Joe Biden's scientific advisers will meet with vaccine makers in coming days as the presidential transition remains stalled because of President Donald Trump's refusal to acknowledge that he lost the election. That delayed handoff to the next administration is especially problematic during a public health crisis, the government's top infectious disease expert said.

“Of course it would be better if we could start working with them,” said Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases who has been through many presidential transitions during 36 years of government service. He likened the process to runners passing on the baton in a relay race. “You don’t want to stop, he said.

The president-elect's outreach to the vaccine manufacturers comes as the coronavirus pandemic in the United States has entered perhaps its most dangerous phase. The seven-day rolling average for new daily cases stood at 145,400 on Saturday, according to data from Johns Hopkins University. That means the U.S. is adding about 1 million new cases a week, and deaths averaged 820 a day, a 33% increase in just two weeks.

FILE - In this Sept. 23, 2020 file photo, Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, listens during a Senate Senate Health, Education, Labor, and Pensions Committee Hearing on the federal government response to COVID-19 Capitol Hill in Washington.  Fauci is recommending masks at Thanksgiving gatherings if the coronavirus status of people is unknown.  (Graeme JenningsPool via AP)

FILE - In this Sept. 23, 2020 file photo, Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, listens during a Senate Senate Health, Education, Labor, and Pensions Committee Hearing on the federal government response to COVID-19 Capitol Hill in Washington. Fauci is recommending masks at Thanksgiving gatherings if the coronavirus status of people is unknown. (Graeme JenningsPool via AP)

"We’re going to start those consultations this week” said Biden's chief of staff, Ron Klain, citing Pfizer and other pharmaceutical companies.

Pfizer’s announcement that preliminary data indicate its vaccine is 90% effective lifted financial markets last week and gave many people worldwide hope that an end to the pandemic will be coming.

Around the country, hospitals report that doctors and nurses are being stretched to cope with rising numbers of hospitalized COVID-19 patients requiring special care. In some communities, hospitals have started limiting elective procedures in order to conserve resources.

Graphic shows how vaccine studies progress

Graphic shows how vaccine studies progress

Fauci stressed it won't be like flipping a switch to return to normal life when the first vaccine doses become available for high-risk groups, most likely next month. He said Americans will have to keep up preventive measures such as wearing masks, observing social distancing and frequently washing their hands well into next year.

“Everybody is sensitive to what we call ‘COVID fatigue,’ ” Fauci said. “But we've got to hang in there. We've got to hang together .. .because we can make it turn around.”

Fauci has been target of frequent complaints from Trump, and the president's supporters have called for him to be fired.

FILE - In this Sept. 23, 2020 file photo, Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, listens during a Senate Senate Health, Education, Labor, and Pensions Committee Hearing on the federal government response to COVID-19 Capitol Hill in Washington. Fauci says, Thursday, Nov. 11,  he doesn’t believe the United States will need to go into lockdown to fight the coronavirus if people double down on wearing masks and social distancing.(Graeme JenningsPool via AP, File)

FILE - In this Sept. 23, 2020 file photo, Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, listens during a Senate Senate Health, Education, Labor, and Pensions Committee Hearing on the federal government response to COVID-19 Capitol Hill in Washington. Fauci says, Thursday, Nov. 11, he doesn’t believe the United States will need to go into lockdown to fight the coronavirus if people double down on wearing masks and social distancing.(Graeme JenningsPool via AP, File)

Other vaccine makers are also in the final phase of testing their formulations, and Fauci said he expects those vaccines will also be highly effective.

The government has launched a program called “Operation Warp Speed,” backed by the White House, to quickly manufacture and distribute tens of millions of doses of vaccines. The shots will be free to Americans, and the goal is to have most people vaccinated by about this time next year. Many people will need two doses.

Initial access to the vaccine will be limited to high-priority groups such as hospital and nursing home workers.

Fauci was on CNN's “State of the Union” and Klain appeared on NBC's “Meet the Press.”