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

Some 20 million people across three Chinese cities are now under lockdown due to COVID-19 outbreaks.

Anyang, home to 5.5 million people, was the latest city to lock down its residents after discovering two cases of the fast-spreading omicron variant. Another 13 million people are under lock down in Xi'ian and 1.1 million in Yuzhou, with both cities still battling the highly contagious delta variant. Neither has reported any cases of omicron.

Meanwhile, restrictions have been imposed in the port city of Tianjin, about 80 miles southeast of Beijing, which is to host the 2022 Winter Olympics next month. The city's 14 million people are being tested for COVID-19 after two locally transmitted cases of omicron were detected over the weekend -- the first for mainland China.

-ABC News' Karson Yiu