Everyone over 70 is set to get their first dose of a COVID-19 vaccine by mid-April, the HSE's Chief Clinical Officer has said.
Dr Colm Henry said that means the vaccination process - due to begin from Monday - for that group should be concluded by mid-May, as there's a 28-day gap between the two doses.
Supply issues have led to some delays in the plans to vaccinate priority groups over the coming weeks.
That was further complicated by the recommendation that over-70s should receive the Pfizer and Moderna vaccines where possible over the AstraZeneca one.
The AstraZeneca vaccine had been a key part of plans for the vaccination of older people, and Dr Henry told Newstalk Breakfast officials had to adapt 'in mid-flight' last week.
However, he said work is now underway to administer the two mRNA-based vaccines to older people in GP clinics and dedicated vaccination centres.
He said: “It’s a two-dose vaccination, and we’ll have the first dose complete in this by mid-April - four weeks later is the second dose.
"But there’s more evidence coming through that even after that first dose, people get protection from the most serious effects of that illness."
The WHO and EMA have now both said the AstraZeneca vaccine can be safely administered to over-65s.
However, Dr Henry said the approach here isn't going to change at the moment.
He said: “What we’re doing is interpreting existing evidence, which just shows there’s a lack of evidence at this point in time in older age groups.
“Older people need to get that vaccine which is proven, based on today’s evidence, to give the best chance of giving them protection. That’s why we’re giving the mRNA vaccines to older people."
'Shock' to hospitals
Dr Henry also warned it'll take a long time for hospitals to recover from the "shock" of the third wave of COVID-19.
The number of people with the virus being treated in hospital has fallen to 984, with 167 in intensive care units.
Health officials say the numbers in hospital could drop to between 200 and 400 by the end of the month based on current trends.
However, Dr Henry said it will be a slow recovery for patients already being treated.
He said there's been a big drop in hospital numbers over the last week, with numbers down a quarter.
He also noted the five-day moving average of new cases and 14-day incidence rate are 'certainly moving the right way'.
However, he observed: “It’s a slow recovery in hospitals, because people take so long when they’re in there [to recover].
“It’s going to take a long time for our hospitals to recover from what was a shock in January.”
Dr Henry said the situation over the last few months has been 'dizzying' in Ireland, and it shows why the country can't lose focus.
He said: “Over the past two months we’ve gone from being the best in Europe, to the worst in Europe, to the fastest improving in Europe.
“We’re top of the league, to the bottom of the league, to the middle of the league, all in a two-month period. Things can change very quickly.”