Professor Sam McConkey says a widespread booster vaccine programme 'tomorrow' is unlikely to bring down COVID-19 cases in the medium-term.
He was speaking as the Cabinet Subcommittee on COVID-19 meets later to consider recommendations from NPHET.
The wider use of Digital COVID Certificates, antigen tests and a return of the work-from-home policy for non-essential workers are among the measures set to be discussed.
Prof Sam McConkey, from the Royal College of Surgeons, told Newstalk Breakfast vaccines are not protecting as much against transmission.
"Unfortunately we're now discovering that the vaccine alone is not enough to control COVID in Ireland and we won't.
"Loads of [people] would love to go back to 2019 ways of socialising and enjoying ourselves.
"But if we do that at present, we're realising that the virus will start spreading more - and is spreading more.
"It's finding a new normal: it's this definition of what is new, what is the way of socialising and physical interaction for 2022?
"We're just slowly discovering that".
But he says boosters are unlikely to fix things in the medium-term.
"I don't really believe that a big booster programme tomorrow would solve this problem for us.
"I know that would be a nice thing if it did.
"This vaccine is more a vaccine against disease - and severe disease and death - than a vaccine against transmission.
"This particular vaccine... it doesn't provide immunity in your nose to stop you catching it - and unfortunately stop you passing it on to the people around you as well as it does to prevent disease and death.
"It's unlikely that the vaccine - even if we boosted everyone tomorrow - would just sort of fix the problem.
"It might improve it for a month or two, but it's not really a definitive fix".
Prof McConkey has previously said everyone in Ireland will need a booster, but we should wait for the 'next generation' of vaccines.
Antigen test costs
He says for the moment, the answer is to socialise less.
"It's keeping the number of people we meet smaller than it was in the last six weeks.
"It's clear, since the beginning of October, the numbers of COVID are increasing.
"They were increasing about 5% a day there for a while, and now maybe 2% a day: so that's unsustainable.
"If you just continue that it'll just get bigger and bigger and things will get worse."
On the cost of antigen tests, Prof McConkey says they need to be down to about €3 each to make them viable.
"You have to use them two or three times a week a least - so you're then at 100 or 200 tests a year.
"So if you're thinking about a reasonable cost per year for this health intervention, is €400 or €500 a year too much?
"That works out about €2 or €3 each - so if you're using them two or three times a week, it has to be cheap to be affordable to keep that going for six months or a year".