The general-secretary of the Teachers' Union of Ireland (TUI) has said its members will decide on any move towards strike action when it meets this week.
The TUI is to hold its annual congress on Tuesday and Wednesday, amid a revised vaccination rollout based on age and not profession.
Michael Gillespie told Newstalk Breakfast his members will consider their options.
"Our congress starts tomorrow and it goes on virtually Tuesday and Wednesday, and it'll be our members that will decide that.
"We expect there to be emergency motions about this issue that arose long after we'd finished the agenda.
"It only occurred last Tuesday where teachers who thought they were being prioritised in terms of essential workers - they weren't expecting to be ahead of anybody.
"They were at number 11 after the Guards, who were at number 10, and they were expecting - like what's happening in other jurisdictions - to be vaccinated parallel to the main body rollout because they are essential workers".
'No safe vaccine for under-18s'
He said the re-opening of all schools on April 12th will see teachers working in the most crowded classrooms in Europe.
"Teachers will be in classrooms, crowded classrooms - the most crowded classrooms in Europe, still - where the children won't be vaccinated and can't be vaccinated because there's no safe vaccine as yet for under-18s.
"If a teacher gets COVID, a teacher's out for 14 days... in a post-primary school that interrupts education for two weeks for people.
"The problem is that - because of previous Government [sic] - we have a scarcity of teachers, there's a recruitment and retention problem, so we don't have substitutes to replace those teachers.
"Teachers were not expecting to be vaccinated by the 12th of April, but at least they thought they knew where they were on a list - even though they didn't even know the time of it - now they're not on the list at all".
'If you want to keep schools open, vaccinate them'
Mr Gillespie added that vaccinating teachers would ensure schools stay open.
"If you can vaccinate teachers then you protect the sustainable re-opening of schools, once they're vaccinated.
"The Government has stated continuously that one of the things it wants to open up fully is schools.
"If you want to keep schools open, then you vaccinate them.
"There is a huge difference between someone who's working from home at the age of 40, and someone who's in front of 25 students - or meeting up to 250 students - and therefore mixing with 250 households every day".
The union also said that a "very large number" of members has contacted it to express their "deep concern and anger" over changes to the vaccine rollout.
The union said the move "completely undermines the confidence of teachers in the Government's commitment to re-opening schools in a safe and sustainable manner."