The Big Apple’s largest police union told its members Wednesday that it would sue the city if cops are required to get the COVID-19 vaccine, The Post has learned. “If the City attempts to impose a vaccine mandate on PBA members, we will take legal action to defend our members’ right to make such personal medical decisions,” Police Benevolent Association President Patrick Lynch wrote in an email. The announcement comes on the heels of Mayor Bill de Blasio’s announcement requiring all New York City school staffers to get the jab. “As of this writing, the City has not indicated whether it will attempt to impose vaccine mandates on other city workers, including police officers,” Lynch added. The message to its members, obtained by The Post, is the first public comment the PBA has made about mandating the vaccine since cops were able to get immunized. The NYPD was one of the first groups eligible for the vaccine in January after all the city unions banded together and lobbied for cops to jump up in line. NYPD officers, though, have been hesitant to get the jab — with the latest figures showing only a 47 percent immunization rate among the entire uniformed and civilian workforce.