The idea of transforming Ireland into a 'Zero-Covid' island is based on an "utterly false promise" that carries huge risks, Professor Philip Nolan said last night.
Prof Nolan, of the National Public Health Emergency Team (Nphet), was speaking as the proposal to eliminate the country of Covid-19 to allow the nation to return to normal is gaining ground among some Opposition politicians.
"I think it is an utterly false promise to say we can put certain things in place and go back to Level 0 or 1 in weeks or months," he insisted.
He said no system could guarantee the exclusion of a new disease or variant and Ireland would remain a "leaky country" vulnerable to both threats.
The aim now is to drive down community transmission of the virus here as much as possible, which will allow for "strategic options" to be taken as Covid-19 vaccines are rolled out further.
Chief medical officer Dr Tony Holohan also said this country has essential links with Europe, including Northern Ireland, which makes it unrealistic to seal our borders.
He shared the aspiration to get the virus down as far as possible and said many of the measures in place are taking us in the same direction while trying to slow the spread of more infectious forms of the virus.
"We simply could not seal the borders and stop movement of people in and out," he said.
But if the country opened up as normal there was the risk of new variants taking root here and rapidly intensifying, he added.
Earlier Prof Nolan said the spread of the virus is declining rapidly with 1,466 new cases yesterday.
"Incidence is falling and by working collectively to reduce contacts we have achieved suppression of transmission with the R number estimated at 0.4 to 0.7.
"We are maintaining an extraordinary effort but still we have a long way to go.
"We must maintain full suppression for several weeks if we are to achieve strategic options for the future.
"If we keep this up, we would be down to 200-400 cases per day by the end of February."
However, another 47 Covid-19 deaths were reported yesterday.
Dr Holohan said while incidence is falling it remains high.
He said: "We are continuing to experience high mortality with 878 deaths so far in January.
"I am concerned about the high incidence we are seeing in long-term care settings and vulnerable groups.
"Our efforts to stay home and break transmission of the disease will save lives. Please continue to follow the public health advice and support each other to keep going."
The numbers of patients with Covid-19 in hospital fell to 1,567 but the number in intensive care remains high, although stabilised, at 216.
The forecast is that daily case numbers could reduce to 200 to 400 a day at the end of February. At that point, there would be around 600-800 Covid-19 patients in hospital with 60 to 80 in intensive care.
There is concern about what will happen when the country opens up a significant level of activity and fears that vaccinations will trigger a relaxation in anti-Covid rules and this could lead to a sharp rise in infection.
The more infectious UK variant continues to gain dominance here and nine cases of the South African strain had been found which were travel-related. No case of the Brazilian strain has been found.
HSE chief Paul Reid announced yesterday that close contacts of confirmed cases are to be offered tests again from today.
Dr Lorraine Doherty of the Health Protection Surveillance Centre provided examples showing how one event can spark a chain of transmission.
In one case, a person who picked up the virus in a meat plant set off a trail of transmission leading to 220 being infected.
A separate outbreak among third-level students gave rise to 61 linked cases. One student worked as a waitress at a wedding, infecting 16 other staff and guests.