It's 'inevitable' that everybody who has been vaccinated against COVID-19 will eventually need a booster shot, according to Professor Sam McConkey.
The infectious diseases expert says he's also confident the current wave of cases will peak and then 'settle down' over the next month or two.
COVID-19 case numbers have remained stubbornly high in recent weeks, with the five-day moving average still above 2,000.
Meanwhile, there have been growing calls from unions for healthcare workers to get booster vaccines, as many will have received their vaccines much earlier in the year than the general population.
So far, booster vaccines have only been approved for some vulnerable groups and people aged over 60.
Speaking to Newstalk Breakfast, Prof McConkey - head of the Department of International Health and Tropical Medicine at RCSI - said it's now just a question of when's the optimal time to give healthcare workers an additional dose.
He said it's likely that older healthcare workers' protection will have waned more, so they may need to be prioritised.
He observed: “I think it’s inevitable that all of us who’ve been vaccinated as our vaccine wanes will need a booster shot - it’s more a question of optimising when."
Prof McConkey suggested it may be important to offer boosters against any serious new variant of COVID-19 that emerges.
However, he doesn't believe the so-called Delta Plus variant that has recently been detected "is going to be the bad new variant we’re worried about - I think the vaccines should work against it".
Prof McConkey also said he expects the current wave of cases will peak as we head into the winter month.
He pointed to Ireland's very high vaccination rates - although noted Spain and Portugal are now the ‘poster children’ for vaccination rates in Europe.
He doesn't believe the virus will go away entirely, but he does believe it will reach an endemic level.
He noted: “It won’t stop transmitting completely, but it will level out at a low, grumbling level. We’re still at quite a moderate level at this point.
“I’m reasonably optimistic that in two to eight weeks, we’ll find a new way of living with COVID, with enough immunity to stop it continuing to rise.”
Prof McConkey noted that new medicines are now becoming available which should be more effective at treating the virus.
However, he also believes it's now time for any 'late adopters' of the vaccines to get vaccinated.