WILMINGTON, Delaware — President-elect Joe Biden signaled strongly on Monday that fighting the raging pandemic will be the immediate priority of his new administration, an abrupt shift from President Donald Trump’s more unworried approach to the virus, as the nation surpassed 10 million COVID-19 cases.

Biden began with a direct appeal to all Americans to wear masks, a departure from Trump, who has mocked Biden and others who make a point of always wearing protective face coverings when around others. In an official move, the president-elect formed a coronavirus advisory board dominated by scientists and doctors, while Trump has had a falling out with the medical experts on his own virus task force.

The swift actions come at a critical moment in the U.S. effort to combat the coronavirus. Pharmaceutical giant Pfizer announced progress with its vaccine trial, helping send financial markets soaring. But surging caseloads, including new infections among leading figures in Trump’s administration, offered a fresh reminder that the nation is still in the grip of the worst pandemic in more than a century.

“The challenge before us right now is still immense and growing, and so is the need for bold action to fight this pandemic,” Biden said after being briefed on the virus. “We are still facing a dark winter.”

He called on Americans to separate politics from the virus and embrace mask-wearing.

“We could save tens of thousands of lives if everyone would just wear a mask for the next few months. Not Democratic or Republican lives, American lives,” Biden said. “Please, I implore you, wear a mask.”

Over the past two weeks, the number of confirmed COVID-19 cases has risen nearly 65%. The 7-day rolling average for daily new cases in the U.S. went from 66,294 on Oct. 25 to 108,736.7 on Sunday. In the past week, one of every 433 Americans was diagnosed with COVID-19, and hospitals in several states are running out of space and staff.

Biden noted the pandemic’s disproportionate toll on people of color as he called on Americans to separate politics from the virus and embrace mask-wearing. “Focusing on these communities is one of our priorities, not an afterthought,” Biden said.

Pfizer said Monday that its COVID-19 vaccine may be a remarkable 90% effective, based on early and incomplete test results. The drugmaker said it was on track to file an emergency use request with regulators later this month.

Vice President Mike Pence held a meeting of the White House coronavirus task force on Monday. He tweeted that Pfizer’s reported progress was “HUGE NEWS” and suggested it was the result of a “public-private partnership forged” by Trump.

In fact, Pfizer has funded all its own research. It has a contract to sell doses to the U.S. government if a vaccine is approved but has insisted on handling its own shipping.