COVID-19 updates: Elizabeth Warren tests positive

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

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