A leading health expert has called on the Government to open the vaccination registration portal to all ages.
Pharmacies will start to offer the single-shot Johnson and Johnson jab to the over 50s from Monday.
Deliveries of around 60,000 vaccines are expected at around 1,300 participating outlets.
On top of that, registration is expected to begin for those aged between 30-39 next week.
But Liam Fanning, Professor of Immunovirology at UCC, has said the portal should be open to "anybody and everybody".
There is an urgency around vaccinations at the moment as the dangerous Delta variant is strengthening in the UK and Ireland.
Speaking to Newstalk Breakfast, Professor Fanning said: "These vaccines have been shown to be wonderfully effective against all variants so far.
"The one exception is [that] one shot of the AstraZeneca vaccine leaves you more or less unprotected - you need the second shot.
“Those who are waiting on the AstraZeneca second shot… give them Pfizer and Moderna, and open the portals to the under-40s.
“Just stop this age-related stuff - the death rates in the under 40s are more or less similar to those when you get down to under 16s.
“There’s every reason why one should open up the vaccine portal to everybody and anybody over 16.
"Obviously, it’s over 18 for Moderna, but 16 for Pfizer.”
On the issue of antigen testing, Professor Fanning added: “If everybody arrived into this country and were given four antigen tests… that would cover them every second day for eight days.
"Make this as easy as possible: if you give people antigen tests, they will use them.”
