Re-introducing mandatory facemasks on public transport may not make any difference to the spread of coronavirus.
That's according to Liam Fanning, professor of immunovirology at University College Cork (UCC).
He was speaking as Health Minister Stephen Donnelly suggested it could be re-introduced on public transport and in shops.
On Friday, there were 537 people in hospital with the virus - 27 of whom were in Intensive Care Units.
The Irish Nurses and Midwives Organisation (INMO) has called for a return to mandatory mask wearing on public transport.
But Prof Fanning told Newstalk Breakfast: "No, I don't think we need mandatory masking."
He believes it may not make a big difference "given the current infection trajectory that people experience when they have COVID-19."
"It's very very hard to quantify the actual impact of masks.
"The certainty is that wearing masks does probably reduce the transmission, or you picking up, COVID-19.
"This virus is so infectious at this stage that the capacity as we wear masks... you see a few people that are wearing masks at the moment.
"Some of them are still under the nose, some of them are not tight enough.
"The actual seal that you have on most masks now is probably not sufficient to effectively cut down on transmission".
And he says: "I think there's some comfort for people when they're wearing a mask, but it's not a shield.
"And back to the old messaging of 'Get your vaccine'".