On Thursday, 40,000 booster jabs were administered despite hundreds of people being turned away from some walk-in centres in Dublin after they reached capacity.
Taoiseach Micheál Martin, Tánaiste Leo Varadkar, and the HSE have all apologised over the issue.
Speaking to Newstalk, former HSE director-general, Tony O'Brien, said there are lessons that need to be learned.
"They're effectively suffering with consequences of trying to do something that was quite good which was give people much more choice and self direction, as it were, compared to the first round of boosters where typically you simply got a text having registered and that text told you to go to a certain place at a certain time," Mr O'Brien explained.
"They wanted to make it a bit easier, give people more choice. Hasn't worked out quite as intended, so they're having to regroup and change a few things."
This comes after concerns were raised last week over the number of people turning up to get booster jabs.
Mr Martin told the Dáil on Tuesday in the week beginning November 22nd, 208,000 appointments were made, but about 80,000 people turned up to receive their booster shot.
Last week, 180,000 appointments were made, but only 93,000 people turned up.
On Friday, a number of walk-in booster clinics will operate across the State.
🧵 Here are today's walk-in #COVIDVaccine clinics. We're operating some walk-in clinics for dose 1 and dose 2, and booster vaccines for healthcare workers and people aged over 50. #ForUsAll pic.twitter.com/JMlWIdZiW7
— HSE Ireland (@HSELive) December 10, 2021