But the risk of explosive new strains, including a U.K. variant known as B.1.1.7, threatens to upend it all and leave Biden at the end of his first 100 days with a pandemic that has worsened, instead of improved. There’s concern among his team that the scope of the problem he’s inherited is far worse than anticipated, posing a political risk to Biden’s White House.If the new president fails to combat the virus effectively in his first few months, efforts to revive the economy or achieve other legislative priorities including an immigration overhaul or infrastructure development could be hamstrung. Biden’s aides privately allege that Trump’s administration dragged its heels in showing them details of the federal response and its data. Those concerns weren’t made public before the inauguration because Biden’s team believed it had to avoid publicly criticizing Trump’s team during the transition or risk being fully frozen out, people familiar with the matter said. The first days of the administration will be spent getting up to speed on the state of the response, one person said. A senior Trump administration official disputed that any information had been withheld from Biden’s transition, saying that since late November, there had been more than 300 meetings with Biden officials across the Department of Health and Human Services. The Trump administration also provided Biden’s team what the official said was unprecedented access to several “deliberative meetings,” as well as debriefings for some of them. On election day, the U.S. had never had a day with more than 100,000 new cases; since Nov. 5, it has never had a day with fewer than that. Osterholm predicted that the U.S. could see 400,000 to 500,000 daily new cases in 12 to 14 weeks, or roughly 100 days — five times higher than on election day.“When this B.1.1.7 takes off, it’s going to be hell,” Osterholm said. “That’s what they’re walking into right now. I hope I’m wrong. God, I hope I’m wrong.”In their planning, Biden advisers are also factoring in an exhausted, demoralized and bare-bones workforce in its departmental agencies, particularly at the Centers for Disease Control and Prevention. “Biden is coming in with entire offices gutted, or morale is so low,” said Kavita Patel, a nonresident fellow at the Brookings Institution, who served as director of policy for the Office of Intergovernmental Affairs and Public Engagement in Barack Obama’s administration. Vaccinations have fallen far short of targets set by President Donald Trump, who promised in September to have 100 million shots available by the end of the year. Just 16 million doses had been administered as of Wednesday, according to the Bloomberg vaccine tracker. The rising urgency is reflected in Biden’s own approach — during the transition he named a coronavirus advisory board, then a health team, and then a new batch of aides to bolster his response to the pandemic. Key positions remain unfilled, chiefly Food and Drug Administration commissioner. The vaccines work, though new strains threaten to degrade their efficacy. And one adviser wondered whether Biden’s public emphasis on mask-wearing and other sound public health practices would help, replacing Trump’s refusal to wear a mask and general scorn for recommended health guidelines.