Pharmacies in the United States will begin to offer COVID-19 vaccines at  from February 11, part of efforts to rapidly increase the rate of vaccinations in the country.

The White House’s COVID-19 response coordinator Jeff Zients told reporters on Tuesday that because of supply constraints, the program would initially be limited to 6,500 participating pharmacies nationwide, before eventually expanding to 40,000.

“This will provide more sites for people to get vaccinated in their communities. And it’s an important component to delivering vaccines equitably,” he said.

Major chains like Walgreens, CVS Pharmacy, Walmart and Rite Aid are among those participating and the program is planned to work on an appointment basis, as people become eligible on the basis of their priority group.

The administration will allocate a million doses to the pharmacies in the first week, in addition to 10.5 million doses it is allocating to states and other territories starting this week.

The state allocations are up 22% since January 20, when the administration of President Joe Biden took office, according to a statement.

More than 32.2 million shots have so far been administered, with just under six million people receiving both doses of the Pfizer or Moderna vaccines, according to the latest official data.

After initial setbacks, states are ramping up their vaccine administration rate while the federal government is working with vaccine makers to try to increase supply.

The Biden administration is targeting 150 million shots injected within its first 100 days of office that end on April 20.

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It’s widely expected that authorities will soon clear a third vaccine for emergency use, after Johnson & Johnson last week announced results from a multi-continent trial that showed its shot was effective, especially against severe COVID-19.

Though less protective than Pfizer and Moderna’s, J&J’s vaccine has the advantages of being one-shot, and storable at fridge temperatures rather than in deep freezers.

Also on Tuesday, the Biden administration announced it would reimburse states for their COVID-related emergency funds and national guard deployments going back to January 2020, a move that would free up $3-$5 billion the states could then use on vaccine rollout efforts.