Anthony S. Fauci, the country’s leading infectious-disease expert, has said Americans can expect a return to normalcy by this fall. President Biden suggested on Tuesday that a better estimate for a return to the pre-pandemic normal would be Christmas.

Both goals come long after the end of July, when Biden promises there will be enough vaccine doses for every American, which is the benchmark that many people had believed would allow life to resume its normal course.

As the country approaches the one-year mark of the pandemic’s isolation and restrictions, the Biden administration is struggling to give precise, consistent answers to two key questions: When will the pandemic truly be behind us? And, short of that, when can children safely return to school?

Biden himself has blamed miscommunication for some of the inconsistency, but his administration — which has promised to use science and data as the basis for pivotal decisions — is also grappling with the fact that science and data don’t produce answers as tidy or linear as campaign promises.

For months, Biden has raised expectations that children would soon return to school, saying it is imperative for them and their parents alike. As a candidate, he set a goal that most schools would reopen within his first 100 days as president, and his press secretary, Jen Psaki, recently suggested that the White House considers schools to be open if students are in school at least one day a week.

But at a CNN town hall meeting Tuesday evening in Milwaukee, he clarified that he wants students back in school five days a week — while also specifying that his priority is students in grades K-8.

President Biden fielded questions at a televised town hall on Feb. 16, where he was asked about vaccines, immigration and domestic terrorism. (Drea Cornejo/The Washington Post)

He rejected the idea that one day a week was sufficient.

“No, that’s not true. That’s what was reported. That’s not true. There was a mistake in the communication,” Biden told host Anderson Cooper.

It was an attempt to add clarity to an increasingly murky issue at the intersection of safety, education and politics.

Hybrid schedules, in which students are in school buildings part of the time and at home other times, have emerged as a popular way for school districts to split the difference between being dangerously packed and completely closed. They let schools reduce the number of students inside buildings at any given time and allow for six feet of social distancing, hewing close to safety guidelines and reducing the risk of spreading the coronavirus.

While Biden pushed back against hybrid systems on CNN, guidelines issued by his own administration last week called for such an approach, if not fully remote education, for the vast majority of the country.

The Centers for Disease Control and Prevention said that if community transmission rates are high, as they are in the vast majority of the country, there should be no full-time, in-person school. Rather, the CDC said, schools can use a hybrid system — and only if the district is able to strictly implement sophisticated systems meant to prevent transmission.

“In areas of . . . high transmission, we have advocated for elementary schools to be in a hybrid-learning mode with reduced attendance because we really do believe that you need full, six feet of physical distancing at that level of transmission,” CDC Director Rochelle Walensky said Friday.

For high schools, Walensky added, “We are advocating for, perhaps, more virtual instruction,” with hybrid models in certain cases with strict protocols. So while the CDC is recommending fully remote or hybrid systems, Biden is not promoting either one.

Part of the challenge for the administration is that such decisions are made at the state and local level. But local officials often turn to the CDC for guidance, and the lack of clarity has frustrated many parents who have been forced to keep their children at home while still trying to perform their jobs.

Recent polls reflect the sensitivity of the school reopening issue. Fifty-eight percent of Americans approve of the way Biden is handling the pandemic overall, with 32 percent disapproving, according to a Quinnipiac University Poll released Wednesday — but the figure is far lower when it comes to school reopenings, with 42 percent approving of his performance and 38 percent disapproving.

Beyond that, Americans are divided on the basic question of how fast schools should reopen in the first place. In the poll, 47 percent said schools in their community were reopening at the right pace, 27 percent said not fast enough, and 18 percent said it was happening too fast.

The White House has also tiptoed around the thorny issue of teacher vaccinations. Early this month, Walensky said that teacher vaccination should be a priority for states but that it is not a prerequisite for reopening schools.

From the White House, Psaki pushed back. “Dr. Walensky spoke to this in her personal capacity,” Psaki said. “Obviously, she’s the head of the CDC, but we’re going to wait for the final guidance to come out so we can use that as a guide for schools around the country.”

Then, last week, the CDC guidance was issued and reaffirmed that teacher vaccination was not a prerequisite for opening schools.

Asked about the guidance Wednesday on NBC’s “Today” show, Vice President Harris declined to explicitly endorse it. “Teachers should be a priority,” she said several times. When pressed about teacher vaccinations in particular, she hedged, saying the CDC recommendations “are exactly that: recommendations.”

Later, she added: “We’re all really clear. Teachers should be a priority. Teachers should be a priority. Teachers are critical to our children’s development, they should be able to teach at a safe place and be able to expand the minds of our children.”

Then she pivoted to talking more about Biden’s $1.9 trillion “American Rescue Plan.”

Later Wednesday, Psaki clarified that the White House does subscribe to the CDC guidelines on teacher vaccination: “Neither the president nor the vice president believe that it should be a requirement” to reopen schools, she said.

Beyond schools, the administration’s messaging has also been less than clear about when the rest of Americans can return to normal, or what exactly normal means. Many people are looking forward to a time when they no longer have to wear masks or keep their distance from friends and loved ones.

The administration’s supporters say Biden’s lack of clarity on that reflects the reality — that scientists and public health experts themselves are not able to predict with any precision when normal life will return. Everything from the virulence of the coronavirus variants to unexpected logistical challenges in delivering vaccine doses to the resistance of some communities to get vaccinated could affect the timing of herd immunity, they say.

And as president, his allies add, Biden is seeking to balance the reassurance that he wants to offer a nation engaged in a critical battle with a desire not to overstate his certainty about when that victory will come.

Biden has greatly increased the supply of vaccine doses, putting in place arrangements that appear sufficient to produce enough to inoculate every American by July. But the conditions necessary for normalcy involve far more than supply.

And some of those social factors are not predictable.

While the two vaccines authorized in the United States are still believed to be effective against more transmissible and potentially more lethal virus variants now spreading in the country, they may offer less protection than hoped. And if the virus continues to mutate, people may need boosters or new vaccinations to maintain that protection.

In addition, the large numbers of people who remain hesitant about getting the shots make it unlikely the country will quickly reach herd immunity to stop the spread of the virus.

In the United States, some Black communities, who have suffered mistreatment and inequity at the hands of the medical establishment for decades, are expressing wariness of Biden’s vaccine push. Some cite concern at the rapid speed at which the vaccines were developed in the Trump era, worrying that safety corners may have been cut, although experts say that is not the case.

The federal government is making an effort to combat vaccine hesitancy, particularly among hard-hit minority populations, and to provide vaccination sites in communities with little access to medical facilities. But those efforts can take time.

And even the best-laid plans can be upended by something as simple as the weather.

Texas and other states, for example, are now digging out from under a deadly winter storm that knocked out power to millions — and threatens to slow or stall vaccination efforts for days or weeks.

CDC spokeswoman Kristen Nordlund said the government is projecting “widespread delays in coronavirus vaccine shipments due to the weather.”

But the schools carry particular political sensitivity for Biden, who must balance the desires of parents to send their children back to school, after a year of having to manage their education from home, with the fears of teachers and their unions.

Teachers unions were among the strongest supporters of Biden’s candidacy, and they remain big backers of his presidency and an important Democratic constituency. Their members are highly resistant to returning to school buildings across the country without significant safeguards and restrictions.

Last week, Chicago teachers ultimately decided to return to classrooms after agreeing on health and safety standards for school reopenings — but only after a long, sometimes bitter negotiation.

“Let me be clear — this plan is not what any of us deserve,” Jesse Sharkey, president of the union, said after the deal was announced. “The fact that [Chicago Public Schools] could not delay reopening a few short weeks to ramp up vaccinations and preparations in schools is a disgrace.”

Biden’s promise to open most schools by his 100th day in office, a date that falls in late April, was one of his most powerful pledges, a way to signal hope and progress in fighting the pandemic. But details have been hard to nail down.

Biden first clarified that the goal applied to only K-8 schools. Then Psaki clarified that “most” schools meant a majority — 51 percent. Psaki later said that hybrid programs — those in which students may be in school only one day a week — count as “open” toward the goal.

But if these are the measures, then the United States has probably already achieved Biden’s goal. According to data from calendar-tracking company Burbio, about 65 percent of students attend schools that offer full-time or part-time in-school options.