The country is at risk of being struck by a new strain of Covid-19 amid fears it could drive a Christmas surge in infection.
Labs around the country were placed on alert for the new strain yesterday after it emerged it was behind a rise in cases in southeast England, home to many Irish emigrants who may be travelling here for Christmas.
A senior Government source said increasing travel restrictions for passengers travelling from Britain was not being considered at this stage, but the situation was "being monitored very closely".
Deputy chief medical officer Dr Ronan Glynn said news of the new strain - which does not appear to be more virulent - was relayed through a rapid alert system yesterday.
He said it was "too early" to say if it is in this country, but he could not give any "false confidence" at this point that it will not impact the effectiveness of Covid-19 vaccines.
Prof Kingston Mills, of the School of Biochemistry and Immunology in Trinity College, said he has no data on the reported new strain yet but if it transpires to be correct it will become the dominant strain here.
"If it spreads more readily, that is bad news as it is easier for people to contract it," he warned.
UK authorities believe the new strain, which is being examined at their top laboratory facility at Porton Down, is not more deadly and there is a low risk it will not respond to vaccines.
Chief medical officer Dr Tony Holohan repeated that all non-essential travel into and out of the country should be postponed, including to and from Britain.
It comes as two more deaths were reported here yesterday and 264 new cases, a drop from 429 on Sunday.
Dr Holohan said, however, there are often lower case numbers early in the week and the five-day average has risen to 312 per 100,000.
The 14-day incidence of the disease here is also falling at a slower rate.
He again appealed to people to "minimise the amount of interactions" they have with other people and select the things that can be done and choose those as essential.
It is crucial to plan ahead to minimise risk of picking up the infection if anyone is meeting with older people or those with an underlying illness.
There were 215 patients with Covid-19 in hospital yesterday, a rise from recent days, and 33 patients were in intensive care, an increase of two since the weekend.
Yesterday's new cases included 79 in Dublin, 24 in Donegal, 19 in Kerry, 18 in Limerick, 14 in Kildare and 14 in Wexford. The remaining 96 cases are spread across 16 other counties.
Meanwhile, Lorraine Nolan, head of Ireland's medicines watchdog the Health Products Regulatory Authority (HPRA), said the European Medicines Agency's scientific committee will meet on December 29 to decide if the Pfizer-BioNTech vaccine should be recommended for approval.
It will then go to the European Commission. It will hold another meeting on January 12 to see if the Moderna vaccine should be recommended.
Ms Nolan said the vaccines are being given "thorough scientific examination" and there will be no "lowering of the bar" in granting them approval.
She said members of the public have questions about the speed at which the vaccines were developed, but she reassured them the process was accelerated but not rushed.
Various factors contributed to the pace of the vaccines' development including large funding, the technologies involved and the genetic sequencing of the virus which happened early allowing for work to get under way.
"It will be the most intensively reviewed medicine because all the regulatory bodies are doing it at the same time around the globe," she added.
Regulatory bodies have been receiving ongoing results from vaccine trials for many months and have not had to wait until all the final data was complete.
She said she is worried about false information on vaccines filtering through social media and urged people to get their information from reliable sources.
The two potential vaccines under review aim to prevent people who get the virus from getting ill, but more studies are needed to see if they can prevent transmission of the virus from one person to another.
The HPRA will be involved in monitoring the performance and safety of the vaccine once it is rolled out here, she added.
An article in Anaesthesia - the journal of the Association of Anaesthetists - says that in order for the global vaccination programme to be successful, the available vaccines must be able to do all three tasks: prevent infection becoming established in an individual, prevent disease progression, and prevent onward transmission.