States that instituted mask mandates reported a decline in COVID-19 hospitalizations, according to a new report from the Centers for Disease Control and Prevention.

Researchers analyzed hospitalization data in 10 states with mask mandates between March and October of last year. They found a 5.5% decline in weekly COVID-19 hospitalizations among adults, compared to the period before the mandates were implemented.

In addition to reducing virus exposure and transmission, masks are part of a multi-pronged strategy to "reduce strain on the health care system," the researchers note, adding that masks likely have a direct effect on COVID-19 illness and death.

The researchers did not examine whether other policies, such as school closings and physical distancing recommendations, contributed to the decline. The results were published Friday in the CDC's Morbidity and Mortality Weekly Report.

-ABC News' Eric Strauss contributed to this report.

Former Yankees pitcher Mariano Rivera will join Mayor Bill de Blasio at Yankee stadium Friday afternoon to celebrate the opening of a mass vaccination site at the stadium.

The site, which will be reserved for residents from the Bronx, will be open daily from 8 a.m. to 8 p.m. and is meant to ensure that Black and Latino residents have equal access to the vaccine. It will be open 24 hours a day when more vaccine supply is available, according to the mayor.

"I think it’s going to be extraordinary," de Blasio told WNYC on Friday. "We are going to have a wonderful celebration of this place opening up. I will be joined by Mariano Rivera, who will help us get this message out. This is for people of the Bronx, people who haven’t been able to get vaccinated."

Bronx residents who want to book an appointment should go to  or call 1-833-SomosNY.

-ABC News' Aaron Katersky contributed to this report.

So far, 8% of the U.S. population has received one or more doses of COVID-19 vaccines, according to official figures released Friday by the U.S. Department of Health and Human Services.

In total, 35,203,710 vaccine doses have been administered nationwide. About 27.9 million people -- 8% of the population -- have received one or more doses, while 6.9 million people -- 2% of the population -- have received two doses.

ABC News' Josh Margolin contributed to this report.

U.S. President Joe Biden's administration announced Friday that 1,110 active-duty military personnel will be deployed across the country to assist with COVID-19 vaccinations.

The announcement was made during a press briefing at the White House in Washington, D.C.

The troops, sourced from across the U.S. Army, Air Force, Navy and Marine Corps, will be split up into five teams of 222 personnel that will be assigned to support five COVID-19 vaccination centers run by the U.S. Federal Emergency Management Agency (FEMA), according to a fact sheet on the initiative released by the Office of the Secretary of Defense.

FEMA and the U.S. Department of Defense will jointly determine when the troops are no longer needed for vaccination support, according the fact sheet.

ABC News' Matt Seyler contributed to this report.

Dr. Stephen Hoge, president of American biotechnolgy company Moderna, said he's hopeful that vaccines can help the U.S. population achieve herd immunity against the novel coronavirus by mid-year.

"It really depends what you think herd immunity needs to be. But if you assume 50 to 70% of the population, then we're working hard ourselves and the other manufacturers to make sure that's a possibility really in the late spring, early summer," Hoge told ABC News chief anchor George Stephanopoulos in an interview Monday on "Good Morning America."

"It's ultimately going to depend upon the delivery of those vaccines, and so that's something that the states and the health care providers in this country are ultimately leading the way on as well as Americans deciding they want to receive that vaccine," he added. But we're optimistic that by the middle of the year, we'll be able to achieve those sorts of numbers."

Moderna is ramping up production of its COVID-19 vaccine and is working to clear any "bottlenecks" in the supply chain, according to Hoge.

"At this point, a lot of the logistical bottlenecks that we're running into are problems we can solve on our own," he noted. "We're in good shape."

Hoge, who was a resident physician in New York City, said data currently shows that existing vaccines are still effective against all emerging strains of the virus. But the variant first identified in South Africa "is of some concern because it looks like it could hide from the vaccine a little better than others," he said.

"So our approach in Moderna is going to be to develop a booster vaccine so that if the South African variant or any other variant becomes a concern, we'll be able to offer a way to identify that, prevent it from hiding from the vaccine," he said.