People in their 30s can register for a COVID-19 vaccine for the first time from today.
The vaccination portal has opened for those aged 35 to 39, beginning with 39-year-olds on Sunday, 38-year-olds on Monday, and so on.
This cohort will be given their first doses next month, while it is expected people in their 20s will be vaccinated in late July or early August.
People can register online at HSE.ie or by phone on 1800 700 700 and they are being urged to take their appointments.
HSE National Lead for the Vaccination Programme, Damien McCallion, described how the registration process will work.
He said: "In order to register, the quickest way to do that is online.
"What you need is your PPS number, your Eircode, mobile phone number and an email address.
"Once you've registered, we will then be in touch with you over the next couple of weeks, starting from the middle of next week with appointments which will run over the following three to four weeks for that age group, that's the 35 to 39-year-olds."
It comes as 393 new coronavirus cases were reported in Ireland yesterday.
Meanwhile, the Chief Medical Officers in Ireland and Northern Ireland have highlighted their "growing concerns" with the Delta variant.
Dr Tony Holohan and Sir Michael McBride have appealed to the public to avoid activities that may put people at risk of contracting the virus.
In a joint statement, they also reminded those who are intending to travel across the Border over the coming days to be "alert to the epidemiological situation in the relevant local areas".
In particular, the CMOs highlighted their worry about the Delta variant and advised that everyone should remain careful and continue to follow the public health advice.
"Now is a time for continued caution in order to maintain the progress made to date in each jurisdiction, until more people are fully vaccinated," they said.
"People who are not yet protected through vaccination should remain extra vigilant, avoid crowds or large events, meet up with others outdoors where possible and come forward for testing if they develop any symptoms of COVID-19."