Children’s Hospital of Philadelphia announced Wednesday that it will open 10 vaccine clinics in Pennsylvania and New Jersey for their primary care patients, a day after the government gave final clearance to Pfizer’s two-dose COVID-19 vaccine for children ages 5 to 11.

The CDC estimates there are 28 million children in the United States in that age group, and Philadelphia health officials say there’s no time to lose in this critical step toward a return to normalcy.

Yet smaller patients require a different approach that has an already-strained health-care workforce scrambling. Young children will receive a smaller dose with smaller needles and, in many cases, will have appointments at clinics and offices dedicated to pediatric care — separate from the clinics many health systems are already running for adults and children age 12 and older.

“The task at hand of vaccinating 28 million children all at once is a fundamental mismatch with the way we deliver health care,” said Susan Coffin, an attending physician in the division of infectious disease at CHOP. “I don’t think we have a model that tells us this is the number of staff we need to vaccinate this many children in order to reach our goal of vaccinating 28 million children as soon as possible.”

» READ MORE: What parents need to know about the COVID-19 vaccine for younger kids.

The Philadelphia Department of Public Health has ordered 20,000 doses of the vaccine for children aged 5 to 11, which will be sent directly to the city’s health partners, said Cheryl Bettigole, acting health commissioner. Young children should be able to get the vaccine at the city-run community clinics, most pharmacies and health centers, though appointments may be limited until more shipments of the vaccine arrive.

“For the first few days it may be difficult to find pediatric vaccine,” Bettigole said. “We are all going to need a little patience.”

At the new Dr. Ala Stanford Center for Health Equity, marking its first day of seeing patients Wednesday, Stanford announced on Twitter that a 9-year-old got his COVID-19 shot alongside his parents, who received their boosters.

CHOP will have vaccine clinics in West Philadelphia, South Philadelphia, and Cobbs Creek, as well as others in the city’s Pennsylvania and South Jersey suburbs. The hospital has not yet released specific locations or opening days for the clinics, but Coffin said administrators considered where children may have less access to the vaccine through other sources, such as pharmacies and at routine pediatrician appointments.

Only CHOP primary care patients will be able to get a vaccine at one of the clinics. CHOP has about 100,000 primary care patients between ages 5 and 11, and hopes to vaccinate half of them over the next three months.

Meanwhile, doctors at St. Christopher’s Hospital for Children are concerned about staff shortages. Already the hospital had to cancel its annual flu vaccine clinic because there were not enough nurses and medical assistants to staff it, said Daniel Taylor, medical director of the outpatient center at St. Christopher’s.

“Demand is good. Supply is good. We’re going to have enough vaccine,” he said. “But ... there isn’t right now a good supply of support staff around the country to give the vaccine.”

Many health officials are urging parents to get their children vaccinated against flu and COVID-19 at the same time, because after last year’s lockdowns, a tougher flu season is expected.

The coronavirus pandemic accelerated an existing shortage of nurses, with many people leaving the workforce citing burnout after 20 months on the pandemic’s front lines.

Nurses play an integral and varied role in health systems, providing day-to-day care for hospitalized patients, assisting doctors and physician assistants, and administering vaccines.

“If we don’t figure this out, there’s going to be continued cases of COVID-19, continued cases of kids bringing it home to multigenerational households with people who may not be vaccinated,” Taylor said.

Temple Health is also feeling the strain of the worker shortage. The hospital has about 200 open positions, though it has been able to hire in critical areas, like nursing, which has helped keep vaccination efforts on track, said Tony Reed, chief medical officer for Temple University Health System.

Children 12 and up are being vaccinated at Temple’s adult vaccine clinics, but the health system plans to have its pediatrician offices handle younger patients.

“We have a saying in medicine that kids are not just small adults. It really is about helping the child feel comfortable, so they’re not traumatized by the needle,” Reed said.

In the Poconos, St. Luke’s University Health System is operating clinics dedicated to 5- to 11-year-olds during evenings and weekends. The children’s clinics are being run almost exclusively by doctors, nurses, and medical assistants within the health system who are volunteering their time after a regular workday “because they understand the importance of being able to provide the vaccine to this age group,” said Dianne Jacobetz, a pediatrician at St. Luke’s University Health Network.

“We’re feeling that pinch of not having enough staff,” she said. “But we are managing.”