The Tánaiste says the impact of the Covid-19 vaccine will not be felt until at least April.
Leo Varadkar told his parliamentary party last night there's a good chance the first jabs will happen before the end of this year.
The green light for the Pfizer vaccine could be given by the European Medicines Agency as early as next week.
But Dr Lara Dungan, a leading immunologist, believes there will be no St Patrick's Day parade next March.
Dr Dungan said: “I think that realistically the first people will start getting vaccinations maybe just before the new year in [the Republic of] Ireland, but I wouldn't be breaking my heart for that.
“I think it will take months and months before we can get everybody done, I don't think we'll have a normal March, I don't think we'll have a St Patrick's Day Parade.
“This won't be the type of thing that happens instantaneously, but hopefully by the end of 2021 our population should be vaccinated.”
Meanwhile, the National Public Health Emergency Team (Nphet) will this morning to discuss the “troubling” rise in Covid-19 cases.
It comes after 431 new cases were confirmed last night, as well as six more deaths.
More restrictions are due to be lifted tomorrow, allowing people to travel anywhere in Ireland, and three households to meet.
But former HSE director-general Tony O'Brien believes it should now be reviewed.
Mr O'Brien said: "First of all I think the chief medical officer was right to express those concerns, yesterday's figures were concerning.
“I think it's therefore necessary for Government to consider whether the proposed opening up for the Christmas period, and for the length of time intended over the Christmas period, is still a safe and reasonable thing to do.
“Measures do need to be taken to contain the growth in Covid spread."
