SACRAMENTO, Calif. (CBS13/AP) — A judge on Wednesday blocked an order due to take effect this week that required California prison employees to be vaccinated against COVID-19.

Kern County Judge Bernard Barmann issued a temporary restraining order that prevents enforcement of the vaccination mandate for guards and peace officers represented by a powerful union while the court weighs a request for a preliminary injunction, according to reports.

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The public health mandate due to take effect Friday will still apply to other employees who work in prisons that have health care facilities.

It is aimed at heading off another coronavirus outbreak like one that killed 28 inmates and a correctional officer at San Quentin State Prison last year.

In total, the virus has killed 240 inmates and 39 prison employees since the start of the pandemic.

However, the California Correctional Peace Officers Association opposes mandates for its members. The group has a lot of influence with the state’s Democratic Party-controlled political structure. It contributed $1.75 million to Gov. Gavin Newsom’s successful fight against a recall.

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Newsom has a reputation as one of the strongest proponents of vaccine mandates among state governors. His administration had ordered all state employees, including those in prisons, to be vaccinated or have regular COVID-19 testing.

Yet Newsom was opposed when last month a federal judge ordered that all employees entering California prisons be vaccinated or have a religious or medical exemption. The ruling by U.S. District Judge Jon Tigar did away with an option for prison employees to avoid vaccination and instead undergo frequent COVID-19 testing.

Newsom filed a notice Tuesday that the state plans to appeal that ruling, leaving it in limbo.

On Wednesday, the Sacramento City Unified School District said it was requiring students 12 and up to get the COVID-19 vaccine sooner than the statewide mandate would take effect. Students 12 and older and staff will be required to receive their first or second dose by November 30, unless they submit an exemption.

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The decision comes after Gov. Gavin Newsom announced the nation’s first statewide school mandate that will go into effect once the vaccine gets full approval from the FDA.