More than 4,700 COVID-19 patients are in Ohio hospitals, the highest number of all of 2021 -- and hospitalization numbers are quickly approaching an all-time high, Gov. Mike DeWine's office said.

DeWine said he's calling up 1,050 National Guard members to help overwhelmed hospitals beginning on Monday.

The potential timeline for when children under 5 may have an authorized vaccine is now being pushed back.

Data for a two-shot vaccine was initially expected by the end of the year, but now Pfizer/BioNTech say they hope to have data with a third shot in the first half of 2022.

Pfizer/BioNTech said they "will amend the clinical study evaluating the safety, tolerability, and immunogenicity of the Pfizer-BioNTech COVID-19 Vaccine in children 6 months to under 5 years of age. The study will now include evaluating a third dose of 3 µg at least two months after the second dose of the two-dose series to provide high levels of protection in this young age group."

An early look into the study data suggested that the two doses at a smaller volume was not as effective for kids ages 2 to 5 as it was for the 16 to 25 population, so scientists are going to add a third dose and see if the vaccine is as effective. There were no safety issues reported in the early data analysis.

Pfizer/BioNTech added in a statement, “The decision to evaluate a third dose of 3 µg for children 6 months to under 5 years of age reflects the companies’ commitment to carefully select the right dose to maximize the risk-benefit profile. If the three-dose study is successful, Pfizer and BioNTech expect to submit data to regulators to support an Emergency Use Authorization (EUA) for children 6 months to under 5 years of age in the first half of 2022.”

-ABC News' Eric M. Strauss

Americans in their 30s are accounting for the highest case rate of any age group, according to federal data.

The U.S. is now reporting nearly 120,000 new cases each day. The daily case average has surged by nearly 86.3% since late October, according to federal data.

Thirty-three states, as well as Washington, D.C., and New York City, have seen at least a 10% jump in daily cases over the last two weeks.

New Hampshire currently holds the nation's highest case rate, followed by Rhode Island, Maine, Wisconsin, Connecticut and Massachusetts, according to federal data.

-ABC News' Arielle Mitropoulos

White House COVID-19 response coordinator Jeff Zients warned Friday that the unvaccinated are "looking at a winter of severe illness and death -- for yourselves, your families and the hospitals you may soon overwhelm."

CDC director Rochelle Walensky said she expects omicron to become the dominant variant in the coming weeks.

Asked whether the CDC will change its guidance on vaccinated people quarantining after exposure, which they currently don't have to, Walensky said, "We are actively following the science in that area, with regard to how the viral burden is both among vaccinated people and unvaccinated people, and the natural history of that viral burden with regard to isolation."

"And as that science emerges, we will update our evidence if need be," she said.

-ABC News' Cheyenne Haslett

School leaders at both New York University and Princeton University announced Wednesday that they will take steps to cancel end-of-year events and move winter exams online amid a surge in COVID-19 cases on their respective campuses.

"Given that we've seen an uptick in cases among undergraduates during the last 24 hours -- including suspected cases of the highly contagious Omicron variant -- we hope to avoid letting the final exam schedule interfere with students’ travel home for Winter Break," Princeton University's dean, Jill Dolan, and vice president for campus life, Rochelle Calhoun, said in a joint statement. "We certainly don’t want you remaining on campus in required isolation through the holidays."

All indoor gatherings with food and those where face coverings cannot be worn must be canceled or postponed at Princeton's New Jersey campus from Thursday through Jan. 7, according to the statement.

A statement from New York University's provost, Katherine Fleming, executive Vice President, Martin Dorph, and head of the COVID-19 prevention and response team, Dr. Carlo Ciotoli, said they "strongly encourage that final examinations and/or assessments be changed to remote/online format." All discretionary, non-essential, non-academic gatherings and events at the school's campus in New York City must be canceled "immediately," according to the statement.

"The continuous review of the data from our COVID-19 testing program has indicated a considerable acceleration in the rate of new cases in our community," they said. "It’s not a cause for alarm, but it is a cause for concern, caution, and appropriate actions."

NYU has also joined a growing list of colleges and universities across the nation that are requiring all eligible members of the school community, including faculty and students, to be fully vaccinated against COVID-19 and receive a booster shot ahead of the upcoming spring semester.

Meanwhile, officials at Cornell University in Ithaca, New York, announced Tuesday that they have moved the campus into a "level red" alert after identifying evidence of suspected cases of the omicron variant in a "significant" number of the school's COVID-19 positive samples from students.

According to data from the Centers for Disease Control and Prevention, the omicron variant is estimated to account for more than 13% of newly confirmed COVID-19 cases in the New York and New Jersey area -- the highest proportion of any region of the United States.

-ABC News' Chris Donato and Arielle Mitropoulos