(Updates with latest daily COVID hospitalizations; adds details, comments on vaccine preparations)
By Susan Heavey and Maria Caspani
WASHINGTON/NEW YORK, Dec 10 (Reuters) - A top coronavirus adviser to President-elect Joe Biden delivered a stern holiday message to Americans on Thursday - "no Christmas parties" - and warned they face a COVID-19 siege for weeks to come despite the latest moves toward U.S. government approval of a vaccine.
"The next three to six weeks at minimum ... are our COVID weeks," Dr. Michael Osterholm, a member of Biden's coronavirus advisory board, told CNN. "It won't end after that, but that is the period right now where we could have a surge upon a surge upon a surge."
Osterholm stressed that it would be several months before the nation sees widespread availability of vaccines, the first of which cleared a key U.S. regulatory hurdle on Thursday.
A panel of outside advisers to the U.S. Food and Drug Administration voted overwhelmingly to recommend emergency-use authorization of a vaccine developed by Pfizer Inc and its German partner, BioNTech SE.
FDA approval is expected within days, paving the way for a mass inoculation campaign unparalleled in U.S. history to be launched as early as next week. The advisory panel is due to review a second vaccine from Moderna Inc next week.
Preparations for the vaccine rollout were in full swing.
Delivery giants United Parcel Service and FedEx Corp stood by to ship millions of doses to distribution staging areas under contract with the federal government, giving top priority to the vaccines.
The Pfizer vaccines require storage in ulta-cold freezer units and must be prepared for injection and given quickly once thawed, posing special challenges to medical authorities.
"We only have six hours to actually use the vaccine," Dr. Stephen Dohi, chief pharmacist at the Los Angeles County USC Medical Center, said as he stood beside the hospital's newly purchased ultralow freezer.
Nevertheless, Osterholm said sizeable quantities of vaccines would not be available to the public at large before March or April. Healthcare workers and nursing home residents are likely to be designated as first in line for the shots.
Osterholm's blunt admonition came as COVID-19 caseloads soared higher, straining healthcare systems in cities and small towns across the country and leaving intensive care units in hundreds of hospitals at or near capacity.
He urged Americans to do their utmost to slow the contagion by limiting social interactions to members of their immediate households, and above all, "No Christmas parties."
"There is not a safe Christmas party in this country right now," he said. Health officials have voiced frustration that millions of Americans disregarded urgent appeals to limit travel and social gatherings over the recent Thanksgiving holiday, even as the pandemic was already raging unchecked.
DAILY DEATH TOLL EXCEEDS 9/11
On Wednesday the daily toll of COVID-19 deaths in the United States surpassed 3,000 for the first time, climbing to 3,253 fatalities. That exceeded the loss of life from the Sept. 11, 2001, attacks and pushed the total number of Americans killed by the virus since the start of the pandemic to more than 290,000.
A record 106,878 people were hospitalized with the highly contagious respiratory virus as of Thursday night, up at least 18% over the past two weeks, according to a Reuters tally of state-by-state data.
Pandemic hot zones abounded in rural areas and cities alike.
In California's San Joaquin Valley agricultural region, less than 2% of intensive care unit (ICU) beds remain unoccupied, the California Department of Public Health reported on Thursday. Available ICU capacity throughout the most populous U.S. state has fallen to just 7.7%.
Besides the staggering human cost, the pandemic has shattered the U.S. economy, forcing millions out of work as state and local authorities imposed sweeping restrictions on social and economic activities to curb the virus. Many Americans, however, have resisted public health directives to wear face coverings in public and avoid large crowds.
On Thursday, Virginia Governor Ralph Northam, a medical doctor, imposed a midnight-to-5 a.m. curfew among other measures that will kick in on Monday and last through at least Jan. 31.
Governor Mike DeWine of Ohio said he was extending his state's 10 p.m.-to-5 a.m. curfew until Jan. 2, and Pennsylvania Governor Tom Wolf, who tested positive for COVID-19 this week, announced new mitigation measures to take effect on Saturday.
Biden, who takes office on Jan. 20 after defeating President Donald Trump in last month's election, has set a goal of vaccinating 100 million people - about a third of the U.S. population - within the first 100 days of his administration.
Although the vaccine is seen as a pivotal weapon in ultimately vanquishing the pandemic, experts caution that its impact will be gradual due to initial supply limitations.
"It's not going to be like a light switch on and off," said Dr. Mark Mulligan, director of the NYU Langone Health Vaccine Center and a lead investigator for the Pfizer trials. "It's going to be more like a dimmer switch."
(Reporting by Susan Heavey, Maria Caspani, Sharon Bernstein, Norma Galeana, Lisa Shumaker, Manas Mishra and Julie Steenhuysen; Writing by Daniel Trotta and Steve Gorman; Editing by Bill Berkrot, Daniel Wallis and Gerry Doyle)
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