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

A total of 50 million COVID-19 cases have now been confirmed in the U.S., according to data from Johns Hopkins University.

The U.S. has reported more cases than any other nation in the world. The U.S. currently represents nearly one-fifth of the globe's total 270.5 million cases.

-ABC News' Arielle Mitropoulos

In the weeks following Thanksgiving, the COVID-19 resurgence in the U.S. has escalated rapidly.

The U.S. is averaging more than 118,000 new cases each day -- up by about 41.8% in the last two weeks and up nearly 85% since late October, according to federal data.

Six states with some of the nation's highest vaccination rates are also among the states with the highest new case rates: New Hampshire, Vermont, Massachusetts, Maine, Rhode Island and New York. Experts say cases could be rising in the Northeast partially due to people heading inside in the cold weather.

Daily COVID-19-related hospital admissions increased by 14.4% in the last week and jumped by 48% in the last month, according to federal data.

Pediatric admissions are up by 23.8% in the last week.

-ABC News' Arielle Mitropoulos

Omicron is expected to be the dominant variant in London in the next 48 hours, the Secretary of State for Health and Social Care, Sajid Javid, warned in a statement to Parliament Monday.

Omicron represents 20% of England's cases and 44% of London's cases, Javid said.

"No variant of COVID-19 has spread this fast," Javid said.

Ten people with omicron are in U.K. hospitals.

"Hospitalisations and deaths lag infections by around two weeks," Javid said, "So we can expect those numbers to dramatically increase in the days and weeks that lie ahead."

"In preparation, the UK’s four Chief Medical Officers raised the COVID Alert level to 4, its second-highest level, this was done over the weekend. And NHS England has just announced it will return to its highest level of emergency preparedness: Level 4 National Incident," Javid said. "This means the NHS response to Omicron will be a coordinated as a national effort, rather than led by individual trusts."

Javid also urged people to get booster doses, stating that 40% of adults in the U.K. have gotten boosters so far.

-ABC News' Zoe Magee

Indonesia announced Thursday its first confirmed case of the omicron variant.

The case was detected in a janitor who works at the COVID-19 Emergency Hospital of Kemayoran Athletes Village in Jakarta, according to a statement from Indonesian Health Minister Budi Gunadi Sadikin.

The hospital's cleaning staff are routinely tested and the results for three people were positive for COVID-19 on Dec. 10. Those samples were then sent to a genome sequencing lab, which identified the omicron variant in one of the samples on Wednesday, according to the statement.

Indonesia's Ministry of Health has also identified probable cases of omicron among five travelers who were in quarantine -- two Indonesian citizens who had just returned from the United Kingdom and the United States, and three foreigners from China. Their test samples are being sequenced and the results will be known in a few days, according to the statement.

The health minister urged Indonesians "not to panic and to remain calm," and to get vaccinated against COVID-19 if they haven't already.

"The arrival of new variants from abroad, which we identified in quarantine, shows that our defense system against the arrival of new variants is quite good, we need to strengthen it," Sadikin said. "So it's normal to stay 10 days in quarantine. The goal is not to make it difficult for people who came, but to protect the people of Indonesia."