CHICAGO—The Chicago Teachers Union has approved a deal with the nation’s third-largest school district to get students back to class during the coronavirus pandemic, union officials announced early Wednesday. The vote by the union’s roughly 25,000 members ends the possibility of an immediate teacher lockout or strike. The agreement follows months of negotiations—which had intensified in recent weeks—with plans that included more teacher vaccinations and metrics to allow school closures when COVID-19 infections spike. The union said 13,681 members voted to approve the agreement and 6,585 voted against it. In a statement, the union described the agreement as the “absolute limit to which CPS was willing to go at the bargaining table to guarantee a minimum number of guardrails for any semblance of safety in schools.” Union President Jesse Sharkey also criticized the agreement in an email to members that was released by the union. “This plan is not what …