Fauci: Omicron ?raging through the world? and travel increases Covid risks

The Omicron variant of Covid-19 has "extraordinary spreading capabilities", the top US infectious diseases expert said on Sunday, and promises to bring a bleak winter as it continues "raging through the world".

Dr Anthony Fauci's warning came ahead of the busy holiday travel period, which he said would elevate the risk of infection even in vaccinated people.

In an interview with NBC's Meet the Press, Fauci, Joe Biden's chief medical adviser and head of the National Institute of Allergy and Infectious Diseases, urged Americans to get booster shots and wear masks.

He also appeared to attempt damage control over Vice-President Kamala Harris's contention that the Biden administration "didn't see" the Omicron or Delta variants coming.

Harris's comments on Friday were "taken out of context", Fauci insisted, and referred to the "extraordinary number of mutations" of Covid-19 rather than any lack of readiness.

"We were well prepared and expected that we were going to see variants," he said. "There's no doubt about that."

Fauci looked ahead to a scheduled national address by Biden on Tuesday, in which he said the president would "upscale" elements of the White House Covid winter plan.