Nurses at two medical units in Tipperary have voted in favour of industrial action.
The Irish Nurses and Midwives Organisation said nurses working at St Patrick's Hospital Iin Cashel and St Anthony's Unit in Clonmel voted "overwhelmingly" in favour of industrial action.
The INMO said the type of industrial action is still to be decided upon, but it may include a full withdrawal of nurses from the two sites.
Meetings have been held in recent months with management where nurses outlined their concerns over the provision of acceptable care to vulnerable patients and also requested additional staff.
Nurse representatives are due to meet management again tomorrow.
Following the outcome of the vote, INMO Industrial Relations Officer Mary Fogarty said: "INMO members are forced into this dispute which is not for themselves, but for their patient population who are elderly, frail and vulnerable. Nurses have a duty to advocate to the HSE on their behalf.
"The current nurse staffing levels are inadequate across all shifts. When we meet HSE officials tomorrow we will expect an action plan for the filling of all nursing vacancies. A failure to provide such a plan will make industrial action inevitable."