Coronavirus updates: State reports over 49,000 new cases, 468 new deaths

Sandra Lindsay, director of critical care nursing at Long Island Jewish Medical Center in New York City, became the first person in the United States to complete a two-dose COVID-19 vaccine course outside of a clinical trial on Monday, 21 days after she was given her initial Pfizer/BioNTech vaccination on Dec. 14.

"I feel good," Lindsay told reporters Monday. "I don't feel any way different before I got it. I hope the vaccine is available to everyone as it was for me," she added.

The Pfizer vaccine has been shown to be 95% effective after two doses.

The United Kingdom is expected to announce tight lockdown restrictions Monday, following a recommendation from the nation's chief medical officers to move to the highest COVID-19 alert level -- alert level 5 -- across the country. The U.K. has been at alert level 4 since September.

"Cases are rising almost everywhere, in much of the country driven by the new more transmissible variant," the chief medical officers said in a statement Monday. "We are not confident that the NHS can handle a further sustained rise in cases and without further action there is a material risk of the NHS in several areas being overwhelmed over the next 21 days."

British Prime Minister Boris Johnson is set to announce additional measure to control the virus during a televised address Monday evening.

-ABC News' Zoe Magee contributed to this report.

The entire 2021 NCAA men's championship basketball tournament will be held in Indiana, the NCAA announced Monday.

The NCAA is partnering with the local health department in Marion County to test players, coaching staff, administrators and officials for COVID-19. Teams will stay on dedicated hotel floors and meetings and dining halls with be socially distanced.

"The Marion County Health Department has approved medical protocols shared by the NCAA and will continue collaborating with the NCAA leading up to and during the championship," the NCAA said in a statement.

The majority of those contests will be held in Indianapolis.

The 2020 NCAA Tournament was canceled due to the COVID-19 pandemic.

ABC News' Joshua Hoyos and Matthew Stone contributed to this report.

A record-breaking 125,544 people in the United States are currently hospitalized with COVID-19, with six states -- Alabama, California, Georgia, North Carolina, South Carolina and Texas -- reporting record hospitalizations on Jan. 3.

While daily COVID-19 figures remain skewed because of a holiday-related backlog, data from December shows a grim trend, according to an ABC News analysis of data collected by The COVID Tracking Project, a volunteer-run effort to track the U.S. outbreak. December was the worst month so far for infections, hospitalizations and deaths. In less than eight weeks, the U.S. jumped from 10 million cases to 20 million cases on Jan. 1.

Over the course of December, the U.S. reported 77,082 deaths from the virus, bringing the national death toll to 351,590, according to data from Johns Hopkins University. The U.S., which leads the world in COVID-19 fatalities, accounts for nearly 20% of the world's total death toll.

In different terms, 1 in every 940 Americans has died of COVID-19.

ABC News' Arielle Mitropoulos contributed to this report.