COVID-19 live updates: City sees fourfold increase in pediatric hospitalizations

Nearly 170,000 children tested positive for COVID-19 last week, a roughly 28% jump in two weeks, according to a new report from the American Academy of Pediatrics and the Children’s Hospital Association released on Monday.

The Northeast saw its highest number of pediatric cases of the entire pandemic last week, with nearly 50,000 new cases.

On average, nearly 200 American children are being admitted to hospitals with COVID-19 each day, according to federal data.

Twenty-one million children ages 5 to 17 -- about 40% of that population -- have received at least one vaccine dose.

Severe illness due to COVID-19 remains "uncommon" among children, the American Academy of Pediatrics and the Children’s Hospital Association said. However, the organizations continue to warn that there is an urgent need to collect more data on the long-term consequences of the pandemic on children, "including ways the virus may harm the long-term physical health of infected children, as well as its emotional and mental health effects."

-ABC News' Arielle Mitropoulos

The University of Chicago said students and employees must get a booster shot and have until the end of January to give proof or get an exemption.

The university hopes to fully return to in-person classes on Jan. 3.

Other universities like New York University and Notre Dame are also requiring boosters.

-ABC News' Oren Oppenheim

Queen Elizabeth II has changed her Christmas plans and canceled her traditional family gathering at Sandringham, her Norfolk estate. A royal source told ABC News this was a personal decision and the queen was following a precautionary approach as COVID-19 cases sharply rise in the United Kingdom.

The queen instead will remain at Windsor Castle where her family is expected to visit.

-ABC News' Zoe Magee

WHO DG recommends canceling or delaying holiday events

World Health Organization Director-General Dr. Tedros Adhanom Ghebreyesus on Monday recommended delaying or canceling holiday events.

"There is now consistent evidence that omicron is spreading significantly faster than the delta variant. And it's more likely that people who have been vaccinated or have recovered from COVID-19 could be infected or re-infected," he said.

While everyone wants a return to normal, he said, the fastest way to get there is to make difficult decisions to protect ourselves and others.

"In some cases, that will mean canceling or delaying events," he said. "But an event canceled is better than a life canceled."

-ABC News' Christine Theodorou