Modelling the Return of Freedoms
Bulletin 122 | Matt Fletcher, Adele Groyer and John Roberts
On 14 June, a large batch of papers was published by SAGE. These set out further modelling of the impact of easing restrictions in England – in particular, moving to Step 4 of the roadmap. These were part of the decision-making process by the UK Government which resulted in delaying Step 4 from 21 June to 19 July.
Each of the modelling papers sets out many scenarios, using different assumptions for things like:
Transmission advantage of Delta against Alpha
Behavioural impact in response to Step 4
The papers are emblematic of the uncertainty around the current position. Depending on the assumptions made, the models produce radically different projections of cases, hospitalisations, and deaths. Whilst it is clear that we are already at the start of a third wave of infections, there is uncertainty around the extent to which vaccination and prior infection will mitigate the impact on hospitalisations and deaths.
In this bulletin, we summarise the number of deaths that are projected under some of the key scenarios set out in the papers. We identify similarities and differences between the modelling approaches and consider what new evidence might be gathered in the coming weeks to determine which path the UK might be on.
The numbers of deaths and hospitalisations projected are especially sensitive to assumptions about vaccine efficacy against severe outcomes, and immune escape. Data is still emerging to support these assumptions for the Delta variant.
We consider the more extreme adverse scenarios unlikely given the latest evidence on the
effectiveness of two doses of the vaccine against hospitalisation and death, even for the Delta variant.