Ireland should have started rolling out COVID-19 booster vaccines earlier, an immunologist says.
Professor Christine Loscher believes the country's now "on the back foot" when it comes to additional shots.
She was speaking as COVID-19 case numbers and hospitalisations continue to rise.
Around 3,000 new cases have been reported daily over the past week.
25,000 cases were reported last week, which is the third highest since the pandemic began.
Latest figures also show there are 551 patients with the virus in Irish hospitals - the highest figure since February.
Currently, boosters are being administered to healthcare workers, over-60s and immunocompromised groups.
However, Professor Loscher - Professor of Immunology at DCU - believes the booster programme should've started rolling out quicker than it did.
Speaking on Newstalk Breakfast, she noted that the majority of people ending up in hospital are over-55s.
She said: “The one way of addressing that and hopefully having an impact on our hospitalisations and ICUs is getting that booster programme fast-forwarded.
“I think we’re on the back foot with boosters - I think we’ve missed our window of opportunity.
"We should have been rolling out and followed the science earlier on boosters.
“We’re not just dealing with healthcare workers and people over 60. We’re also dealing with a population of people that predominantly got AstraZeneca - the science will say that’s probably going to wane a bit faster, and we know it’s not as good against Delta."
Professor Loscher said the booster programme should have been ready to go as soon as the National Immunisation Advisory Committee (NIAC) made its decision on boosters.
She said "we are where we are now", but it's important to "press fast-forward" and get boosters rolled out as quickly as possible.
Meanwhile, Health Minister Stephen Donnelly told the show about 1.3 or 1.4 million people will receive boosters under the current criteria.
He said the 'standard' gap between a second vaccine dose and the booster is now being reduced from six months to five months.
He said: "We are moving through the groups quickly, and it's really important to say it appears to be having a very positive effect.
"The one age group where the cases and hospitalisations are falling... is the over 85 group. We believe that's a combination of behaviour and the boosters."