Patients are being warned that GPs will have "zero discretion" in the pecking order for Covid-19 vaccinations amid phone calls to surgeries asking for injections.
Dr Denis McCauley, chair of the Irish Medical Organisation's GP committee, said anyone who is not on the priority list to be vaccinated will be told "no" and that discretion shown in the past in relation to flu vaccinations will not be repeated.
"The vaccines will be given out as per the risk groups, with zero discretion to give to any other groups," he said.
"We want to do this efficiently, ethically and quickly.
"If someone who is 85 comes in and has an elderly carer but the carer doesn't fit the criteria, are we going to give them the vaccine? No, we can't.
"We have to be very tight on this. This is a very finite resource."
Discretion shown in the past with regard to the flu vaccine could not be applied with the Covid-19 vaccine, he added.
"That's not going to happen this time. We intend to do this as ethically as possible so we do need people's understanding."
Dr McCauley said GPs are in the process of drawing up lists, according to priority groups, of who they will vaccinate.
The Oxford-AstraZeneca vaccine will be supplied to GPs in batches of 100.
Concerns raised over distribution issues that arose with the flu vaccine earlier this year are being addressed with the cold chain supply service.
The only limiting factor to accelerating the national roll-out, said Dr McCauley, will be the supply of vaccines coming into the country.
"If the supply is there, we hope to help accelerate the national roll-out," he said.
"We are used to giving vaccines. If a million vaccines are distributed to GPs in the middle of February, let's just say by St Patrick's Day we will be looking for more."
It is understood the requirement for a 15-minute observation period after receiving the Oxford-AstraZeneca vaccine could mean some GPs will have to reconfigure their surgeries to create space.
"The supervision period after the AstraZeneca vaccine is still being looked at," said Dr McCauley.
"In the UK there have been so few problems with it that they have dispensed with the 15-minute observation period, but I imagine there will be a more careful approach here in the beginning.
"We are starting at the 15-minute period - but if the European Medicines Agency says five minutes, all the better.
"The actual space needed to do the injection is very small. Everyone will have their owns solution but one recommendation is that the injection is given in the waiting room and the observation is completed in a consultation room.
"There are ways and means around it."
Dr McCauley said GPs were already receiving calls from patients asking them when they could receive the vaccine.
"We know there is huge interest in getting this vaccine, but we need people to be patient," he said.
"We will be contacting patients in due course to invite them to be vaccinated and we will waste no time once we have vaccines in our fridges."