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.

Tampa Mayor Jane Castor signed an executive order Thursday requiring the use of face coverings at outdoor Super Bowl-related activities to help mitigate the spread of COVID-19 in the Florida city.

The order targets sites where large crowds of people are likely to congregate around the Super Bowl this weekend, with limited ability to remain socially distant from each other. They include "Event Zones" in areas of downtown Tampa and surrounding Raymond James Stadium, as well as "Entertainment Districts," including Ybor City Historic District, the South Howard Commercial Overlay District, the Central Business District and the Channel District.

Those exempt from the order include children under the age of 5, someone communicating with a hearing-impaired individual and people with existing health conditions who would be impaired by a mask.

The Super Bowl will be held on Feb. 7 between the Kansas City Chiefs and hometown Tampa Bay Buccaneers. The mask mandate is in effect now through Feb. 13. Those who violate it could be subject to a $500 fine.

The NFL had previously announced that masks will be required in the stadium unless eating or drinking.

Under a previous order still in effect, masks are required in Tampa at indoor locations outside the home when social distancing cannot be maintained.

ABC News' Will McDuffie contributed to this report