Kaiser Permanent Workers Represented by Service Employees International Union in California voted for a strike against the health care giant in October.
The move will affect around 1,600 Kaiser workers in Sonoma County, represented by SEIU's United Healthcare Workers West union. Across the state, the union represents nearly 40,000 workers.
Union officials said workers voted for a strike to oppose staffing shortages and low wages compared to other Kaiser regions. But Kaiser called the threat of a strike a trade union tactic aimed at influencing ongoing labor negotiations.
SEIU-UHW's contract ends in October.
Union officials said Kaiser workers in five other states and Washington, DC, are expected to vote to authorize a strike by September. The trade union represents more than 80,000 Kaiser workers across the country.
If approved, union officials said the strike would be the nation's largest walkout since 1
John Nelson, a Kaiser spokesman, said in a statement that the company offers "solid salary increases" and that the average salary for SEIU employees -UHW is "already higher than the market average."