Nearly 30% of all Covid-19 cases last week occurred in children, according to data from the American Academy of Pediatrics (AAP) and the Children's Hospital Association (CHA)—news that comes as former FDA Commissioner and Pfizer board member Scott Gottlieb said Covid-19 vaccines for children could be authorized by the end of October.

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Children representing a growing portion of Covid-19 cases

According to AAP and CHA's data, for the week ending in Sept. 9, children represented 28.9% of all Covid-19 cases, an increase from 26.8% in the previous week.

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In total, AAP and CHA found that pediatric Covid-19 cases have represented 15.5% of all Covid-19 cases since the start of the pandemic.

According to AAP, these cases have been increasing significantly in recent months. In early July, children accounted for 71,726 cases. For the week ending in Sept. 9, that number was 243,373, a nearly 240% increase.

"After declining in early summer, child cases have increased exponentially with nearly 500,000 cases in the past two weeks," AAP said in a statement.

Children's National Hospital in Washington, D.C. last weekend reached capacity, with all 323 beds in the hospital's acute care wing filled, according to CMO David Wessel. Of those patients, 22 have Covid-19.

The main cause of Children's National reaching capacity has been RSV, a respiratory virus that infects the lungs and breathing passages, Wessel said.

Although more children have been developing Covid-19, the disease remains mild in the majority of pediatric cases. According to the Washington Post, children have a more robust innate immune response than older adults do, which enables most children to quickly fight off the coronavirus before it spreads throughout the body.

AAP and CHA's data shows that, in the 24 states reporting age-specific hospitalization data, children accounted for just 1.6% to 4% of all hospitalizations. And among the 45 states reporting Covid-19 mortality by age, children accounted for just 0.27% or less of Covid-19 deaths.

When will a Covid-19 vaccine be ready for children?

According to former FDA Commissioner Scott Gottlieb, who is also a board member at Pfizer, children could be able to get vaccinated by Halloween.

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Gottlieb said on Sunday that Pfizer expects to finish preparing data on vaccines for children ages five to 11 for FDA by the end of this month.

"The FDA says it will be a matter of weeks, not months, to make a determination if they're going to authorize vaccines for kids between five to 11," Gottlieb said. "I interpret that to be perhaps four weeks, maybe six weeks."

Pfizer CEO Albert Bourla on Tuesday said Pfizer intends to release data on its Covid-19 vaccine in children ages six months to five years old as early as the end of October. Bourla also confirmed that vaccine data on children ages five to 11 could be ready by the end of this month.

"Then, it is up to the FDA to take their time, and then make a decision," Bourla said.

Peter Marks, FDA's top vaccine regulator, said last month that FDA would move as "swiftly" as it can to approve vaccines for children under the age of 12 once data is submitted.

"Currently, there are still trials ongoing and so the agency has to wait for the company to submit the data for those trials," he said. "We certainly want to make sure that we get it right."

Meanwhile, CDC Director Rochelle Walensky on Monday said the agency is working quickly on a Covid-19 vaccine for younger children, which she hopes will be ready by the end of the year. (Bean, Becker's Hospital Review, 9/14; Cook, NBC Washington, 9/14; Christensen/Vera, CNN, 9/13; Gale, Bloomberg/Washington Post, 9/15; Lovelace, CNBC, 9/14)