The HSE's chief clinical officer has cast doubt over the zero-Covid approach, questioning whether it can be "realistically sustained".
Dr Colm Henry said that Ireland has learned "to its cost" that suppressing and sustaining low levels of the virus is "extremely difficult".
The zero-Covid strategy has been backed by opposition parties, who have called for the Government to take a more aggressive approach to driving down Covid-19 levels.
However, Taoiseach Micheál Martin has questioned how it can be applied in Ireland for a long period of time.
Dr Henry said that Ireland has a five-day average of 1,200 cases per day, which is half of what it was last week, but he warned the numbers are still far too high.
"We all aspire to a zero-Covid and what we're trying to do now, and more successfully than we thought we would only a couple of weeks ago, is a suppression from the huge levels of infection that we were seeing," he told RTÉ's Morning Ireland.
"The question with the zero-Covid is, not so much the shared aspiration to get this down to the lowest possible level, it's how that can be realistically sustained.
"If you just look at our figures, beginning (of) December, we were the second best in Europe, in terms of 14-day incidence.
"Within a very short timeframe, (we had) the second worst. The virus doesn't give you credit for good behaviour or good results.
"It doesn't have any memory for that and in a very short time period, when our country was released from Level five to Level three for a short period of time, there's increased socialisation and contacts and so on, we saw a catastrophic fall in performance."
Dr Henry said that hospitals across Ireland are seeing a high volume of sick people, which he described as "completely unprecedented".
He said the number of people in hospital today is 10 times higher than what it was in early December.
"It's an enormous increase in cases," he added.
It comes as testing of close contacts of confirmed Covid-19 cases resumes on Friday.
At the end of December, testing of close contacts was suspended temporarily to prioritise testing of symptomatic cases.
It was a result of pressure on the testing system due to widespread community transmission seen in the third wave.