Yesterday’s announcement about Step 3 of the government's Covid roadmap was accompanied by three modelling papers from Imperial College, Warwick University and LSHTM that give us insights into what the Covid-19 endgame will look like. They also hint at some options for saving thousands of lives at negligible cost. Here we look at four key take-aways from the studies.
1. The expected size of a third wave has been substantially reduced
The headline news out of the latest modelling from Imperial and Warwick is that the expected number of deaths and hospitalisations has been halved from what they expected just six weeks ago. Imperial’s central case suggests 9,000 deaths in England over the coming year and Warwick’s 7,000, compared to 16,000 and 19,000 respectively at Easter. Across the UK as a whole, that means the central expectation if now for around 10,000 further deaths, compared to 20,000 previously.
Two main changes in the assumptions appear to be driving this. One is a new assumption about reduced infectiousness of vaccinated people, based on the recent PHE study – which showed that vaccinated people who subsequently get infected are 45 per cent less likely to pass on the virus. This has a big impact on the level of population protection in terms of transmission.
The second is that the Imperial modelling implies a sharp change in the mix of vaccines used, in light of the new guidance that under-40s should receive an mRNA vaccine where possible. Raising the proportion of Pfizer and Moderna vaccines to around 45 per cent of the vaccinated population, compared to an assumed 20 per cent six weeks ago, further increases protection levels on their assumptions.
One negative development is that both Imperial and Warwick appear to have revised up their estimate of the R number ‘excluding immunity’ from 3 to 3.5 once all restrictions are removed. That assumption shift alone would add several thousand to the anticipated death toll, but the bad news here is outweighed by the good news on infectiousness.
2. The number of deaths is very sensitive to vaccine rollout speed
The new central case numbers are very encouraging, but they are highly dependent on the interaction between the pace of easing restriction and rollout of the vaccines. As we pointed out in our recent report, to avoid a third wave the government needed to either accelerate rollout or consider delaying the final easing step. While movements in the other assumptions have reduced the size of the problem, this remains true.
Warwick’s analysis suggests that if the pace of vaccine rollout were increased by 20 per cent - from the current rate of around 460,000 jabs per day across the UK to 550,000 per day – this would roughly halve the number of deaths to under 4,000 (in England). Meanwhile if the pace of rollout slowed by 20 per cent deaths could double to over 14,000.
3. Varying the rollout by geography could save thousands of lives
It may not be possible to increase the national rate of vaccine rollout, but with a bit of creativity we could save thousands of lives without changing the roadmap. Over the past 14 months some areas of the country – like London, where Imperial estimates an attack rate of 38 per cent - have been hit harder by Covid-19 than others. But this means that protection from past infection in the capital is high compared to some other regions, and it will reach herd immunity at a lower level of vaccine coverage than other regions. In short it is unlikely that there will be any resurgence in the virus in the capital.
At the same time, any third wave will be highly concentrated on the regions that have seen fewer infections to date. Warwick sees the North East and Yorkshire as vastly more exposed than any other region.
With six weeks to go until the final easing step, it’s time to consider taking a regional – or even more local – approach to vaccine rollout. Accelerating the programme in more exposed areas could allow us effectively to achieve the Warwick ‘rapid rollout’ scenario without increasing jab capacity nationally. Targeting accelerated rollout on even finer levels of geography could also save lives – particularly in places that are seeing accelerating case numbers like Bolton.
4. VOCs are dangerous – but we won’t need a lockdown to handle them
Both Imperial and Warwick study the likely impact of a ‘variant of concern’ – specifically the South African one in the case of Imperial – becoming established in the UK. The numbers are scary. Lifting all restrictions in the face of the B.1.351 variant, they estimate, could lead to 124,000 deaths in England alone. Under various assumptions the picture could be worse still.
But all is not lost – far from it. The modelling results illustrate that in the face of such a variant only relatively minor controls on social mixing should be enough to completely avoid any such surge in deaths. Unlike at the start of this year we are no longer in the position of needing full lockdowns to save lived
Imperial estimates that deaths under their central VOC scenario would drop to just 2,700 if Step 3 restrictions were maintained. In other words, they expect that we can almost entirely eliminate any third wave without having to close pubs or shops again. With the efficacy of some vaccines thought to be higher against the South African variant than others, it would not take long before booster jabs would enable population protection against the VOC to be enhanced such that even these residual restrictions could be lifted.
Clearly there remains a lot of uncertainty about the impact of different VOCs on vaccine efficacy. And of course a new and scarier VOC could emerge at any time. But for now at least the message from the latest SAGE analysis is very positive.