Public health chiefs warned the Government of in excess of 2,000 deaths by the autumn in its most “pessimistic” model of the trajectory of the Delta variant.
A letter from chief medical officer Dr Tony Holohan to Health Minister Stephen Donnelly warned that a “significant fourth wave of infection” is likely, due to the Delta variant “rapidly” becoming the dominant strain in Ireland.
On Tuesday, the Cabinet agreed to delay the return of indoor hospitality after the advice.
It set out four scenarios outlining the impact the Delta variant could have on case numbers, hospital admissions and deaths.
The most optimistic scenario projects 165 deaths between July 1 and September 30, while the most pessimistic predicts 2,170 deaths in that timeframe.
The other two scenarios modelled, central one and central two, project between 545 and 1,230 deaths in that time.
The Taoiseach said the National Public Health Emergency Team (Nphet) had advised him the situation is likely to “land somewhere between” those two scenarios.
He added: “What is clear from Nphet’s advice is that if we were to proceed as we had planned in our entirety from July 5 onwards, we would significantly increase the risk of the more negative scenarios and the pessimistic scenarios that they have outlined.
“That really would have a very significant impact on people, on our health service and on mortality, and that was the context in which Government took that advice.”
Tánaiste Leo Varadkar compared the projections under the optimistic model as akin to levels to be expected during flu season.
However, he said given the stark projections of the pessimistic models, the Government had decided to proceed with caution.
He told a press conference on Tuesday: “If you take the optimistic one, we’re talking about maybe 165 deaths over the next three months.
“Roughly one or two a day, each a tragedy, each a relative, each a family grieving.
“But similar or not as bad as what you’d expect to see in the average flu season, and certainly not a reason to shut down a country.”
He added: “On the other hand, the pessimistic scenario is totally different, over 2,000 deaths occurring over a three month period.
“A wave as severe as any that we’ve experienced to date, with hospitals coming under enormous pressure and ICU’s in particular.
“So with that in mind, bearing in mind that the pessimistic scenario is a potential outcome, we decided that we’re going to be cautious and we’re going to err on the side of caution.”
The letter also warned that a high level of transmission could have “significant impacts on the reopening of schools and the tertiary education sector in Autumn.”