PORTLAND, Maine (AP) Maine expanded eligibility for the coronavirus vaccine to everyone age 50 and older on Tuesday.

The state is using age-based tiers to apportion the limited number of coronavirus vaccines it has access to. Everyone age 16 and older will be eligible on April 19.

The office of Gov. Janet Mills, a Democrat, said more than 580,000 doses of coronavirus vaccines have been administered in Maine. More than a quarter of the state’s population has received at least a first dose.

Only Maine residents are eligible to receive a vaccine in Maine at the moment, state health authorities said.