Americans urged to get vaccinated as first Omicron variant case detected in U.S.

Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, speaks during a hearing of Senate Health, Education, Labor and Pensions Committee in Washington, D.C., the United States, on July 20, 2021. (J. Scott Applewhite/Pool via Xinhua)

"We know what we need to do to protect people. Get vaccinated, if you're not already vaccinated. Get boosted if you've been vaccinated for more than six months with an mRNA or two months with [Johnson &Johnson]," White House chief medical adviser Anthony Fauci said.

WASHINGTON, Dec. 1 (Xinhua) -- White House chief medical adviser Anthony Fauci on Wednesday urged Americans to get vaccinated or boosted against COVID-19 as the first U.S. case of Omicron variant was found in California.

"We know what we need to do to protect people. Get vaccinated, if you're not already vaccinated. Get boosted if you've been vaccinated for more than six months with an mRNA or two months with [Johnson &Johnson]," Fauci told reporters in a news conference at the White House.

As of Nov. 30, 197.1 million people, or 60 percent of the U.S. population, have been fully vaccinated. And 41.1 million received a booster shot, according to data from the U.S. Centers for Disease Control and Prevention (CDC).

As Fauci spoke, California's health officials announced in a statement that a fully vaccinated traveler who returned to the state from South Africa on Nov. 22 was tested positive with Omicron variant.

"We knew that it was just a matter of time," Fauci said. "The individual is self-quarantining and all close contacts have been contacted and all close contacts thus far have tested negative."

Fauci said the person was vaccinated but had not received a booster shot and was experiencing "mild symptoms."

There are currently no other cases the CDC is investigating as Omicron-linked, said Fauci.

White House press secretary Jen Psaki told reporters that President Joe Biden has been briefed on the Omicron variant, noting that he meets with his medical team on a daily basis.

People wait at a mobile COVID-19 vaccination site in the Brooklyn borough of New York, the United States, Nov. 19, 2021. (Photo by Michael Nagle/Xinhua)

On Monday, Biden called the variant "a cause for concern, not a cause for panic," saying "we'll have to face this new threat just as we face those who have come before it."

The Biden administration moved in late November to restrict travel from South Africa and seven other southern African countries where the Omicron variant was identified.

According to media reports, the CDC was moving to tighten U.S. testing rules for travelers from overseas, including requiring a test for all travelers within a day of boarding a flight to the United States regardless of vaccination status. It was also considering mandating post-arrival testing.

Officials have directed airlines carrying passengers that have been to certain southern African nations to share those passengers' contact information with health authorities, reported CNN on Wednesday, citing CDC spokesperson Kristen Nordlund.

The World Health Organization has warned that the risk posed by the Omicron variant is "very high." More than a dozen countries have detected the variant.