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

The United Kingdom reported 93,045 new cases in the last 24 hours, breaking a daily record for the third day in a row.

The total number of cases over the last week now stands at 477,229, a 38.6% increase from the previous week.

-ABC News' Guy Davies

Friday's four Radio City Rockettes shows have been canceled due to breakthrough COVID-19 cases in the New York City production.

Plans for future shows haven't been determined.

-ABC News' Aaron Katersky

The Centers for Disease Control and Prevention on Friday endorsed a practice in schools called “test-to-stay,” which allows unvaccinated kids and staff to test instead of quarantine after being exposed to COVID-19.

The CDC says the practice can be employed in addition to other mitigation measures, such as vaccination and at least 3-feet of physical distance among students wearing masks.

The new guidance follows two studies out of Los Angeles County, California, and Lake County, Illinois. Both studies found no significant transmission in school when test-to-stay was used.

The studies were conducted before the omicron variant was detected in the U.S.

-ABC News' Anne Flaherty

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