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.
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
Massachusetts officials have purchased 2.1 million at-home COVID-19 tests to give for free to 102 towns with the highest percentage of people below the poverty level, Gov. Charlie Baker said.
The tests come in packs of two and can be completed at home in 15 minutes.
"Each city or town will be able to determine how best to distribute tests within their community," Baker's office said in a statement Monday.
