WASHINGTON (NewsNation Now) — President Joe Biden said Monday that the omicron variant of COVID-19 “is a cause for concern, not a cause for panic.”

Speaking from the White House Monday morning, Biden urged Americans to get vaccinated and get their booster shot.

“Do not wait. Go get your booster if it’s time for you to do so," Biden said. "And if you are not vaccinated, now is the time to go get vaccinated and to bring your children to go get vaccinated.”

The United States began restricting travel to at least eight African countries Monday as the reports of the variant popping up in countries around the world emerged.

It’s not clear where the new variant first appeared, but scientists in South Africa alerted the World Health Organization, and it has now been seen in travelers arriving in several countries, from Australia to Israel to the Netherlands.

“We’ll fight this variant with scientific and knowledgeable actions and speed, not chaos and confusion,” Biden said. “We have more tools today to fight the variant than we ever had before, from vaccines to boosters, to vaccines for children."

The nation's top infectious disease expert, Dr. Anthony Fauci, told Biden Sunday during a task force meeting that it would take two more weeks to learn how transmissible and how severe the omicron variant really is.

This comes after Fauci said he would not be surprised if the omicron variant was already in the United States.

"We have not detected it yet, but when you have a virus that is showing this degree of transmissibility and you’re already having travel-related cases that they’ve noted in Israel and Belgium and other places, when you have a virus like this, it almost invariably is ultimately going to go essentially all over,” Fauci said.

Both Pfizer and Moderna said they are monitoring the variant and expect more information about the current vaccines' effectiveness in the coming weeks.

Pfizer said it could adjust its vaccine to be more effective against this variant “within six weeks and ship initial batches within 100 days” if needed.

Moderna's Chief Medical Officer Paul Burton said to the BBC Sunday that the vaccine maker could introduce a reformulated vaccine against the omicron variant next year.

“We should know about the ability of the current vaccine to provide protection in the next couple of weeks, but the remarkable thing about the MRNA vaccines, Moderna platform is that we can move very fast,” Burton said.

This story is developing. Refresh for updates.