Many parts of the country are seeing peak infections, with record numbers of people in hospital, with some experts blaming travel by millions over the recent Thanksgiving holiday.
What has Biden said?
The president-elect was attending a press conference in Delaware during which he introduced California Attorney General Xavier Becerra as his nomination for health secretary and his choice of Rochelle Walensky as head of the Centers for Disease Control and Prevention (CDC).
Mr Biden said: “My first 100 days won’t end the Covid-19 virus. I can’t promise that. But we did not get into this mess quickly. We’re not going to get out of it quickly.”
He said in the first “100 days we can change the course of the disease and change life in America for the better”.
But he warned that the coronavirus efforts could “slow and stall” if Congress did not conclude bipartisan talks and urgently come up with funding.
Getting children back to school would also be a priority, he said.
Among Mr Biden’s other aides will be Dr Anthony Fauci as chief Covid medical adviser. The infectious diseases expert also advised the Trump team – and often fell foul of the president for his views.
What happened at the White House?
It was mainly a celebration of Operation Warp Speed’s efforts to get a vaccine to the American people. Any rollout of the largest vaccination programme in US history will be carried out by the Biden team.
President Trump said of the expected vaccine approvals: “They say it’s somewhat of a miracle and I think that’s true.”
He added: “Every American who wants the vaccine will be able to get the vaccine and we think by spring we’re going to be in a position nobody would have believed possible just a few months ago.”
The Trump administration hopes to vaccinate as many as 24 million people by mid-January.
The president also signed an executive order aimed at ensuring that Americans had first priority in receiving doses – a move that appeared to follow his longstanding America First policy.
But how it will affect contracts that US companies have already signed with other countries remains unclear.
Mr Trump’s administration did sign up for an initial 100 million doses of the Pfizer/BioNTech vaccine but a member of the Pfizer board said the chance to buy more was turned down a number of times and more than the 100 million might not be available until June.