The Chief Medical Officer warned the Health Minister that level 3 was not working, and that the level 5 was inevitable.
Dr Tony Holohan highlighted NPHETs concern over hospital capacity and how transmission levels are already overwhelming the testing and contact tracing systems.
He warned that in the few days since NPHET last met and subsequently recommended a move to level 5, things had only deteriorated.
The letter warned that level 3 was simply not working and more aggressive measures were needed as soon as possible to avoid case numbers hitting 2,500 per day by Halloween.
In what could be read as an effort to save Christmas, an argument was made to go to level 5 for six weeks rather than 3.
The CMO explained that a reproduction number of 0.5 for three weeks would would get daily case numbers down to around 300. But once level 5 measures were eased, numbers would rapidly grow to 1000 a day by mid-December.
Six weeks of the r number at 0.5 would get case numbers down to around 100, with cases climbing to 300 by early January once measures are lifted.
