Some 37,000 employees of the University of California started a two-day strike on Wednesday, months after rejecting the latest offer.

The strike across 10 campuses, five medical centers, and labs came as a result of what the service and patient care workers union alleges is unfair bargaining. The American Federation of State, County, and Municipal Employees Local 3299 union filed a complaint to the Public Employment Relations Board when UC raised premiums by 2% and copays by 50%, among other changes, for the next contract without informing its employees.