The chief executive of the HSE has insisted most walk-in booster vaccination centres are “running smoothly” despite long delays at several sites yesterday.

Paul Reid described yesterday as the most successful day in the booster campaign so far, as over 40,000 people received their third jab and now over 1.1 million people have received three doses of the Covid vaccine.

His comments come as yesterday morning the HSE told the public that the Covid-19 walk-in booster vaccination centres at Croke Park and UCD were at full capacity, with long waiting times in several other centres also.

Today there was a 90-minute queue in Dundalk, a 30-minute queue at Clonguish in Longford, an hour at City Hall in Dublin, over an hour at WIT in Waterford, an hour in Roscommon, and 30 minutes in Offaly, the HSE said in an update.

Speaking today, Mr Reid said an appointments system is still being used in conjunction with the walk-in centres.

“We’re doing it quite differently this time. So, we are running multiple groups of ages and healthcare workers at the same time. We are giving people an opportunity of multiple channels,” he told RTÉ’s News at One.

“We are still doing appointments but we’re doing appointments in parallel with walk-in procedures… I fully acknowledge the issues that we had in relation to UCD. We had 23 centres running yesterday. The vast majority all ran very smoothly and a good experience for people going through them,” he added.

Mr Reid said the health service’s goal is to get as many people boosted as quickly as possible and walk-in centres will operate for longer periods of time to avoid a repeat of yesterday’s issues.

He argued that Ireland is still outperforming many European countries in terms of the booster roll-out and stands fourth in terms of the number of booster vaccines administered across Europe.

He added that boosters will give people vital protection against the Omicron variant and pleaded for people to take the third dose as soon as they are notified by the HSE.

“People will be getting a text to be called forward. That will offer an appointment, but it will also offer the opportunity to book through their GP… and equally through pharmacies.

“This is a really important appointment that we should all set for ourselves, and we know people are coming forward in great numbers yesterday, but please don’t defer it… My encouragement for people is really come forward. Use the opportunity of the appointment when you get it, if not use some of the other channels,” he said.

Separately, chief medical officer Dr Tony Holohan has said that all of the evidence seems to suggest that the Omicron Covid-19 variant will spread more quickly than Delta.

Dr Holohan said the early evidence is now “very clearly” pointing towards an increase in transmissibility.

“The early evidence is very clearly now pointing towards an increase in transmissibility, that seems increasingly certain. The question of severity is still not known, we’re seeing a reported increase in the number of hospitalisations reported with those early cases in South Africa,” he told Byran Dobson on RTÉ’s News At One.

“It’s too early to conclude but the important thing to get across is that even if it’s less severe, if it’s more transmissible and can generate more cases that in itself at a population level can still paradoxically create a significant challenge.

“All of the evidence seems to be that Omicron will spread more quickly than we’ve seen with Delta.”

Dr Holohan said it is important that people travelling home from the UK for Christmas take into account their vaccine status and what level of socialisation they intend to engage in.

“People will make different risk assessments depending on their individual circumstance, it’s important that people would be aware and understand what the pattern of this disease is and it is changing on an almost daily basis,” he said.

“It’s only two weeks since this disease was first named, we’ve only known about it for a short period of time. People need to take into account their vaccine status, whether they’re likely to be meeting up with other vulnerable people and what level of socialisation they intend to engage in.

“What we’re advising is that people also need to take account of travel involving areas where there is reported high levels of community transmission and unfortunately the UK is one of those regions right now and by the UK, I mean mainland Great Britain.”

Dr Holohan said the Covid-19 booster vaccine will be important in protecting against Omicron and he urged people to come forward and avail of the jab.

“What we do expect is if it has this transmission advantage that it seems to have, it will in the way Delta did over Alpha, become dominant and that’s just the natural expectation. So, we don’t have an ambition to prevent this from occurring because that simply isn’t going to be possible unfortunately.

“It’s really important to try and slow down its spread into and throughout the country. The more we can extend our booster programme to give protection the better. We have confidence that the booster will be important in protecting against Omicron in addition to all the public health measures.”