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.

Iowa will roll back several COVID-19 restrictions starting Sunday, including a requirement that masks be worn indoors.

Gov. Kim Reynolds issued a new proclamation Friday that does not include any requirements around facial coverings.

Under a previous proclamation, set to expire Saturday, masks were required in indoor public spaces when social distancing for at least 15 minutes was not possible.

The new proclamation also does not impose any restrictions on public gatherings, which previously had to follow social distancing and other guidelines.

Regarding gatherings, the new proclamation states, "I strongly encourage that all businesses or other employers remaining open with in-person operations take reasonable measures under the circumstances of each establishment to ensure the health of employees, patrons and members of the public, including social distancing practices, increased hygiene practices and other public health measures to reduce the risk of transmission of COVID-19 consistent with guidance issued by the Iowa Department of Public Health."

The governor has been loosening restrictions in recent weeks around public gatherings for sports, restaurants and bars as new COVID-19 cases and hospitalizations have trended downward from peaks in November.

Iowa, which initially issued its mask requirement in mid-November, will be one of 15 states that doesn't have a statewide mask mandate, according to a tally by Masks4All.