Assistant Secretary of Defense for Public Affairs John Kirby tweeted that the Pentagon is "pausing" the plan to move forward with vaccinations for detainees at Guantanamo Bay.

"We’re pausing the plan to move forward, as we review force protection protocols," Kirby said. "We remain committed to our obligations to keep our troops safe."

No detainees have been vaccinated yet, he said.

ABC News’ Molly Nagle contributed to this report.

Hard-hit California has surpassed 40,000 deaths from COVID-19, according to the state’s Department of Public Health.

At least 40,216 people in the Golden State have lost their lives, which equals about 1 in every 1,000 Californians.

ABC News’ Matt Fuhrman contributed to this report.

Nashville's Music City Center opened Saturday as a mass vaccination site.

Those 75 and older who already have an appointment booked can get vaccinated at the concert venue, according to ABC Nashville affiliate WKRN.

"We think that we’ll be able to do up to 1,000 first doses here and up to 1,000 second doses here a day, once we receive enough vaccine for that,” Metro Nashville Health Department Interim Medical Director Gill Wright told WKRN.

One case of the South African B.1.351 variant has been confirmed in the Baltimore metro region, Maryland Gov. Larry Hogan said.

"The individual has not traveled internationally, making community transmission likely," Hogan’s office said. "Comprehensive contact tracing efforts are underway to ensure that potential contacts are quickly identified, quarantined, and tested.

"The B.1.351 variant has not been shown to cause more severe illness or increased risk of death when compared to other variants. The variant is believed to be more transmissible than other strains," Hogan’s office said. "Additional research is still required to determine the effectiveness of available vaccines against the B.1.351 variant. However, initial evidence suggests that vaccines are still likely to be protective against the variant."

The United States’ first cases of the South African variant were confirmed this week in two people in South Carolina.

The California Department of Public Health lifted a stay-at-home order for all regions statewide on Monday.

Four-week intensive care unit capacity projections for the three regions that had still been under the order -- San Joaquin Valley, Bay Area and Southern California -- are now above 15%, the threshold that allows regions to exit the order. The Sacramento region exited the order on Jan. 12 and the Northern California region never entered the order, according to a press release from the California Department of Public Health.

The move allows all counties statewide to return to the rules and framework of California's "Blueprint for a Safer Economy" and color-coded tiers that indicate which activities and businesses are open based on local COVID-19 infection rates and test positivity. The majority of the counties are in the strictest -- or purple -- tier. Individual counties may choose to impose stricter rules, according to the press release.

"Californians heard the urgent message to stay home as much as possible and accepted that challenge to slow the surge and save lives," Dr. Tomas Aragon, director of the California Department of Public Health, said in a statement. "Together, we changed our activities knowing our short-term sacrifices would lead to longer-term gains. COVID-19 is still here and still deadly, so our work is not over, but it’s important to recognize our collective actions saved lives and we are turning a critical corner."

California, home to nearly 40 million people, has the highest tally of diagnosed COVID-19 cases of any U.S. state, with more than 3.1 million, according to a real-time count kept by Johns Hopkins University.