The U.S. Department of Defense announced a $442.1-million contract with Pfizer to produce 835,000 doses of Paxlovid, the first oral antiviral authorized to treat Covid-19.

Pfizer CEO Albert Bourla said on Monday he expected distribution of the pill to rise "exponentially" in the coming months, with 6 million courses available by March.

The Pentagon's announcement came less than a week after the White House announced it would double its purchase of Paxlovid from 10 million to 20 million treatment courses, with 10 million treatment courses ready by June.

The estimated completion for the Pentagon's contract was set for the end of March, officials said on Monday.

ABC News' Sasha Pezenik

The Chicago Teachers Union House of Delegates voted Monday to end the work stoppage, Chicago Mayor Lori Lightfoot said in a press conference.

Lightfoot said teachers will be back on Tuesday, and students will return on Wednesday.

"To the parents, we heard you. We will never, never, not have you at the table with us in the future. No one wins when our students aren't where they can learn their best," she said.

She explained that city officials and the CTU reached an agreement on when a school will go remote.

"Teachers are so important to who our young people become. That's not what this was about. We love our teachers and continue to support our teachers," Lightfoot added. "I will always be on the side of our children and their families."

The news of the work stoppage comes after Chicago Public Schools, the nation’s third-largest district, canceled classes for a fourth day Monday amid negotiations with the teachers’ union over remote learning and COVID-19 safety protocols.

"The Chicago Teachers Union House of Delegates has voted tonight to suspend the Union's remote work action while rank-and-file membership votes on the proposed agreement," CTU tweeted Monday night.

Amidst the nation's most significant COVID-19 infection surge yet, new data released on Monday shows that more than half a million children tested positive for COVID-19, last week, according to a weekly report from the American Academy of Pediatrics and the Children’s Hospital Association.

Last week alone, 580,000 children tested positive for COVID-19, marking a nearly three times more than two weeks prior, according to the organizations.

A total of 8.47 million children have tested positive for the virus since the onset of the pandemic, and nearly 11% of these children have tested positive in the past two weeks alone.

Children accounted for about 17.3% of the reported weekly COVID-19 cases last week, down again from previous weeks, when children accounted for more than a quarter of all new cases. For context, children under 18 make up 22.2% of the U.S. population.

Still, recent COVID-19 data could be skewed due to erratic and volatile reporting following the holidays. An artificial increase in the numbers could have resulted as more Americans get tested.

-ABC News' Arielle Mitropoulos

In Harris County, Texas, which encompasses Houston, Harris County Judge Lina Hidalgo has raised the COVID-19 threat level to “red” -- the highest level -- due to an uptick in hospitalizations.

COVID-19 patients occupy 18% of all ICU beds in the county.

-ABC News' Matt Fuhrman

The American Red Cross said Tuesday that it is facing its worst blood shortage in over a decade.

"While some types of medical care can wait, others can't," Dr. Pampee Young, chief medical officer of the American Red Cross, said in a statement. "Hospitals are still seeing accident victims, cancer patients, those with blood disorders like sickle cell disease, and individuals who are seriously ill who all need blood transfusions to live even as Omicron cases surge across the country."

The American Red Cross, which supplies about 40% of the nation's blood, said it saw donor numbers fall as the delta variant of COVID-19 spread in August. The number of blood donors has fallen by about 10% since the beginning of the pandemic. That trend continued as omicron spread, according to the organization.

"We’re doing everything we can to increase blood donations to ensure every patient can receive medical treatments without delay, but we cannot do it without more donors," Young said. "We need the help of the American people."