The Chief Medical Officer has not ruled out further restrictions for Ireland ahead of the expected "wave" of Omicron cases in the coming weeks.
Dr Tony Holohan said public health officials would continue to closely monitor the situation with Covid-19 over Christmas and would give further advice to government if they felt further rules were warranted.
It comes as a range of new measures came into effect at midnight which include changes to closing times for hospitality venues, close contacts and weddings.
The restrictions, announced by Taoiseach Micheal Martin on Friday, have been implemented in response to the threat posed by the Omicron variant.
The strain is now dominant in Ireland, with 52% of cases now due to the Omicron infection.
Dr Holohan said that NPHET did not have plans in place to recommend additional rules or a lockdown before New Year's Eve.
However, nothing can be ruled out as the situation with the virus is changing rapidly.
Asked whether more restrictions will be introduced before Christmas, the CMO said: "We're not necessarily planning on that basis, there are a series of measures that are only coming into effect today.
"Christmas Eve is Friday, Christmas Day is Saturday so it's really important that people hear the message that it's now down to you as an individual for what you can do to cut your own social contacts, staying away if you've got symptoms and following all the basic public health advice to protect you and your loved ones."
Speaking on RTE's Morning Ireland, Dr Holohan also denied that NPHET would be meeting with the Taoiseach after Christmas to announce a lockdown.
"I know there was a report in a newspaper yesterday to say there was a firm plan for us to meet on December 30 to announce a lockdown at that point and we have already indicated as such to him, that's simply untrue," he said.
"The Taoiseach himself over the course of the weekend, although I didn't directly hear him in the media, did make clear that nothing is ever ruled in, we continue to monitor the effect, but a series of measures have now been mandated by government.
"They're only coming into effect today, we believe they will substantially cut the total volume of social contact across society and we as individuals can now take measures to cut our own individual social contact, to stay away if you have symptoms and to follow all the basic public health advice.
"We think all those measures combined will have a chance to take pressure off hospitals and to maintain as much as we can the essential public services."
Dr Holohan said he would not speculate about at what point more rules would be recommended.
Rather the trajectory of the disease will continue to be monitored, with advice from the ECDC and other worldwide health bodies also taken into account.
"This is a virus that got a name just over three weeks ago, you're asking me in part about a period of time that's at least three weeks away, a lot has changed in the last three weeks," he said.
"We monitor on a day by day basis so if we think a change is mandated, we will give advice in relation to that."
The top public health doctor also expressed his concern about the Omicron variant as he urged people to adopt personal responsibility when it comes to their activities over the festive season.
He said Ireland is "potentially at risk from a major surge of the virus" that is now being felt in countries across Europe including Norway, Denmark, the Netherlands and the UK.
"The measures that have been taken are intended to substantially cut the quantum of social contact across society," he said.
"Government has now made these decisions and mandated them and you as an individual can start to take measures to cut your own social contact.
"Over the course of the coming days, think about the things you absolutely have to do, the things you may not need to do.
"It's a difficult message at this time of year, I completely understand at Christmas time."
The virus has a "substantial growth advantage", he warned, and had a "really rapid spread ability".
Dr Holohan said he did also not want to speculate about what next Christmas could be like, saying his focus is on this week.
"We're right now in the situation where, and I don't like using analogies like tidal waves, but the wave of infection that this is going to present is right in front of us," he stated.
"The measures we take right now are what are going to protect us and that's what we collectively need to keep our focus on."
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