There's good reason to be optimistic about where the U.S. could be by summer as COVID-19 vaccinations accelerate.

But right now, there are several threats looming. And the country is at a crossroads.

"On the one hand we are getting vaccines out at a record pace, but on the other hand we have these variants. We also know surges have occurred after spring break and after holidays before. So what happens now is really up to us," emergency physician Dr. Leana Wen told CNN on Sunday.

Centers for Disease Control and Prevention data shows more than 4,800 cases of coronavirus variants first spotted in the UK, South Africa and Brazil have been reported in the US. The true number of cases is likely higher -- this number only represents cases that have been spotted with the help of genomic sequencing, the agency has said.

"The best way that we can avoid any threat from variants is do two things," Dr. Anthony Fauci told CNN Sunday. "Get as many people vaccinated as quickly as we possibly can and to continue with the public health measures until we get this broad umbrella of protection over society that the level of infection is very low."

That means the U.S. shouldn't be easing restrictions before daily COVID-19 case numbers fall below 10,000 and "maybe even considerably less than that," Fauci has previously said.

But a growing list of governors have recently announced eased restrictions. And U.S. infection levels are anything but low as variants circulate. An average of more than 53,000 COVID-19 cases and more than 1,350 deaths were reported daily over the past week.

The decline of cases that officials reported earlier this year now seems to have leveled off, which has experts worried.

"Based on our previous experience in this country and in other countries, when you see a plateau it predicts another surge," infectious disease specialist and epidemiologist Dr. Celine Gounder told CNN Sunday. "And we have these new variants that are also very much potentially fueling a more severe surge."

 

MEANWHILE, TRAVEL HITS PANDEMIC RECORDS

 

Spring break -- which has kicked off across the country -- could be a perfect storm for spreading variants.

Already, crowds of vacationers have begun filling Florida beaches -- and they could unknowingly bring back the virus with them when they return home, one expert has previously warned.

In Miami Beach, Mayor Dan Gelber said over the weekend local officials are seeing "too much spring break activity."

"We've got a problem with too many people coming here," the mayor said. "We've got a problem with too many people coming here to let loose."

Meanwhile, air travel across the country is hitting pandemic records.

More than 1.3 million people were screened at airports on Friday -- the highest number since March 15, 2020, according to the Transportation Security Administration.

More than 1.2 million people were screened Saturday, according to TSA spokesperson Lisa Farbstein. That's about double the number of people who were screened on February 9, Farbstein said in a tweet.

"It was the 8th day this month that throughput has exceeded (one million). If you plan to travel, please wear a mask," Farbstein added.

 

GOOD NEWS FOR VACCINES

 

While many Americans push for a return to normalcy with warmer weather on the horizon, US officials are working to get as many shots into arms as quickly as possible.

So far, more than 69.7 million people have gotten at least one dose of a COVID-19 vaccine. More than 37.4 million are fully vaccinated -- roughly 11.3% of the U.S. population.

On Sunday, Dr. Scott Gottlieb, former Food and Drug Administration commissioner and current Pfizer board member, offered more encouraging news.

"All of the evidence across all the vaccines now is pointing in the direction that these vaccines reduce asymptomatic infection and reduce transmission," he told CBS.

"If that's the case, the vaccine creates what we call 'dead-end hosts' -- a lot of dead-end hosts -- meaning people will no longer be able to transmit the infection," Gottlieb added.

Last week, the CDC released its first set of guidelines for fully vaccinated people -- guidance the agency and other officials have said will evolve as more Americans are vaccinated and more data becomes available.

"What we've seen was the first installment of what you can do if you're vaccinated ... what you can do in the home setting, with the vaccinated people together or vaccinated people with an unvaccinated person," Fauci told CNN Sunday.

"You're going to see very soon similar types of guidelines for the American public, with regard to travel, the workplace, all kinds of different things," he added. "You will imminently be seeing those types of guidelines coming out."

 

POLITICAL DIVIDE OVER VACCINATIONS

 

Health experts have estimated that somewhere between 70% to 85% of the U.S. population must be vaccinated in order for the country to reach herd immunity against COVID-19. But major challenges remain, CDC Director Dr. Rochelle Walensky said last week, including "constrained vaccine supply, ongoing vaccine hesitancy and increasing myths and disinformation related to COVID-19 vaccines."

Another challenge: a political divide among Americans planning to get a shot.

A CNN poll conducted by SSRS, which was released on Thursday, shows that while 92% of Democrats say they have gotten a dose of the vaccine or plan to get one, that falls to 50% among Republicans.

It's a finding Arkansas Gov. Asa Hutchinson called "troubling."

In Georgia, Gov. Brian Kemp said in a news conference late last week the state is seeing vaccine hesitancy from White Republicans in several communities.

Another poll, by NPR/PBS NewsHour/Marist, found that nearly half -- 47% -- of people who supported President Donald Trump in the 2020 election said they would not get a COVID-19 vaccine if it became available to them, while only about 10% of people who supported President Joe Biden said they wouldn't get a vaccine.

Fauci said on "Fox News Sunday" he thought that Trump telling Republicans to get vaccinated "would make all the difference in the world."

"He's a very widely popular person among Republicans. If he came out and said, 'Go and get vaccinated, it's really important for your health, the health of your family and the health of the country,' it seems absolutely inevitable that the vast majority of people who are his close followers would listen to him," Fauci said.