Minister of State for Older People, Mary Butler, says 'nobody will be left behind' in the country's vaccine rollout.
She was speaking following appeals on Lunchtime Live on Thursday from older people seeking clarity on the plan.
Richie from Tallaght in Dublin, who is over 70, said: "We were to get it [in] February, then it was March, now the last I heard on the radio the other day was May."
"So we don't know whether we're coming or going, we can't get anything definite - the HSE says one thing and the [Health] Minister says another thing."
"We're lost, we don't know where we are, we don't know what we're getting, we don't know what's happening."
Minister Butler told Lunchtime Live on Friday that they will all be vaccinated by mid-May.
"I want to put some clarity now for the over-70s so they know exactly what's happening.
"From Monday next, which is the 15th, vaccination will commence to all over-70s.
"We're starting with the over-85s and this vaccination will be done through their GP practice."
She said these people will be contacted by their GP practice.
When those aged 85 and over are vaccinated, the next cohort will be those aged 80-84, followed by 75-79 and then those aged 70-74.
Acknowledging it will be a number of weeks before all the groups get vacinated, she added: "You have to start some place, and we have to start with the most vulnerable".
"To date, the majority of 85 and older have been contacted by their GP - and [HSE CEO] Paul Reid confirmed yesterday that 12,000 vaccines will be delivered next week for over-85s.
"We've approximately 72,000 over-85s in the country, so for the next three weeks the emphasis [is] on age 85-plus", she said.
'Limited by supply'
She also said there will be "a huge cohort" of people in nursing homes who will recieve their second vaccine next week.
"Our problem is, Andrea, that we are limited by supply."
Overall she said she is hopeful that those aged 70 and over - of which there are 490,000 people - will be vaccinated by mid-May.
But she added this is "purely driven by supply, the amount of supply we'll get into the country".
"We would love to have all the supply we need, but unfortunately we don't.
"But by April, we expect to have one million vaccines a month, and it will significantly ramp up in April and May.
"But for the first quarter of this year it will be slower".
Deputy Butler said 84 practices across 20 counties will be receiving 12,000 vaccines next week.
She said up to Tuesday of this week, the country has received 272,000 doses - of which 244,000 have been administered.
"You always have to keep a small buffer for the second vaccine - because for anyone who would have got the [Pfizer-]BioNTech vaccine, they have to receive their second dose within 28 days.
"So we have to make sure that you have that small buffer, so that we won't lose out on that timeline".
"Nobody will be left behind, everybody who wants the vaccine will get the vaccine".
She added that plans are being finalised to allow people, who are unable to leave their home to receive the vaccine, to get the jab.
She said anyone who may not have a GP should register through the HSE Helpline on 1850-24-1850.