The head of the HSE says a further fix has been put in place to try and combat multiple booster appointments.
Paul Reid was speaking after the health service confirmed people were being offered several appointments due to an issue with the vaccine programme's IT system.
In a statement, the HSE said earlier that patients were being offered HSE booster appointments after they have already been jabbed at their GP or pharmacy.
It said GPs and pharmacies operate on different systems to the HSE programme – and it can take as long as two days for one system to notify the other.
While some people were turned away at a vaccination centre in Dublin owing to 'very large queuing times'.
Mr Reid told The Hard Shoulder the system has been updated.
"It's not an IT system issue, but certainly there can be delays between GPs being under pressure - some of them sometimes not upload it immediately - but they are doing a phenomenal job for us.
"And secondly pharmacies - that system does update in real-time.
"What we've had to do to address that, where somebody may have got an appointment for themselves and go somewhere else, we've now put in a text process where people can respond to us."
He says this contains three options: people can seek a new appointment, reject the appointment or that they had COVID-19 within the last six months.
Asked about some people who texted 'Reject' and still could not resolve the issue, Mr Reid says a new fix has been provided.
"We put in a further fix last night, where the third option there and COVID is on it to address that.
"We are taking all of those returns at the back-end and then removing appointments."
But Mr Reid says he understands how frustrating this is.
"I acknowledge and fully understand it's been frustrations [sic] at the start of this.
"But just as I stand back, we do want to get as many people as we can as quick as we possibly can.
"We have had 22 centres operating today, fully acknowledge the issues around UCD".
And Mr Reid says the long queues, in a way, could be seen as a good thing.
"People want to come forward and they want to come forward this quickly.
"I've never said that there's vaccine hesitancy, I've been asked that question a few times".
Mr Reid says more than 1.1 million people have now received a booster shot.