President Joe Biden has declared the current coronavirus surge a "pandemic of the unvaccinated."

But as the United States confronts its worst moment of the pandemic since the winter, there is a group of 48 million people who do not have the option of getting a vaccine: children younger than 12.

Because a vaccine is not yet authorized for young children and may not be for some time, their families are left in a particularly difficult position heading into this school year.

"Waiting for a vaccine for the under-12 set has started to feel like waiting for Godot," said Dana Gilbert, 49, of Minneapolis.

Her 11-year-old son was born prematurely and has special needs, and a family doctor advised that he not return to school in person until a vaccine is available.

She had hoped that might happen by now. Instead, she is scrambling to find a tutor.

Her plan is to wait out the clock: Keep him at home until a vaccine is authorized for emergency use or until he turns 12 next year, whichever comes first.

Polls show that a considerable number of parents do not intend to get their children vaccinated even when shots become available. The Kaiser Family Foundation found that 25%-30% of parents with younger children would "definitely not" get them vaccinated. A Gallup poll found that 46% do not plan to do so.

But millions of other families are in anxious limbo, waiting for a vaccine as the delta variant leads to a swell of new cases, including in children.

The timeline for a vaccine for children younger than 12 — initially expected by this fall — appears to have slowed as officials consider safety, effectiveness and dosage. Dr. Anthony Fauci, the nation's top infectious disease expert, recently indicated that a vaccine could become available to young children "hopefully by the mid, late fall and early winter." Shots for children ages 5-11 are expected first; children as young as 6 months may have to wait longer.

In interviews, many parents of children younger than 12 described feeling increasingly desperate, angry and backed into a corner as they reluctantly send their children into the classroom this fall — or resort to drastic actions to keep them safe.

Others are less worried but equally frustrated as they head into another school year marked by pandemic rules. In some cases, mandates are being applied most stringently to young children not eligible for a vaccine.

"It doesn't feel like there are any good options at this point," said Adina Ellis, 45, who tossed and turned in bed for hours the night before school started this week in Washington, D.C., racked with indecision about whether to send her 6-year-old son, Cassius.

Ellis lost her father to COVID-19 last year and had been among a group of parents calling for the mayor to allow remote learning. But like some other large cities, Washington is requiring nearly all students to attend in person this year.

On the first day of school, Ellis rose before dawn, sat on her front porch with her husband and made a "game-time decision," she said, to drop her son off at school. Watching him walk up the steps, carrying a Hot Wheels backpack, some part of her became resigned to the possibility that he may get infected.

"That thought will haunt me for as long as he's going to school unvaccinated," she said.

The data on coronavirus cases in children is imperfect, but by most accounts, serious illness has been rare.

Throughout the pandemic, fewer than 2 in 100 COVID-19 cases in children have resulted in hospitalization, and fewer than 3 in 10,000 cases have resulted in death, according to state-level data analyzed by the American Academy of Pediatrics. Because many asymptomatic cases in children may go undetected, the risk could be lower.

But the delta variant has added a new wrinkle that is not yet fully understood.

More children are now getting seriously sick as hospitals fill up with coronavirus patients, by and large unvaccinated. Delta is roughly twice as infectious as the original virus, leading to more overall infections, and researchers are seeking to understand whether it is also more severe. One recent study found that delta is more likely to cause hospitalizations. Some children have also developed debilitating long-term cases of COVID, even after initially mild or asymptomatic infections.

That uncertainty has left parents to make their own risk calculations, often coming to vastly different conclusions.

Mike Mulder, 41, is more worried about his children's risk from a vaccine than from COVID-19 itself.

"A lot of people like to paint people like us as anti-vax, but we're not," said Mulder, who lives in San Luis Obispo County, California, and is part of a parent group that pushed for in-person learning and mask freedom during the pandemic.

He said he had vaccinated his six children for other diseases but was not yet ready to do so for the coronavirus because of the lack of long-term studies.

"We are just concerned, like so many other people, that it's so new," he said.

Todd Newlin, 40, of Ramsey, Minnesota, near Minneapolis, said that he and his wife were vaccinated and planned to vaccinate their children, ages 4, 9 and 11, when a shot became available. He is open to the vaccines, in part, because he wants his family to be able to travel, go unmasked and live life as normally as possible.

But with cases rising, his district enacted a mask requirement for kindergarten through sixth grade. Older students — who have the option to be vaccinated — do not have the same requirement.

He said he would reluctantly follow the local mandate, although he views the health risks for children who get the coronavirus as relatively low.

"I'm not going to teach my kids to live in fear," he said.

At least 450 children have died from COVID-19, according to the Centers for Disease Control and Prevention, out of more than 640,000 people who have died in the United States.

Alexandra Simbaña looks at the same risks and is gripped with fear.

"When people say, 'Oh, a small percentage of children will get fatally sick,' that is not comforting when you have been to the dark side of the moon," said Simbaña, 42, of Washington, D.C., who was hospitalized for COVID-19 last year and is still suffering from health problems.

She kept her 9-year-old daughter home this week rather than send her into a classroom.

"No," she said, "that 1% could be my child."

And then there is a simple practicality that often cuts through it all: child care.

"If I had an option and I could keep them at home and keep the lights on and feed them, it would be a no-brainer," said Isis Spann, 32, of Moncks Corner, South Carolina, an education coach who works with families to teach elementary-age children at home. "But it just doesn't work out for our family dynamic that way."

She is cautiously sending her four children to school in person this fall.

The lack of a vaccine for young children has also helped fuel anxiety over masking.

In Texas, where school mask mandates are banned, Jason Helms, 39, of Fort Worth said he became alarmed on the first day of school when his 6-year-old daughter's teacher was not wearing a mask.

"We went home, and we laid on the floor, and we cried," Helms said.

He was particularly concerned about exposing his 3-year-old daughter, who is vulnerable to respiratory problems.

His family felt they had little choice but to move.

His wife, Meaghan Helms, took the children to live with her parents in North Carolina, where the family believed they would have more access to children's hospital beds and where their 6-year-old is attending a school that requires masks. Jason Helms has remained in Fort Worth for work.

Federal officials are facing intensifying pressure to accelerate emergency use authorization for a vaccine, including from the American Academy of Pediatrics, which has urged authorization "as soon as possible."

Tera Long, 39, of Sallisaw, Oklahoma, was so worried about her state's ban on mask mandates that on the second day of school, she signed up her daughter, 10, for a clinical trial for a vaccine.

"I'm ready," she said.

Two coronavirus vaccine makers, Pfizer-BioNTech and Moderna, recently expanded the size of their studies in children ages 5-11, a precautionary measure intended to detect rare side effects, including heart inflammation problems.

Pfizer has said it may be able to submit data to the Food and Drug Administration this month, but any timetable for authorization is uncertain.

For the time being, many parents are just trying to get by.

Juliet Muller, 46, sent her 9-year-old daughter back to school in Chicago this week, hoping for the best. If her daughter stays healthy, she said, the benefits of learning in person and being around other children will be worth it. Still, she cannot help thinking about worst-case scenarios.

"You are just juggling chain saws," she said. "And you are hoping to catch it right."

This article originally appeared in The New York Times.