(CNN) - Millions of school-age children in the United States are still unvaccinated against Covid-19 as many prepare for a return to school.
A new CNN analysis finds that less than half of children and teens are fully vaccinated against Covid-19, and only a tenth have been boosted.
Many of the nation's largest school systems -- including Los Angeles Unified, City of Chicago, Miami-Dade County and Clark County in Nevada -- start school next month.
Covid-19 cases are rising across the United States once again, driven by the Omicron sub-variant BA.5, the most transmissible strain of the coronavirus yet.
More than 14 million children have tested positive for Covid-19 since the onset of the pandemic, according to available state reports; more than 311,000 of these cases have been added in the past four weeks, the American Academy of Pediatrics reported as of Thursday.
Federal health officials urge those who are eligible to stay up to date on Covid-19 vaccinations by getting boosted.
The US Centers for Disease Control and Prevention considers someone "fully vaccinated" if it has been at least two weeks since they had a second dose of the Moderna or Pfizer/BioNTech coronavirus vaccine.
They are "up to date" on their vaccinations if they've had the booster doses that they're eligible for.
Everyone 6 months and older is eligible for Covid-19 vaccination, and those 5 and older are eligible for a booster.
About 23.9 million 5- to 17-year-olds are fully vaccinated against Covid-19, according to data posted Thursday by the CDC.
That represents about 45% of that age group. About 22 million of them are eligible for a booster shot.
But only about 5 million young people, ages 5 to 17, have gotten a booster dose to fight Covid-19, according to CDC data.
That represents about 9.5% of that age group in the United States and 22.6% of those eligible who've already had their primary series.
That figure includes about 796,000 children ages 5 to 11 and 4.2 million adolescents ages 12 to 17 who have been boosted.
Daniel Bittman, superintendent of Independent School District 728 in Minnesota, said he expects his district's data aligns with what's happening at the national level.
His district, which serves students in five counties, starts its new school year the day after Labor Day.
"We have worked with the various counties and Department of Health to make vaccinations accessible for those who are interested in getting them, and we have worked diligently to remove barriers to make that possible and convenient for families," he said.
"We also provide opportunities for online learning from kindergarten through 12th grade. And that provides options for families who may be concerned about the spread of Covid at different times throughout the year."
Over the spring and summer, in preparing for the upcoming school year, many schools have hosted Covid-19 vaccine clinics for students.
"We've held vaccination clinics in different schools," said Gladys Cruz, district superintendent for Questar III in New York and president-elect of the School Superintendents Association.
"I would prefer in my schools that people get vaccinated, as possible," she said.
"But what I've seen throughout this pandemic is that for every person who wants to get vaccinated, there's another one that does not."
The uptake of Covid-19 booster shots among eligible school-age children and teens has been slow, mostly because many children still haven't completed their initial doses of vaccine.
According to survey results released Tuesday by the Kaiser Family Foundation, 37% of parents of children ages 5 to 11 and 28% of parents of a child 12 to 17 say they "definitely" will not get them vaccinated against Covid-19.
But most parents of vaccinated children in these age groups say their child has gotten or is likely to get a booster dose, according to the new KFF survey.
About 29% of parents of vaccinated children ages 12 to 17 say their teen has received a booster dose, and nearly half say they "definitely" or "probably" will do so, survey results show.
Among parents of vaccinated children ages 5 to 11, 20% say their child has received a booster dose, 31% say they will "definitely," and 24% say they "probably" will get one.