US President-elect Joe Biden has picked California Attorney-General Xavier Becerra for secretary of health and human services as he prepares his administration’s response to the raging coronavirus pandemic and says he will name more cabinet nominees later this week.

Biden, who takes office on January 20, also chose Dr Rochelle Walensky, chief of infectious diseases at Massachusetts General Hospital in Boston, to run the US Centers for Disease Control and Prevention (CDC). Biden formally tapped Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, as his chief medical adviser on the virus.

Biden, who has already announced top nominees for his national security and economic teams, told reporters he expected to name his defence secretary on Friday and his nominee for attorney-general this week.

Jeff Zients, an economic adviser known for his managerial skills, was named coronavirus “czar” to oversee the response that will soon include an unprecedented operation to distribute hundreds of millions of doses of a new vaccine, co-ordinating efforts across multiple federal agencies.

Dr Celine Gounder, a member of Biden’s coronavirus advisory board, told CBS it still had not received a detailed plan for vaccine distribution from the outgoing administration of President Donald Trump.

“It’s not enough to acquire the doses of the vaccine, to purchase the doses. We also need to have a plan to distribute them all the way down to the level of the healthcare provider, the nurse,” Gounder said on This Morning.

More than 282,000 Americans have died from COVID-19, the disease caused by the virus, according to a Reuters tally. Authorities in California, the most populous state in the country with about 40 million residents, on Monday compelled much of the state to stay at home, the day after it reported a record 30,000-plus new cases.

Biden, a Democrat, has pressed ahead with the transition even as Trump, a Republican, refuses to concede the November 3 election and wages a foundering effort to overturn the results with unsubstantiated claims of fraud.

Dozens of Trump’s legal challenges have been rejected by the courts, the latest on Monday when judges in Detroit and Atlanta tossed bids to decertify Biden’s election victories in Michigan and Georgia.

In Georgia, Secretary of State Brad Raffensperger on Monday certified the state’s results, a statement said, after a third count confirmed Biden’s win. The electoral college will formalise results nationwide on December 14.

Raffensperger said continued debunked claims about voting fraud was “hurting our state”. Run-off elections on January 5 for Georgia’s two US Senate seats will determine which party controls the chamber.

Meanwhile, Trump’s personal lawyer Rudy Giuliani, who has led legal challenges in several states, was being treated in a Washington, DC hospital after testing positive for the virus.

The choice of of Becerra, 62, a Latino former congressman, comes as Biden faces pressure to ensure diversity in his cabinet appointments.