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.
Sen. Cory Booker D-NJ revealed on Twitter that he has tested positive with a breakthrough case of COVID-19.
Booker said he received both vaccine doses and his booster shot and his symptoms are "relatively mild."
He added that he's "certain" that if he had not received the shots, he "would be doing much worse."
I learned today that I tested positive for COVID-19 after first feeling symptoms on Saturday. My symptoms are relatively mild. I’m beyond grateful to have received two doses of vaccine and, more recently, a booster – I’m certain that without them I would be doing much worse.
— Sen. Cory Booker (@SenBooker) December 20, 2021
Booker's announcement came hours after Sen. Elizabeth Warren D-Mass., revealed her breakthrough case. Warren also said her symptoms are mild.
In a tweet Sunday night, Sen. Elizabeth Warren, D-Mass., announced that she "tested positive with a breakthrough case" on Sunday. Warren said she's experiencing "mild symptoms."
The progressive senator also indicated that she is fully vaccinated and has received her booster shot.
I regularly test for COVID & while I tested negative earlier this week, today I tested positive with a breakthrough case. Thankfully, I am only experiencing mild symptoms & am grateful for the protection provided against serious illness that comes from being vaccinated & boosted.
— Elizabeth Warren (@SenWarren) December 19, 2021
New York state recorded over 20,000 positive COVID-19 cases for the third day in a row, Gov. Kathy Hochul's office said.
Sunday's total of 22,478 positive cases is the new single-day record, according to the data.
Over 542 patients were admitted to hospitals across the state for COVID-19 symptoms over the last 24 hours, the governor's office said.
There are 3,880 currently hospitalized in the state with the virus, the data showed.
Hochul reiterated her message to New Yorkers to get their vaccinations and boosters and follow health guidelines as the omicron variant continues to spread.
"This is not March of 2020, we are not defenseless," she said in a statement. "We have the tools to protect ourselves and the vulnerable loves ones in our families: Get vaccinated, get the booster and wear a mask when indoors or in large gatherings."
As of Sunday, 70.9% of all New York state residents have completed their vaccinations, the state data showed.
New York City Mayor Bill de Blasio warned that the city will have to brace for a jump in COVID-19 cases as the omicron variant continues to spread.
"We expect omicron to be a fast and temporary phenomenon. We expect these next weeks to see a very, very big surge in the number of cases, more than we've seen previously," he said during a news conference Sunday.
Roughly 162 patients were confirmed positive in the hospital, the mayor said. Hospitalizations have gone up, but not at the rate health officials were expecting.
"It will undoubtly grow a bit," de Blasio said.
The city recorded 5,731 new cases of COVID-19 Sunday.
The mayor urged New Yorkers to get vaccinated and to get their booster shots. The city's health department said as of Sunday 71% of all residents are fully vaccinated.
De Blasio also recommended that people wear masks indoors.
The city will focus on vaccination efforts for children and to increase booster access in nursing homes, he said.
At-home testing kits will be handed out at high volume testing sites, according to the mayor.
With winter closing in and COVID-19 cases on the rise, hospitals across the United States are once again facing the pressures of caring for thousands of patients.
More than 67,000 people are currently hospitalized with COVID-19 nationwide, according to federal data.
Rebecca Long, lead nurse in a COVID-19 intensive care unit at Nebraska Medical Center in Omaha, told ABC News that she and her team "literally do not have any ICU beds" available.
"I don't want anyone else's family member or loved one to have to be in the position where we say, like, we can't help you because we don't have the resources," Long said. "As health care providers, all we want to do is help people and we can't because we physically can't."
Dr. Kyle McCarty, medical director of emergency services at both HSHS St. Mary's and HSHS St. Vincent hospitals in Green Bay, Wisconsin, told ABC News that health care workers are feeling burned out after "being asked to do more with less."
"We're exhausted by the knowledge that we are the duct tape that is preventing a complete collapse of the health care system," McCarty said. "There's a national shortage of hospital staff, which is making it difficult to take care of patients the way that we want it. There aren't enough inpatient beds for the patients that need to be admitted to the hospital."
"This is a call for reinforcements, not a warning to stay away, because we don't want this to be the new normal," he added. "If we can recruit more health care teammates, it doesn't have to be."
-ABC News' Arielle Mitropoulos
