(AP) — Mississippi has given COVID-19 shots to thousands of state prisoners in its ongoing mass vaccination effort behind bars, state officials said.

The Mississippi Department of Corrections began the effort with the state’s most populated prison — Central Mississippi Correctional Facility in Pearl.

By Friday, officials said they had completed vaccinating nearly all 3,017 inmates there.

Inmates in the Mississippi State Penitentiary at Parchman will be vaccinated this week, and those in South Mississippi Correctional Institution are scheduled for next week, the agency said.

The vaccinations are not mandatory for inmates. Some states have had as many as 40% of inmates refuse the vaccine, Mississippi has only experienced about 1% refusing it, the agency said.

Mississippi has a population of about 3 million. Gov. Tate Reeves said Monday that the state has administered more than 1 million vaccinations to the general public. Many of the shots have been given at drive-thru sites run by the state Health Department and the Mississippi National Guard.