Pharmacies have begun vaccinating people aged 18 to 34 against COVID-19.
Some 120,000 Johnson & Johnson jabs will be distributed to chemists over the next week.
It could lead to all adults being protected against coronavirus as early as the end of August.
Eleanor Spooner is pharmacist and co-owner of Spooner's CarePlus Pharmacy in Templeogue in Dublin.
She told Newstalk Breakfast they are starting straight away.
"When the announcement was made on Friday we pretty much were swamped with calls all day long.
"I'd say it could have been 100 to 200 calls in the whole day.
"We were caught off guard, but at the same time we're absolutely delighted now to be able to take part and be able to vaccinate this cohort.
"We were busy all weekend booking in our appointments and trying to get prepared and organised for this morning.
"We intend to vaccinate 40 people today with what we have left in our fridge of the Janssen vaccine.
"We said we'll get going straight away now that we have the thumbs up.
"Our only thing now is that we'll have run out by the end of the day today - so we're hoping to get another delivery of Janssen later in the week."
'Order and fairness'
She says they have a full staff, with each vaccine dose taking around 45 minutes.
"It's a process - first thing you have to do is prepare the vaccine, then obviously take your time to discuss things with the patient, and administer and then there's observation afterwards.
"We did prepare to have enough staff for this happening... we're telling patients to allow 45 minutes in the pharmacy for the whole process."
Asked about how they will manage different age cohorts, she says they are working from the top down.
"We've been given very specific guidelines by the HSE, and up until now we were only allowed vaccinate those over 50 years of age.
"We haven't been told 'we start at 18 or do we start at 34' - so until we're told otherwise we're going to work at 34 down.
"We'll just look after the people who are coming our way.
"We feel the fairest way to do it is by date of birth and work our way down - we haven't been specifically told by the HSE that we need to start at the 18-year-olds.
"We need to have some order to it and some fairness to it, and we feel this is the best way to do it".