NEW YORK — U.S. deaths from COVID-19 are falling again as the nation continues to recover from the devastating winter surge, a trend that experts are cautiously hopeful will accelerate as more vulnerable people are vaccinated.

While new coronavirus infections and hospitalizations have plummeted, the decline in deaths from a January peak of about 4,500 hasn’t been quite as steep. But, now, after weeks of hovering around 2,000 daily deaths, that figure has dropped to about 1,400 U.S. lives lost each day to coronavirus.

“I am encouraged by these data but we must remain vigilant,” Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said at Friday’s White House briefing.

Public health experts say it’s too soon to say, definitively, what’s driving declines since the surge — but they suspect a post-holiday drop in traveling and indoor gatherings, widespread mask wearing and the vaccine rollout have all contributed.

“We’re moving in the right direction,” said Harvard Medical School researcher Jagpreet Chhatwal. “I think a message of optimism is fair.”

Walensky and others worry that a pandemic-weary public will let down its guard too soon. And they’re monitoring the spread of worrisome new versions of the virus.

“We’re all desperate to get done with this,” said Jeff Shaman, who studies infectious disease at Columbia University. “We’re not in a place where it’s safe as of yet.”

Health care workers say they’ve seen it happen before — a crushing wave of illness and death, momentary relief from a drop in COVID-19 cases, and then, another deadly surge. About 531,000 Americans have died since the pandemic began a year ago.

“Every time you thought you had an end, the number of cases went up,” said Dr. Mark Rosenberg, head of emergency medicine at St. Joseph’s Health in Paterson, New Jersey.

For now, most forecasts show coronavirus deaths falling further in coming weeks as more people get vaccines. More than 100 million doses have been given out since December, and the pace is picking up.

“We expect it to continue to drive those deaths down even more,” said Johns Hopkins infectious disease expert Justin Lessler.

As of this week, 62 percent of those 65 and older have gotten at least one dose, according to the CDC. That’s the age group that’s been hit the hardest and still accounts for the vast majority of COVID-19 deaths in the U.S.

Increasingly better treatments for severe COVID-19 will also continue to help, doctors say.

“All of these things are coming together to put a dent in the problem,” said Dr. Lewis Nelson, an emergency medicine specialist at Rutgers New Jersey Medical School.

The tally of coronavirus deaths often lags behind new infections and hospitalizations, since it can take a long time for someone to become seriously ill and die after contracting the virus. It can also take weeks for deaths to be added to the national count.

“There’s sort of a longer tail, sadly, on death and dying from COVID-19,” said Boston College public health expert Dr, Philip J. Landrigan.

That’s what happened in the case of Teresa Ciappa, 73, of Amherst, New York, who developed a terrible cough and fever around Thanksgiving. She was admitted to the hospital soon after and died in early January of complications from COVID-19.

“Week after week she just declined and declined,” said her daughter, Michelle Ciappa, who lives in Columbus, Ohio.

Her family was there when she was taken off of a ventilator.

“We watched her take her last breath and that was it,” Michelle Ciappa said. “I wish people would be patient and take this more seriously.”

If states continue lifting restrictions, health experts warn, we could see another deadly wave of illnesses.

On Monday, Wyoming became the latest state in a growing list — including Texas, Mississippi, North Dakota, Iowa, Montana and Alabama — that has pulled mask requirements or plan to do so soon. Governors across the country have also eased restrictions on how many customers can be allowed in bars, restaurants, gyms and movie theaters.

“They’re not taking a slow measured approach. They’re flipping a switch,” Lessler said. “There is the very real possibility of big resurgences.”

Experts also worry about unchecked spread of mutated versions of the coronavirus that spread easier and could blunt the effectiveness of certain treatments or vaccines.

“It’s still a race against time,” said Jaline Gerardin, who studies COVID-19 trends at Northwestern University. “The fear is we won’t catch something when we should.”

Rosenberg, the ER doctor, said he hopes the public will be encouraged by the pandemic’s downward trend to keep wearing masks, washing their hands and staying a safe distance from others.

“We know what worked,” he said. “If we’re saying we’re in the last phase of the battle, don’t put your weapons away yet.”

AP writers Thalia Beaty in New York and John Seewer in Toledo, Ohio, contributed to this report.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.