Professor Luke O'Neill says everyone aged 60 and over in Ireland should receive a third, or booster, shot of coronavirus vaccine.
Under current plans, residents aged 65 years and older living in long-term residential care facilities - and those aged 80+ living in the community - will be offered a further dose.
And those who are immuno-compromised will also receive an extra dose.
Prof O'Neill told The Pat Kenny Show new data is looking very positive.
"The Israelis have measured people after their third shot: they get a 10-fold higher antibody level than after the second shot.
"So the booster really drives the immune system hard... So it looks like as if they may become a three shot vaccine.
"People ask me what's the best analogy for this? It's like a manager getting the players on the field is the first shot.
"The second [shot] is that he shouts at the team to tell them to play harder, the third shot he roars at them.
"In some people, the team begins to get a bit sleepy and if you're older - for instance - maybe it goes off the ball so the third shot will be needed for certain groups".
And the Trinity College immunologist says older people should be prioritised, as they mainly received AstraZeneca.
"What's very important for us - and I think this is a very clear message we should say - everybody over 60 in Ireland should be given the booster shot, cause they've mainly had AstraZeneca.
"Of course it was forced on them egregiously, and we were all saying 'This is unfair on the over 60s' give the over 60s a booster."
'I'd be optimistic'
He says evidence shows AstraZeneca wanes more quickly than Pfizer.
"The vaccines are still giving some protection at the moment, but the sensible thing to do is to give boosters - especially for everybody over 60".
And he says with such levels of efficacy from a third shot, eradication of COVID-19 could be a possibility.
"That's a prospect: if the third shot is shown to be fantastically effective, transmission will stop in the community.
"No virus will grow in you if you have a third shot, so there is a prospect of really driving down.
"I'd be optimistic about that one".
Earlier this month, the HSE's Dr Colm Henry said "time will tell" if everyone in Ireland will need a COVID-19 vaccine booster.
He explained: "Time will tell. I know it's a frustrating answer for people to hear, but we do rely on the evidence.
"We want to make sure it's safe - and it appears giving a booster is safe in the groups we mentioned.
"We need to know it translates into immunity that means something."
