President Joe Biden has urged Americans not to panic about the new COVID-19 Omicron variant and says the United States is making contingency plans with pharmaceutical companies if new vaccines are needed.
Biden on Monday said the country would not go back to lockdowns to stop the spread of Omicron, and he would lay out his strategy on Thursday for combating the pandemic over the winter.
He urged people to get vaccinated, get boosters and wear masks.
"This variant is a cause for concern, not a cause for panic," Biden said in remarks at the White House following a meeting with his COVID-19 team.
"We're going to fight and beat this new variant," he said.
Omicron has prompted countries across the globe including the United States to limit travel from southern Africa, where the virus was first detected.
The World Health Organisation said Monday it carried a very high risk of infection surges, but said no deaths had yet been linked to the new variant.
Biden said it was inevitable Omicron cases would emerge in the United States. But White House spokesperson Jen Psaki said the variant should not cause Americans to change their holiday travel plans as long as they were vaccinated and wore masks.
Biden said he believed that existing vaccines would continue to protect against severe disease, but added his administration was working with vaccine makers Pfizer, Moderna and Johnson & Johnson to develop contingency plans.
Separately, the CDC said all vaccinated Americans aged 18 years and older should get a booster shot - a stronger recommendation than the one it issued last week , when the agency expanded booster eligibility to all adults but stopped short of saying that everybody should get them.
A US travel ban took effect earlier on Monday blocking most visitors from eight southern African nations from entering the country.
Biden said the travel restrictions were put in place to give the country time to get more people vaccinated.
Vaccine hesitancy in the United States and around the world has thwarted public health officials' efforts to get the pandemic under control.
Just 59 per cent of all Americans are fully vaccinated, although almost 70 per cent have at least one dose.
Nearly 782,000 people have died from COVID-19 in the United States, according to a Reuters tally
Australian Associated Press