Pharmacies in Washington have finished administering the first round of COVID-19 vaccines for residents of the state’s nursing homes, marking a major milestone in protecting those among the most vulnerable from the deadly virus.

The initial doses, provided largely through a federal partnership with CVS and Walgreens, were completed Thursday, the Washington State Department of Health (DOH) said. Both pharmacies had previously said they expected to finish the first vaccinations by Jan. 25. Some nursing homes received vaccines through other, smaller providers.

“Shout-out to the many pharmacies helping us protect the most vulnerable Washingtonians,” DOH said Thursday evening in a tweet.

The two pharmacy giants began administering vaccines in nursing homes on Dec. 28 and a week later in other long-term care sites, including assisted living facilities and adult family homes. The effort to vaccinate those residents is taking longer than expected, with some facilities reporting delayed clinic dates or an inability to schedule visits.

Long-term care facilities account for about 5% of total cases but more than half the state’s COVID-19 4,065 deaths. Nursing homes have fared the worst, as 95% of the facilities have reported at least one outbreak since the start of the pandemic, according to the state Department of Social and Health Services.

The virus continues to be widespread in senior facilities, though the number of sites with at least one active COVID-19 case has leveled off since a Jan. 12 peak, when 596 of 4,164 facilities reported at least one infection.