The nation’s top infectious disease expert warned Sunday that the U.S. must act quickly to prevent a “dangerous” new surge of COVID-19 infections ahead of the holiday season – with many Americans planning to resume indoor gatherings, some for the first time since the start of the pandemic.

What You Need To Know

  • Dr. Anthony Fauci urged Americans who have not yet received the COVID-19 vaccine to do so on Sunday, warning that the U.S. is running out of time to prevent a dangerous “winter wave” of new COVID cases this holiday season

  • His remarks come as Europe continues to battle a crippling surge of new COVID-19 infections, prompting leaders to implement harsh new restrictions in hopes of avoiding hospital overcrowding and preventing another massive outbreak

  • In the U.S., new COVD-19 cases have begun to increase for the first time in weeks, with daily new cases surpassing 100,000 once again; Health experts worry this trend could be made exponentially worse by a strong surge in holiday travel

  • Roughly two in three Americans said their Thanksgiving gatherings this year will return to the same size as they were before the pandemic, according to a recent Monmouth University poll

Speaking on CNN’s State of the Union on Sunday, Dr. Anthony Fauci urged Americans who have not yet received the COVID-19 vaccine to do so, stressing that regular tests are not a substitute — especially as many Americans prepare to resume holiday travel this year and gather in-person with family and friends.

“We still have about 60 million people in this country who are eligible to be vaccinated who have not been, and that results in the dynamic of virus in the community that not only is dangerous and makes people who are unvaccinated vulnerable, but [one that] also spills over into the vaccinated people,” Fauci told CNN’s Dana Bash.

“We have a lot of virus circulating around. You can’t walk away from the data, and the data show that the cases are starting to go up, which is not unexpected when you get into a winter season,” he continued. “People start to go indoors more and we know that immunity does wane over time.”

Fauci’s remarks come as Europe continues to battle a crippling surge of new COVID-19 infections, prompting leaders to implement harsh new restrictions in hopes of avoiding hospital overcrowding and preventing another massive outbreak.

And in the U.S., new COVD-19 cases have begun to increase for the first time in weeks. The U.S. seven-day average of new cases has spiked by 36% this week compared to the previous week, and the number of daily new cases has surpassed 100,000 once again.

Health experts worry this trend could be made exponentially worse by a strong surge in holiday travel.

Roughly two in three Americans said their Thanksgiving gatherings this year will return to the same size as they were before the pandemic, according to a recent Monmouth University poll. And of those who plan to gather with people outside their household, 64% said they will not ask their guests whether they have received the COVID-19 vaccine. Just 27% said they will require their guests be vaccinated.

TSA is also expecting a surge of travelers that rival pre-pandemic levels. On Friday, it scanned more than 2.2 million people at airport security checkpoints — the highest one-day traveler volume since before the COVID-19 pandemic.

On ABC News’ “This Week,” Fauci noted that a key difference between this year and last year is the widespread availability of vaccines in the run-up to the holiday season, as well as the availability of booster shots, which on Friday were authorized by the FDA for all adults.

“The bottom line is: Get vaccinated if you’re not vaccinated, and boostered if you have been vaccinated,” Fauci said Sunday.

"We now have vaccines that are highly effective and clearly very safe, particularly now with the recent data showing that we can vaccinate children from 5 through 11," he continued. "There are 28 million children within that age category. If we started vaccinating them now, they'll be fully protected by Christmas."