In this April 12, 2021, file photo, the mobile COVID-19 vaccination unit is set up in the parking lot of the Oxford Casino in Oxford. Credit: Andree Kehn / Sun Journal via AP

A government-run mobile COVID-19 vaccination site in Windham this week will no longer require appointments, a top health official announced Tuesday.

The mobile vaccine clinic, administered jointly by the state and the Federal Emergency Management Agency, launched last week and was billed as a way to improve vaccine access in Maine’s rural areas, which have lagged in vaccinations so far. After initial plans to administer the one-shot Johnson & Johnson vaccine faltered when the vaccine was placed on hold amid concerns about a rare side effect, the mobile clinic switched to the Moderna vaccine last week.

Nirav Shah, director of the Maine Center for Disease Control and Prevention, said Tuesday the clinic would offer vaccines on a first-come, first-served basis without an appointment, a shift in the state’s approach after providers have largely relied on appointments to ensure they do not end up with wasted vaccine doses. Shah said last week that no-appointment slots could soon be offered in Maine.

But patients who made appointments at the Windham clinic will still have priority, Shah said, and people can still schedule appointments by calling 888-445-4111. The clinic is open from 8:30 a.m. to 4:30 p.m. on Tuesday, Wednesday and Thursday this week at 795 Roosevelt Trail in Windham.

Future stops for the mobile clinic include Biddeford, Fryeburg, Turner, Waterville, Old Town, Milbridge, Calais, Madawaska and Auburn. As of Tuesday, more than 623,000 Mainers have received at least one dose of a COVID-19 vaccine, accounting for about 55 percent of eligible adults in the state. But rates still vary widely by county, from 44 percent of adults in Somerset County to 64 percent in Cumberland County.

Appointments at the Windham clinic were largely filled on Tuesday but spots were still available Wednesday and Thursday, Shah said. The walk-up option might not be available when the clinic heads to its next location in Biddeford. Shah encouraged interested people to call when scheduling for that location opens up.

Shah said the walk-up options could benefit people who want to get vaccinated conveniently or who have unpredictable schedules that make setting aside time to schedule an appointment challenging. The state is working with other sites to expand hours and time slots to provide more options.