COVID-19 updates: Elizabeth Warren tests positive

The National Football League will require that all its vaccinated Tier 1 and 2 employees receive COVID-19 booster shots by Dec. 27, according to a memo sent to all 32 teams within the professional American football league on Monday.

This group of employees includes coaches and other employees who work closely with NFL players and help in essential league operations.

"On November 29, the CDC issued a study showing that the effectiveness of the approved COVID-19 vaccines may decrease over time and has recommended that all eligible vaccinated individuals over the age of 18 should receive a booster shot," the memo states. "Given the increased prevalence of the virus in our communities, our experts have recommended that we implement the CDC’s recommendation."

The memo came as 36 players were added to the NFLS's COVID-19 reserve list. Players are currently not required to receive boosters; but in Monday’s memo, the NFL said teams should consider making boosters available for players and their families.

"Any individual who is not currently subject to the requirement for boosters will be required to obtain the booster within 14 days of becoming eligible," the memo states.

-ABC News’ Katie Conway

The U.S. Air Force gave administrative discharges to 27 personnel who refused to get vaccinated against COVID-19 and comply with the federal government's mandate.

Over 7,000 Air Force members are unvaccinated against COVID-19, which includes about 4,500 who are waiting to see if they are eligible for religious exemption. More than 1,500 religious exemption requests have been denied and those individuals remain unvaccinated.

The Air Force has not granted a single religious exemption, according to officials.

Over 1,000 members have outright refused to get their shots.

More discharges over vaccine refusal are likely, according to an official.

-ABC News' Luis Martinez

California is reinstating an indoor mask mandate from Dec. 15 to Jan. 15.

Half of the state is already under a mask mandate per local rules, according to California Health and Human Services Secretary Mark Ghaly.

California is also tightening restrictions on unvaccinated people at large events. At events with more than 1,000 people, anyone who isn’t vaccinated must show proof of a negative antigen test within 24 hours or a negative PCR test within 48 hours.

State officials also recommend that travelers get tested three to five days before arriving in California.

-ABC News' Matt Fuhrman

Last week, another 164,000 children in the United States tested positive for COVID-19, up by 24% from the week prior, according to a report released Monday by the American Academy of Pediatrics and the Children’s Hospital Association.

COVID-19 cases among U.S. children are "extremely high," the organizations wrote in the report.

Last week the Northeast saw its highest number of pediatric cases since the onset of the pandemic, with nearly 40,000 new cases.

So far, 21 million children ages 5 to 17 nationwide -- about 39.6% -- have received at least one dose of a COVID-19 vaccine.

Severe illness due to COVID-19 remains "uncommon" among children, the organizations wrote in the report. But they continue to warn that there is an urgent need to collect more data on the long-term consequences of the pandemic on kids, including the physical, emotional and mental health impacts.

-ABC News' Arielle Mitropoulos