A US pharmacist has been jailed for three years after pleading guilty to tampering with hundreds of Moderna coronavirus vaccines, the Justice Department said on Tuesday.

Steven R. Brandenburg, 46, "purposefully removed" vaccine vials from their refrigerator unit even though they must be stored at a certain temperature until used, court documents said.

The pharmacist was also ordered to pay $83,800 in compensation to the Wisconsin hospital where he worked.

He removed the vials on two overnight shifts in December, leaving them outside for hours before returning them to be used on recipients the following day.

A total of 57 people received vaccines with the vials that Brandenburg had tampered with, the Justice Department statement said.

"The purposeful attempt to spoil vaccine doses during a national public health emergency is a serious crime," said Brian Boynton, acting assistant attorney general of the department's Civil Division.

Brandenburg had expressed skeptical views about vaccines and specifically the Moderna vaccine, according to his plea agreement.

Moderna vaccines must be stored at standard refrigerator temperatures.

More than 124 million doses of the Moderna vaccine have been administered in the US.

The two-shot regime is around 90 percent effective against symptomatic COVID-19 and 95 percent effective against severe disease.