A public health expert says he believes a fourth wave of coronavirus infection has begun.
Professor Sam McConkey was speaking as the latest available daily figures show the number of cases reached the highest in more in than two months.
Some 562 new cases of the virus were reported on Sunday, more than any day since May 1st.
While the numbers in hospital increased by six in 24 hours to 48, 14 people were being treated in intensive care.
Prof McConkey says he is hopeful the impact will not be as large as before.
"My views for the last 15 or 16 days cases have gradually started to rise, we've an R [number] currently of about 1.2 - and this is the beginning of a fourth wave.
"I'm hoping, having said that, that it will be much much less traumatic to us as a country and as individuals here than the previous first, second and third wave.
"I'm hoping that, following the UK, there'll be much less hospitalisation, much less ICU admission and hopefully much less rate of death".
But he says more variants other than Delta will have to be tackled, and may pose a risk to vaccinated people.
"There will be more variants after this Delta variant; there's no reason to think the Greek alphabet will end at Delta - there will be new ones in the future.
"The one I really fear is one that transmits widely in vaccinated people and where the vaccine wouldn't work.
"It would take three to six months for the vaccine companies to make a 'version two' of the vaccine, and for that to get created and billions of doses distributed to boost us against the new variant.
"So I think this is a long-term virus".
'All options' being looked at
It comes as CEO of the HSE, Paul Reid, said there is currently no plan to prioritise the vaccination of teenagers ahead of the return of schools in September.
However, he added that "all options and scenarios" are being looked at when it comes to rolling out COVID-19 vaccines to 12 to 15-year-olds.
Speaking to On The Record with Gavan Reilly, Mr Reid said the HSE will follow the NIAC recommendations when it comes to inoculating this cohort.
"NIAC are assessing the evidence and information relating to the vaccination of 12 to 15-year-olds, they're considering that over the next short period, they haven't made any recommendations as yet," he said.
"What we are doing in parallel is looking at various scenarios that may emerge for vaccinations of younger children, 12 to 15.
"We would look at it in the context of the various channels for vaccinations that we have now, GPs, pharmacies and vaccination centres so we're looking at all options and all scenarios but ultimately, it's still under assessment by NIAC.
While it had been reported today that the vaccination of children in that group could start as early as next month, Mr Reid stated that extending the rollout to this cohort was "not currently built into baseline assumptions".
Meanwhile, pharmacies are due to begin administering the Johnson & Johnson COVID-19 vaccine to people aged 18 to 34 from today.
Latest vaccination figures show by Tuesday, more than 50% of the adult population will be fully vaccinated.
There have been 4.4 million doses administered to date, according to Professor Brian MacCraith - chair of the High-Level Task Force on COVID‐19 Vaccination.
By tomorrow, >50% of our adult population will be fully vaccinated
~4.4M doses administered to date
>343k doses administered in the past week
>55k doses administered on each of 4 days
>103k AZ dose 2s administered last week
Janssen for 18-34s starts today
— Brian MacCraith (@muirtheimhne) July 5, 2021