The Director of the National Virus Reference Laboratory at UCD, Dr Cillian De Gascun has urged people who have not yet had their booster vaccine to do so as it will continue to protect against serious illness and hospitalisation, despite changes in the virus itself.
Dr De Gascun said that while the BA4 and BA5 variants now account for 85 per cent of cases in Ireland, the vaccines available were still working.
"It's important to try to reassure people that while these viruses have a growth advantage and are more contagious than BA1 and BA2, it's a minor change in behaviour, we're not going back to a previous virus like Alpha and Delta."
Dr De Gascun said that scientists needed to continue to monitor Covid figures, to see how many people were being admitted to hospital with the virus as it is continuing to put pressure on the system.
Trying to ascertain disease severity at a time when testing policies globally have changed is quite challenging, he added.
"There are other things we can do - look at how the virus is behaving in cells, the viral load, we can do some animal model work and, generally speaking, at the moment it's probably too early to definitively rule out the fact that these viruses might cause a more severe disease.
"At the same time there are no red flags at this stage. There are no major causes for concern."
At some point in the future the vaccine will have to be changed to match changes in the virus, Dr De Gascun said, adding that Covid was not the same as influenza which evolves at a far faster rate, meaning flu vaccines have to change from year-to-year.
!The vaccines that we have at the moment (for Covid) are still very good," he added.