The number of new Covid-19 cases has plateaued at a "disturbingly high level," and the US is at risk from a new surge, Dr. Anthony Fauci warned on Wednesday.
Although off the highs of earlier this year, there were still more than 61,000 new cases reported on Wednesday, according to data from Johns Hopkins University. And the lack of continued significant decreases in infections is a concern, the director of the National Institute of Allergy and Infectious Diseases told CNN's Anderson Cooper, particularly given the spread of variants.
"It's almost a race between getting people vaccinated and this surge that seems to want to increase," Fauci said, noting Europe is experiencing a spike much like the one experts worry about for the US.
The US is vaccinating people quickly, with just over 33% of the population -- more than 109 million people -- having received at least one dose of the vaccine and all 50 states committed to opening vaccinations to all adults by April 19.
Those vaccines may be behind the decrease in Covid-19 fatalities, US Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said Wednesday.
But the pace of getting vaccines into the arms of Americans will need to keep increasing now that the virus variant first identified in the United Kingdom, known to be more transmissible and believed to be more deadly, is the most common strain in the US, Walensky said.
To fight the variant, Fauci urged Americans to get vaccinated and stick to preventative measures.
"Hang in there a bit longer," he said. "Now is not the time, as I've said so many times, to declare victory prematurely."
Cases skew younger
The country's daily rate of new coronavirus cases rose over most of the last four weeks. Part of that is due to the spread of B.1.1.7 and other concerning variants, Walensky said earlier this week.
The US has averaged more than 64,760 new coronavirus cases a day over the past week -- slightly lower than week prior, but still about 21% higher than two weeks ago, and more than 12% higher than four weeks ago, according to Johns Hopkins.
Recent infections have been skewing toward younger people, a factor Fauci said can be attributed in part to so many older people being vaccinated.
Fauci noted that more than 75% of people ages 65 years and older have received at least one shot of the Covid-19 vaccine in the US.
He said a number of factors are at play, including clusters of cases in daycares and school sports teams -- in which people are in close contact and sometimes aren't wearing masks -- and the B.1.1.7 variant.
"I think that is what is explaining these surges of cases in young individuals," he said.
As the cases trend toward younger Americans, many schools are expanding access to full in-person learning. About three-quarters of US public schools are open for full time in-person or hybrid learning.
Of the 4th graders in the nation, 39% are attending full-time in-person school and 29% of 8th graders, according to data released on Wednesday from the Department of Education's National Assessment of Educational Progress (NAEP).
Those students returning to school are not yet eligible for vaccines, though studies will hopefully show the effectiveness of vaccinations in children as young as six months in the coming months, Fauci said.
Until then, students under 16 should continue wearing masks, avoiding close contact and avoiding indoor settings, Fauci said.
Vaccine risks and benefits
As the US races to vaccinate people, experts and officials are contending with adverse reactions believed to be linked to some shots.
Operations were paused at Dick's Sporting Goods Park in Colorado on Wednesday after health officials reported that 11 people who received their vaccinations became ill.
Those patients experienced symptoms like nausea and dizziness and were transported to a local hospital for observation out of an abundance of caution, according to a news release from the Colorado State Joint Information Center.
Although the cases might sound concerning, state officials said they don't have reason to believe that people vaccinated at the center should be concerned.
"The state has no reason to believe that people who were vaccinated today at Dick's Sporting Goods Park should be concerned," state officials said.
"From what we know, today's side effects were consistent with what can be expected," said Scott Bookman, COVID-19 Incident Commander in the news release. "Getting a vaccine is far safer than getting severely sick with COVID-19."
CNN's Amanda Sealy, Ben Tinker, Lauren Mascarenhas, Betsy Klein, Elizabeth Stuart, Joe Sutton, Richard Greene and Schams Elwazer contributed to this report.