Maryland Gov. Larry Hogan announced that the state will enter Phase 1b of its coronavirus vaccine rollout on Monday, meaning residents age 75 and older can now receive the vaccine.

As of Thursday, 547,000 doses had been distributed to vaccination sites statewide, making up over 99% of Maryland’s supply, Hogan said. Approximately 202,254 of those doses have been administered.

Starting next week, hospitals and local health departments are expected to open up vaccine clinics for seniors, beginning Phase 1b with the remaining supply of doses. This phase also includes staff and residents of assisted living and group homes, as well as K-12 teachers and childcare workers.

Phase 1c, which begins Jan. 25, includes Marylanders age 65 to 74; healthcare workers and first responders not covered in Phase 1a; and other essential workers in lab services, food production and grocery stores, manufacturing, public transit, and the Postal Service.

“As was expected, we are now entering the most challenging phase of the pandemic,” Hogan said at a press conference. “And the solution to bringing this crisis to an end will be vigilance and vaccines.”

We are activating Phase 1B to begin statewide on January 18, which includes Maryland age 75 and older; assisted living and other congregate facilities; and K-12 teachers, support staff, and childcare providers. pic.twitter.com/X405769Xne

— Governor Larry Hogan (@GovLarryHogan) January 15, 2021

A more contagious strand of the coronavirus was found Tuesday in two Maryland residents, confirming fears that the strand — first detected in the United Kingdom — could appear in the region. Hogan said at Thursday’s press briefing that while the discovery of the variant has worried public health officials, the “good news is it has not been shown to cause more severe illness or increased risk of death.”

Hogan said the state’s main goal is “to get more shots into arms, the arms of more people in our vulnerable populations as quickly as they can.”

The governor warned that the distribution will “take a long time,” as 1.5 million people are included in Phase 1 of the plan (each person needs two doses to be fully vaccinated). About 12 million doses are needed to vaccinate all Maryland residents, and the state has received just 4.5% of that supply so far, Hogan said.

The Maryland National Guard is involved in the vaccine distribution, so far, providing Prince George’s and Charle’s County with additional staffing. Hogan also announced a state health order that allows out-of-state volunteers to administer doses.

Maryland residents who are eligible for the vaccine can visit the state’s website to find a nearby clinic.