re able to avert a massive surge of omicron,” she said. “I think all of that is very possible.”

“Should all of those things not happen, and omicron demonstrates that it has the capacity to lead to the severity of illness seen in prior waves — we’ve seen what happened before,” she said.

Michael Wilner, McClatchy Washington Bureau