More than 200 workers at Pfizer's plant at Ringaskiddy in Co Cork have voted for industrial action over changes to the company's employee pension scheme.
The ballot was taken following a decision by the company to hire 20 new operators in Cork in 2015 under a new proposed pension scheme rather than the existing defined benefit scheme.
In a statement, SIPTU Sector Organizer Alan O'Leary said new employees should be treated in the same manner as existing ones unless there is an agreement on any change.
Since 2014, the company has been trying to introduce a defined contribution scheme for 900 of its 3,300 employees.
These workers are employed at the company's oldest operations in the country, at Ringaskiddy and Little Island in Cork, and also include office staff in Dublin.
Under the proposals, the 900 staff at the Ringaskiddy and Little Island plants - together with 100 Dublin office staff - would retain the rights to a guaranteed pension already built up, or accrued.
Pension benefits for any future service would be paid into the new defined contribution arrangement.
The issue has been before the Labour Court twice. In November the court recommended that both sides engage in a 12-week process to reach agreement. This has yet to take place.
Pfizer says it cannot afford to sustain what it is paying into its defined contribution scheme and that it is impacting on the competitiveness of the Irish operation.