A spokesperson for the World Health Organisation (WHO) says a lockdown should not be used as a country's only strategy.
Dr Margaret Harris was speaking as the Government considered implementing level five coronavirus restrictions for six weeks on the back of NPHET advice.
She told Newstalk Breakfast with Susan Keogh: "Our position is not that you can't do lockdowns, it's simply that don't use a massive lockdown as your only strategy."
"Ultimately, you use a lockdown - it's essentially putting the entire society into quarantine.
"You do that at the point where your services are getting overwhelmed, where you simply can't do the other things you need to do - the contact tracing, the testing, the caring for people, you've run out of beds - so at that point you put a freeze on things.
"They do work, the problem is of course the economic and social consequences can be very high.
"But this time around - it sounds like bad news, but it's good news - people are better prepared and do understand what's going on far better."
On talk of a potential vaccine by the new year, Dr Harris said the WHO is examining a number of factors.
"There have been eight to nine vaccines put into what we call phase three trials, and at this stage those trials will be starting to get the data to suggest whether or not they're seeing effectiveness.
"So I think what we're hearing from a number of trials is they're quite happy with their effectiveness.
"But we at the WHO look at a number of things: first of all, we want to see that it's protecting at least 50% of the people who are vaccinated.
"Second of all, we really want to know, be very confident, of the safety: because this is going to be rolled out to the whole world to all levels of people.
"And the third thing is to understand who are you going to give it to first - you must prioritise the highest-risk groups first.
"They are the people who in some ways they may be the people who could spread it, but also they're the people most at-risk of dying from it".
She added that they have set up a vaccine distribution system called the Covax Facility, which all EU member states have signed up to.
"We've actually invested in nine of the most promising and looking at scaling them up at the same time as the studies are going on".
"180 countries have signed up to that - including the European Union countries - to ensure again that the highest-risk people get it first all around the world.
"As you know, until everyone's safe no one's safe".