Americans need to be prepared to do “anything and everything” to fight the omicron Covid variant, U.S. infectious disease expert Dr. Anthony Fauci said Sunday.

Still, it’s “too early to say” whether lockdowns or new mandates will be appropriate, Fauci said on ABC’s “This Week.”

The World Health Organization last week classified omicron as a “variant of concern,” meaning it is more contagious, more virulent or more skilled at evading public health measures, vaccines and therapeutics.

The variant, first discovered in South Africa, has several mutations to the spike protein that allows the virus to enter the body, and some of those mutations could lead to increased antibody resistance and transmissibility.

The U.S. had already said it would restrict travel for non-U.S. citizens from South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi. The variant has been found in the U.K., Israel, Belgium, the Netherlands, Germany, Italy, Australia and Hong Kong, but not yet in the U.S.

“Inevitably, it will be here. The question is will we be prepared for it? If and when, and it’s going to be when, it comes here hopefully we will be ready for it,” Fauci added.

Biotech companies have sprung into action to fight against omicron. Moderna’s Chief Medical Officer Paul Burton said Sunday the vaccine maker could roll out a reformulated vaccine against the omicron coronavirus variant early next year. Although it’s not clear whether new formulations will be needed or if current vaccines will provide appropriate protection.

Fauci said unvaccinated people should still get available Covid vaccinations, per the recommendations of the Centers for Disease Control and Prevention.

“We just really need to, as I’ve said so often, prepare for the worst. And it may not be that we’re going to have to go the route people are saying,” Fauci told ABC. “We’ll make decisions based on the science and evidence as we always do.”