A state appeals court judge has reversed a lower state court's ruling that upheld Boston's COVID-19 vaccine mandate for city workers. The policy required municipal employees get vaccinated against COVID-19 or risk termination, and it eliminated an earlier provision that allowed unvaccinated workers to instead undergo weekly testing.

Mayor Michelle Wu announced the policy on Dec. 20, less than two weeks after striking an agreement with city worker unions Dec. 7 that continued the testing opt-out provision.

Three unions — the Boston Police Superior Officers Federation, the Boston Police Detectives Benevolent Society and the Boston Firefighters Union Local 718 — argued Wu had violated their Dec. 7 agreement and state collective bargaining law. They filed for a preliminary injunction to pause the policy and lost when the lower court ruled against them.

Justice Sabita Singh on Tuesday issued an 18-page ruling that sided with the unions and overturned that decision. Singh also put in place a preliminary injunction that prevents Boston from acting on this policy "until final resolution of this matter."

In the decision, Singh said the lower court judge failed to properly weigh several factors that were relevant to a request for preliminary injunction.

The ruling came hours after Wu said at a press conference that the remainder of the vaccine mandate policy, which currently requires people aged 12 and up to present proof of vaccination to enter most indoor recreation venues, could be rescinded in a matter of days as Boston’s critical COVID-19 metrics trend downward.

The mayor's administration said it is "disappointed" in the decision and is carefully reviewing the ruling.

“To protect communities and workplaces against COVID-19, courts across the country have repeatedly recognized the rights of state and local governments to require public employees to be vaccinated," a spokesperson for the mayor said in a statement. "More than 95 percent of the City’s workforce is vaccinated because of the policy we enacted. Our workers and residents who rely on city services deserve to be protected."