NPHET's modelling of the direction Covid could take over the coming months didn't take into account changes to the vaccine roll-out.
It means the models cabinet used to make a decision on delaying re-opening of indoor dining were out of date.
The models predicting hundreds of thousands of cases of the new Delta variant were a big part of the reason Cabinet Ministers decided to delay re-opening.
Taoiseach Micheál Martin told Ministers on Tuesday they included the changes to the vaccine roll-out that will allow younger people to access AstraZeneca and Johnson & Johnson.
However, CMO Dr Tony Holohan told opposition TDs yesterday, the modeling did not take into account a faster vaccine roll-out.
Which means the models cabinet used to make decisions were already out of date, and likely more pessimistic than they should have been.
The re-opening delay was savaged by some at the Fianna Fáil and Fine Gael parliamentary party meetings last night.
TD Marc MacSharry said he has no confidence in the Taoiseach, and even less in party colleague and health Minister Stephen Donnelly.
While a number of TDs across both parties said if legislation is needed to ensure only vaccinated people will be allowed to dine indoors, they'll vote against it.