COVID-19 updates: Elizabeth Warren tests positive
The senator says she's experiencing "mild symptoms."
As the COVID-19 pandemic has swept the globe, more than 5.3 million people have died from the disease worldwide, including over 806,000 Americans, according to real-time data compiled by Johns Hopkins University's Center for Systems Science and Engineering.
About 61.4% of the population in the United States is fully vaccinated against COVID-19, according to data from the Centers for Disease Control and Prevention.
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Harvard joins list of universities mandating boosters
Harvard University will require boosters for all eligible members of the community, school officials said Thursday.
Earlier this week, Harvard warned of an increase in cases, saying the rise can be attributed to social events following the Thanksgiving break.
Omicron is likely already on campus, university officials added.
Harvard joins a growing list of colleges and universities moving to require third doses next semester for those eligible. Other schools include Stanford, NYU, University of Notre Dame, Syracuse, Smith College and Wellesley College.
-ABC News' Arielle Mitropoulos
Illinois reports highest case number of the year
In Illinois, 11,858 new cases were reported on Thursday -- the highest daily case number of all of 2021, ABC Chicago station WLS reported, citing state health officials.
Illinois confirmed its second omicron case Wednesday, detected in a suburban Chicago resident. That person is asymptomatic and vaccinated, WLS reported.
CDC recommends opting for Pfizer or Moderna over J&J when there's a choice
The Centers for Disease Control and Prevention has signed off on its advisory committee's recommendation that people who have a choice should get an mRNA vaccine, either Pfizer or Moderna, over the single-shot Johnson & Johnson vaccine.
The updated recommendation comes after a review of new CDC data on rare blood clots linked to the J&J vaccine.
"Today's updated recommendation emphasizes CDC's commitment to provide real-time scientific information to the American public," CDC Director Dr. Rochelle Walensky said in a statement. "I continue to encourage all Americans to get vaccinated and boosted."
Omicron now makes up nearly 100% of strains found in Orlando wastewater samples
The new omicron variant makes up nearly 100% of the strains found in wastewater samples in Orlando, Florida, officials said Thursday.
"It escalated rapidly," Orange County Utilities spokeswoman Sarah Lux told ABC News.
In its first test for the variant last Thursday, the department found no evidence of omicron in the community's wastewater, she said. On Saturday, it represented about 30% of the strains found in the samples, and by Tuesday, nearly 100%.
"So, we're talking about zero to nearly 100 in a matter of a week," Lux said.
All parts of the county are seeing an increasing presence of the omicron variant, she said. The southern area, home to the theme parks, has seen the highest amount of virus remnants, followed by the eastern area, which is home to the University of Central Florida.
-ABC News' Arielle Mitropoulos
UK sees highest number of cases since start of pandemic
The United Kingdom confirmed 78,610 COVID-19 cases in the last 24 hours -- the highest daily number since the start of the pandemic, officials said Wednesday.
Prime Minister Boris Johnson encouraged everyone to continue to get vaccinated and boosted. He said 650,000 boosters were administered Tuesday and now 45% of all adults have received a booster.
-ABC News' Joe Simonetti