In NPHET's advice to the Government to bring in Level Five restrictions across the country, Chief Medical Officer Tony Holohan warned that otherwise there will be up to 2,300 Covid-19 cases by November 7.
He also warned that there will be up to 43 people being admitted to the hospital every day by that date.
Dr Holohan made the warning in an October 4 letter to the Health Minister Stephen Donnelly. The Government chose to disregard the advice and put the whole country in Level Three.
In that letter, he also pointed out that there had been 22 confirmed cases in critical care on the morning he wrote it.
And he stated that 243 out of the available 281 critical care beds in the country were occupied.
Dr Holohan, who returned recently from compassionate leave to care for his wife, also warned that “the measures currently in place are not sufficiently controlling the disease”.
He said this was evidenced by a high volume of community transmission and “sustained increases”.
He warned: “Disease modelling shows that if current trends continue, 1600 to 2300 cases will be notified per day by November 7.
“The modelling also shows 43 people with Covid-19 being admitted to hospital per day by that date "In light of the above, NPHET believes proactive and robust measures must now be taken so that very significant suppression of the disease with the reproductive number well below one is achieved.
"It is therefore recommended the government apply Level 5 measures across the country from midnight Monday, October 5, for a period of four weeks.”
Dr Holohan’s letter was published on the gov.ie website around the time Taoiseach Micheal Martin announced Level Three restrictions would be introduced.
The letter also said there should be - in effect - an emergency mobilisation of State resources to protect the most vulnerable in society.
There must be "immediate activation by all state agencies and other bodies of all necessary processes, plans, supports and measures to ensure the necessary services are available to those who need them over the coming four weeks”, he said.
This should, he said, include physical and mental health and social care services.
He said: “It is vital we do everything in our power now (underlined) to arrest the current trajectory nationally and very substantially suppress the virus back down to a low level of transmission in advance of the winter months".
He also recommended that Level Five measures be accompanied by “comprehensive and consistent communications”.
Dr Holohan said: “These communications should provide clarity on the measures in place, on why those measures are in place and on what each individual, organization, and employer can do to suppress the virus.”