The Health Minister says people aged under 30 could be vaccinated against Covid-19 earlier to reduce transmission of the virus.
Stephen Donnelly has asked the Department of Health to examine the possibility of revising the order of age cohorts.
It means people aged 18 to 30 would get their jab before those aged 30 to 50, once people in their 60s are vaccinated.
Some senior officials fear there will be a spike in cases among younger people once society begins to reopen.
Kingston Mills, an immunology professor at Trinity College Dublin, thinks it makes sense once the vulnerable are protected.
"The person who is aged 49 and is working from home is not coming into contact with many other people and is very unlikely to get infected," said Prof Mills.
"This is versus the 25-year-old who is working in a meat factory or living in a high-provision centre or in some other situation where they are at seriously high risk of becoming infected.
"If you want to stop transmission of the virus, you immunise the population at highest risk of getting infected."
From this morning, 67-year-olds can book their Covid-19 vaccination appointment.
They can register for appointments through the HSE website and phone line.
The Tánaiste is being accused of causing anxiety and stress to the latest group of people registering for vaccination against Covid-19.
Wexford Councillor Michael Sheehan has hit out at Leo Varadkar for saying people who refuse an offer of AstraZeneca will go to "the back of the queue".
Mr Varadkar warned anyone who refuses an AstraZeneca vaccine will have to wait until the entire population is vaccinated to be offered an alternative.
"They would have to wait until the end, and it's not possible to know when the end would be but it wouldn't be June or July, it would be later than that," said Mr Varadkar.
"The best option is the vaccine that's offered to you, and all the vaccines are effective and they're safe for the age groups they're indicated for."
Councillor Sheehan said it was a poor choice of words and has only served to compound fear and anxiety for people.
He said that people have been ringing him to say they are uncomfortable going for the AstraZeneca vaccine but then are worried that they will be left behind if they don't take it.
"I think that is unfortunate and I think it is the wrong way to behave," said Cllr Sheehan.
"It's the wrong statement and it's the wrong message to be putting out to people who are in either an anxious or a vulnerable state."