Updated: 12 AUG 21 12:35 ET

By Madeline Holcombe and Theresa Waldrop, CNN

(CNN) -- More children are being hospitalized with Covid-19 as health systems struggle to cope with a surge in new patients and officials race to expand vaccine protection.

The seven-day average number of children reported hospitalized with Covid-19 jumped almost 30% to a new peak of 239 in the week ending August 9. That number is up from the 184 children reported the previous week, according to data from the US Centers for Disease Control and Prevention.

Evaluating vaccines for children under 12 is now a top priority for the US Food and Drug Administration, and it is possible that doses could become available to them by the end of the year.

"Make no mistake, the FDA will move quickly on this because they recognize what's at stake. It's the health of our children, and there's really nothing more important than that," Surgeon General Dr. Vivek Murthy told CNN's Wolf Blitzer.

The urgency to get more of the population protected by vaccines is growing, said CNN medical analyst Dr. Leana Wen, who noted the worrying spread of the more transmissible Delta variant, adults being less cautious about protection and more children being admitted to the hospital.

"We have the more contagious Delta variant, we have surges and we have so many adults letting down their guard, not wearing masks, not getting vaccinated," Wen told CNN's Wolf Blitzer on Tuesday.

"That's contributing to this really dangerous environment for children."

And in the next 48 hours, the FDA is expected to announce it is authorizing a third vaccine dose to help some people who are immunocompromised, according to a source familiar with the discussions.

For people with compromised immune systems, including some cancer patients, those taking medications that suppress the immune system and organ transplant recipients, the two doses of mRNA vaccine or a single dose of Johnson & Johnson may not be enough to develop adequate antibodies, Murthy said.

These people "really never got a good response to begin with," from their immunizations, so the extra dose is "more of getting them up to what they hopefully had gotten the first time around, but we know because of their immune compromise, they didn't," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said on NBC's "Today" show on Thursday.

More than 60% of the adults in the US are fully vaccinated, according to data from the CDC. But an ensemble forecast published Wednesday by the CDC projects that new hospitalizations and deaths will likely increase over the next four weeks.

The new school year already upended

For many students, the new school year has just begun -- and the fresh surge in cases is already causing disruption.

In Mississippi, more than 4,400 students are quarantining after being exposed to Covid-19 during the week of August 2, according to data from the state's department of health.

In Lamar County, Mississippi, several schools were forced to switch to virtual learning to combat rising cases. Superintendent Steven Hampton proposed the hybrid schedule during a board meeting on Monday, saying while he believes face-to-face learning is best, a hybrid model would help avoid having all of the schools be virtual.

"Face-to-face learning is the best way for our children to learn but I just don't feel like it's safe," Hampton said.

In Georgia, all 14 cities within the Fulton County Schools jurisdiction are exceeding the qualifications for "High Community Spread," and the requirement to wear a mask indoors has been extended to all schools within the district effective Thursday, according to an update from the district Wednesday.

In Clayton County, the Kemp Primary School confirmed that students will "operate in a virtual learning environment for the remainder of the week," and the Glascock County Consolidated School in Gibson, Georgia, will continue virtually until at least August 20, it said.

Understaffed hospitals facing rising patient numbers

Increased protection in the community could also be important in reducing the burden on hospitals.

West Virginia Gov. Jim Justice said that for the first time since February 8, there are more than 100 Covid-19 patients in hospital ICUs across the state.

In Oregon, Gov. Kate Brown said ICU beds are about 90% filled, with some hospitals starting their days with fewer than five available ICU beds.

"Oregon hospitals are facing a crisis that threatens to eclipse the most severe bed shortages they've faced at any point in the pandemic," said Pat Allen, Director of the Oregon Health Authority.

In Mississippi, the University of Mississippi Medical Center reported its highest number of Covid-19 patients ever in the pandemic while citing problems with finding nursing staff as the "biggest pain point."

There are some medical, surgical and ICU beds unable to open due to low nursing staff numbers, said Dr. LouAnn Woodward, UMMC Vice Chancellor.

In Texas, Gov. Greg Abbott announced Wednesday that over 2,500 medical personnel will be deployed to hospitals around the state.

"The State of Texas is taking action to ensure that our hospitals are properly staffed and supported in the fight against COVID-19," Abbott said in a statement. "Texans can help bolster the state's efforts to combat the virus by getting vaccinated. The COVID-19 vaccine is safe and effective, and it is our best defense against the virus."

Fauci on hospitalization forecast: It doesn't have to be that way

Ensemble forecasts published Wednesday by the CDC project that new Covid-19 hospitalizations could reach 33,000 by Labor Day, September 6, but we have the power to prevent that, Fauci said.

"You know, predictions really can be modified by what you do in response to them," Fauci said on ABC's "Good Morning America" on Thursday. "And that's the reason why you see myself and many of my colleagues out there talking about why it is so important to get those 93 million people who are eligible to be vaccinated who are not vaccinated. We have a solution to this problem," Fauci said.

"We have the capability and the power to stop that. We just have to act on it, and the first step in that is get vaccinated," he said.

The current seven-day average number of hospital admissions of patients with Covid-19 is 9,712, according to CDC data.

The forecasts predict a total of 630,000 to 662,000 Covid-19 deaths will be reported by September 4. The previous forecast, published August 4, predicted up to 642,000 deaths by August 28.

According to data compiled by Johns Hopkins University, there have been more than 618,000 Covid-19 deaths in the United States.