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 United Kingdom has launched a new advertising campaign that urges pregnant women who have not yet received a COVID-19 vaccine or booster shot to do so as soon as possible.

Testimonies of pregnant women who have had the shots will be played out in ads across U.K. radio stations and on social media starting Monday. The new campaign urges pregnant women "don't wait to take the vaccine" and highlights the risks of COVID-19 to both mother and baby as well as the benefits of getting vaccinated, according to a press release from the U.K. Department of Health and Social Care.

The press release cited the latest data from the U.K. Health Security Agency that suggests COVID-19 vaccination is safe for pregnant women and provides strong protection against the virus for both mother and baby. The press release also cited data from the U.K. Obstetric Surveillance System that shows more than 96% of pregnant women hospitalized with COVID-19 symptoms between May and October 2021 were unvaccinated, and a third of them required respiratory support. Around one in five women who are hospitalized with COVID-19 need to be delivered preterm to help them recover, and one in five of their babies need care in the neonatal unit.

"Getting a COVID-19 vaccine is one of the most important things a pregnant woman can do this year to keep herself and her baby as safe from this virus as possible," Lucy Chappell, chief scientific adviser to the U.K. Department of Health and Social Care, said in a statement Monday. "We have extensive evidence now to show that the vaccines are safe and that the risks posed by COVID-19 are far greater."