The chairman of the Irish Epidemiological Modelling Advisory Group has released the modelling data used by Government and the National Public Health Emergency Team (Nphet) in the decision process of delaying the further reopening of the country.
Professor Philip Nolan said although it has been a "difficult and disappointing week for many," he described the impact the Delta variant could have on the country as "stark" and that "caution is well-advised."
Prof Nolan shared the group's data which is based on "scenario models to help Nphet and Government think quantitatively about risks and likely disease trajectories and impacts".
It has been a difficult and disappointing week for many, as the rise to dominance of the delta variant has delayed plans for wider reopening; but the likely impact of delta is stark, and caution is well advised. 1/36 pic.twitter.com/ThDA2zhAfb— Professor Philip Nolan (@PhilipNolan_SFI) June 30, 2021
Using comparisons to the rate of the virus last summer, Prof Nolan says "because the level of infection in late June 2020 was very low, it was weeks before the underlying exponential growth became apparent; essentially the seeds of the October 2020 surge were sown in July and August 2020".
Prof Nolan said the group used this as their starting assumption the level of social mixing with summer reopening could either be moderate or high, giving us an R of 1.4 to 1.6.
He added that the Delta variant, which was not present last summer, is far more transmissible.
According to the European Centre of Disease Prevention and Control, the Delta variant is 97% more transmissible than the strains circulating last summer.
Prof Nolan highlighted that a rise in cases will "inevitably lead to hospitalisation and mortality, though the rates will be far less than we experienced without vaccination; nonetheless, a long wave of disease leads to a significant number of adverse outcomes".
The model also shows that 99% of the potential deaths that would occur would be in those over 40.
"While 70 to 80% of cases will be in people under 40, there will be a lot of infections and a lot of adverse outcomes in people over 40; about 70% of the hospitalisations and over 99% of the deaths would be in people over 40," Prof Nolan said.
Commenting on vaccine effectiveness, he said while they offer "extraordinary protection", they are not perfect.
"We have almost 500,000 people aged 70 and over; even if the vaccine is 95% effective in preventing severe disease, 25,000 people remain vulnerable," he said.
Summarising the 36 tweet thread on Twitter, Prof Nolan said the data collected "illustrates one thing: A variant with a transmission advantage can do very significant damage if we let it spread in a partially vaccinated population, the scale of the damage depends on the transmission advantage, and it starts slowly and escalates rapidly."