(ATLANTA) — With the omicron variant now detected in at least 16 states in the U.S., Centers for Disease Control Director Dr. Rochelle Walensky said the agency is “following them closely” and that the number is “likely to rise.”

Walensky told This Week co-anchor Martha Raddatz that the CDC is still uncertain how transmissible the new variant is and how effective approved COVID-19 vaccines will work against it.

“We know it has many mutations, more mutations than prior variants,” she said. “Many of those mutations have been associated with more transmissible variants, with evasion of some of our therapeutics, and potentially evasion of some of our immunity, and that’s what we’re watching really carefully.”

The main concern right now, according to Walensky, is the dominant delta variant in the U.S. and the thousands of cases being diagnosed each day.

“We have about 90 to 100,000 cases a day right now in the United States, and 99.9% of them are the delta variant,” she said.

But South African studies have so far shown that omicron is about twice as transmissible as delta, and when pressed by Raddatz on what that means for the next six months in the U.S., Walensky said it depends on how the public mobilizes together.

“We know from a vaccine standpoint that the more mutations a single variant has, the more immunity you really need to have in order to combat that variant, which is why right now we’re really pushing to get more people vaccinated and more people boosted to really boost that immunity in every single individual,” Walensky said.

She said the CDC is “hopeful” that current vaccines will work to at least prevent severe disease and keep people out of the hospital.

Moderna is currently working on an omicron-specific booster should it be needed and Stephen Hoge, president of Moderna, said it could be ready early next year.

In an exclusive interview with Raddatz last week, Hoge said that a new variant-specific vaccine would be needed if the level of efficacy dropped below 50%.

Efficacy is a “really interesting, important question, but efficacy is sort of in itself on a spectrum,” Walensky said.

“Is it efficacy of preventing disease entirely? Preventing infection entirely, even if it just leads to a runny nose? Or is it efficacy of making sure people stay out of the hospital and prevent death?” Walensky questioned. “Certainly, we want to do the latter, absolutely first. And we’d really like to do the former as well.”

Walensky also said that the Food and Drug Administration is already in “conversations” with vaccine makers to streamline the authorization process of an omicron-specific booster and that the CDC would be moving “swiftly” after that approval.

When Raddatz asked how the U.S. can help to get even more shots into arms around the world and whether the omicron variant would have even appeared if more people in South Africa were vaccinated, Walensky touted U.S. donation efforts.

The Biden administration has pledged to donate more than 1 billion vaccine doses. According to the Kaiser Family Foundation, as of Dec. 5, over 237 million doses have been delivered, 45 million have been shipped, leaving nearly 817 million pledged doses yet to be distributed. The White House has pledged to deliver 200 million more doses in the next 100 days to countries in need.

“We’re not only donating the vaccines for free and providing more vaccines to the globe than any — than every other country combined, but we at CDC work in 60 other countries providing on the ground assistance in vaccine safety and vaccine delivery and vaccine confidence, in vaccine effectiveness studies.”

Pressed by Raddatz if she fears a worst case scenario is possible with the omicron variant, Walensky said health experts are better situated to tackle the virus now than when it first appeared.

“We have so many more tools now than we did a year ago,” she said. “We know so many things that work against SARS-CoV-2, the virus that causes COVID, regardless of the variant that we’ve seen before.”

Walensky said getting immunity from the COVID-19 right now is “critically important” and continued to stress the importance of CDC regulations such as masking up in areas with high or substantial transmission.

The CDC director dismissed the idea of a nationwide mask mandate when Raddatz asked and said she’d “rather see people get vaccinated, boosted and follow our recommendations.”

“I’d rather not have requirements in order to do so,” she said. “People should do this for themselves.”

Copyright © 2021, ABC Audio. All rights reserved.