Dr. Anthony Fauci and White House coronavirus response coordinator Dr. Deborah Birx warned Tuesday that the U.S. hasn't yet seen the full impact of Thanksgiving gatherings.

“We have not yet seen the full blunt and the effect of the traveling and the congregating,” Fauci said at The Wall Street Journal's CEO Council summit .“That should be sometime probably next week, or a week and a half.”

"Then we're going to enter into the Christmas season, again, with more traveling and with more congregating at family and social gatherings. So we're in for a very challenging period," Fauci continued. "And the only way we're going to counter that is by a consistent uniform implementation and adherence to public health measures."

Fauci also said he’s accepted President-elect Joe Biden’s offer to become his chief medical adviser.

“I've already told the president-elect that I would gladly accept that responsibility. It really is very similar to what I'm doing now,” Fauci said.

ABC News' Anne Flaherty contributed to this report.

The University of Michigan said this Saturday's football game against Ohio State is now canceled due to "an increasing number of positive COVID-19 cases and student-athletes in quarantine over the past week."

"The number of positive tests has continued to trend in an upward direction over the last seven days," said Michigan's Athletic Director, Warde Manuel. "We have not been cleared to participate in practice at this time. Unfortunately, we will not be able to field a team due to COVID-19 positives and the associated quarantining required of close-contact individuals."

ABC News' Josh Hoyos contributed to this report.

Nearly 1.5 million children in the U.S. have tested positive for COVID-19 since the pandemic began, the American Academy of Pediatrics and the Children’s Hospital Association said in its weekly report.

During the week ending Dec. 3, there were 123,688 new cases of children with COVID-19, bringing the total number of U.S. children diagnosed to 1,460,905.

ABC News' Eric Strauss contributed to this report.

Scientists from the U.S. Food and Drug Administration on Tuesday appeared set to confirm that the Pfizer/BioNTech COVID-19 vaccine is safe and effective against the virus, according to documents released ahead of a crucial meeting on the vaccine this week.

According to a document prepared by FDA staff, government scientists plan to tell the advisory committee that the data is adequate to determine the vaccine is both safe and effective.

While that doesn't mean the FDA is prepared to authorize it just yet, the briefing materials suggest agency staff aren't warning of any last-minute issues.

"Safety data from approximately 38,000 participants [greater than or equal to] 16 years of age randomized 1:1 to vaccine or placebo with a median of 2 months of follow up after the second dose suggest a favorable safety profile, with no specific safety concerns identified that would preclude issuance of an EUA," the FDA wrote.

The report notes the most common reaction was a skin reaction at the injection site, followed by fatigue or headaches.

The FDA released data on the Pfizer/BioNTech vaccine trials and the agency's scientific analysis ahead of an advisory committee meeting on Thursday, when independent experts are set to discuss and vote on whether to recommend the vaccine be authorized for emergency use.

ABC News' Stephanie Ebbs and Anne Flaherty contributed to this report.

For the first time since the start of the coronavirus pandemic, the United States is reporting an average of nearly 2,200 deaths from the disease per day, according to an ABC News analysis of data collected and published by The COVID Tracking Project.

The national seven-day average of COVID-19 deaths per day day is currently 2,171. That figure has increased by 139% in the past month.

Last week, there were nearly 15,000 fatalities from the disease recorded nationwide, including five days where the daily death toll surpassed the 2,000 mark. That's roughly equivalent to 88 COVID-19 deaths reported each hour.

Meanwhile, the U.S. has reported over 100,000 new cases of COVID-19 every day for more than a month straight, including three consecutive days where the daily count topped 200,000.

Just in the last month, the national seven-day average of daily new cases has doubled, now averaging 191,736 -- the highest it has been since the beginning of the pandemic.

There were 1,018,657 cases recorded nationwide in the first five days of December. To put that in perspective, it took nearly 100 days from the first recorded COVID-19 case in the U.S. for the country to surpass 1 million confirmed cases.

Hospitalizations continue to surge to unprecedented levels, with over 101,000 patients currently hopitalized with COVID-19 across the country -- a new national record.

In the past two months, current hospitalizations have more than tripled, increasing by 223%.

ABC News' Benjamin Bell, Brian Hartman, Kim Soorin and Arielle Mitropoulos contributed to this report.