The majority of people suffering from severe disease or death as a result of COVID-19 across the world are those who are unvaccinated.
That's according to Professor Luke O'Neill, who says 80% of all deaths and severe illnesses in the US are in the unvaccinated category.
It comes as figures here show 97% of COVID-19 ICU admissions since April have been unvaccinated people.
Of 169 adults admitted to ICU with the virus, just six had been fully vaccinated two weeks prior to their diagnosis.
While out of the 155 recorded pandemic deaths since April, only seven have been people who were fully vaccinated two weeks before they were diagnosed.
Deputy Chief Medical Officer Dr Ronan Glynn is encouraging anyone who is unsure about getting a vaccine to contact their GP or pharmacist for advice.
"Vaccines work. They are about 80% effective at preventing symptomatic COVID-19 disease and they provide approximately 95% protection against hospitalisation - and this protection against severe disease holds up even in the context of the Delta variant", he says in a tweet.
When we see cases of #COVID19 in vaccinated people, we need to remember what we are not seeing. What we don’t see is the very many more infections, hospitalisations and deaths that have been prevented by vaccination. #VaccinesWork @roinnslainte @HSELive @RCPI_news @HSEImm
— Dr Ronan Glynn (@ronan_glynn) August 12, 2021
Prof O'Neill told Pat Kenny an increase in cases was expected.
"It is rising slightly and it is a bit predictable - Delta's much more transmissible, so we saw this coming in a sense."
But he says this is not the main driver to keep an eye on.
"The key metric is severe disease and death, and that seems to be holding firm.
"The main people who are ending up really sick are unvaccinated, and that's holding true across the world now.
"In the US, for example, they reckon 80% of all deaths and severe illnesses are in the unvaccinated.
"There will be some people getting infected who are vaccinated, but it's a minority.
"The advice remains the vaccine is your best protection as ever".
And he suggests that any talk of herd immunity will eventually fall away.
"To be honest it's unlikely we'll get to herd immunity any time soon, and one reason is that Delta is infecting vaccinated people.
"So let's say 20% of vaccinated people are actually picking up infection - and it's only in their noses, they've got minor symptoms - that means it'll be there for quite a while.
"It'll be hard to eliminate then, until you get 100% of people vaccinated all the time.
"I bet there'll be less talk on herd immunity watch because it's going to be much harder to achieve.
"The most important [thing] is just to get a high rate of protection from severe disease... what it means is the virus will become endemic - it will be burning away - for years to come.
"But hopefully won't be harming people because of our vaccinations".