Levelling Up Vaccinations

Covid-19 Covid-19

Levelling Up Vaccinations

Posted on: 21st May 2021
By Multiple Authors
Ian Mulheirn
Executive Director for UK Policy and Chief Economist
David Britto

On Wednesday Deputy Chief Medical Officer Jonathan Van Tam framed the challenge as a ‘straight race between the transmissibility of this new variant and vaccine delivery’. And a lot of lives depend on winning that race. Bolton, Bradford and Blackburn are on the watch list – canaries in the coalmine as we try to figure out whether the new ‘Indian variant’ of Covid-19 is significantly more transmissible than the Kent one.

The government’s epidemiological advisors think there’s a ‘realistic possibility’ that the variant is 50% more transmissible. Earlier this week, JVT himself suggested that a 20-30% increase is more likely. But rather than waiting to find out, we should be taking a more proactive approach, and using the vaccine doses we have to maximise protection through regional variation in the rollout.

In the short run the risk is that a more transmissible variant rips through the country before vaccine protection is fully rolled out, resulting in potentially thousands of deaths that could have been avoided – despite high vaccine uptake (don’t forget that in any third wave it’s still vaccinated people who are likely to be most at risk of dying). While surge vaccinations of vulnerable people are being targeted on hotspots, this isn’t the right strategy to contain the spread.  For that we also need the surge to get vaccine coverage up among the people most likely to spread the disease.

Outside the hotspots, there are two obvious – and relatively blunt - options to mitigate the risk of a wider surge in infections. One is to accelerate vaccine rollout and the other is to delay easing restrictions for a number of weeks – and potentially reverse it in some area.

Analysis by the Warwick University modelling team for SAGE shows just how important it is to maximise protection levels before opening up fully. Their analysis suggests that the number of deaths from an exit wave could double if rollout was 20% slower than planned, or halve if it was 20% faster. The good news is that rollout is currently about 13% up on the SAGE assumptions. But the bad news is that a more transmissible strain of the virus could more than undermine that progress. It may be necessary to delay the final step of the roadmap until the school summer holidays to buy ourselves time to raise vaccine coverage.

But there’s another tool in the armoury that hasn’t been considered: tilting the pace of vaccine rollout towards the most exposed parts of the country. Not just to hotspots and not just to the vulnerable, this would be a wholesale acceleration of rollout across the less-protected half of the country to allow safe easing of restrictions as quickly as possible.

Click on the buttons above to view past infection and vaccination rates across Local Authorities. All figures are for 17 May

Communities’ protection against Covid depends on the degree of population immunity conferred either through past infection or vaccination. Our analysis shows that levels of protection vary substantially across the country, as the map illustrates. Some areas, like Bromley and Bexley in London, were hit hard by earlier waves, resulting in high rates of past infection. But they’ve also had pretty solid vaccine uptake. If you combine the rate of past infection with vaccine-induced protection (using SAGE assumptions on efficacy), Bexley has population protection of around 67%.

But other areas are far more exposed. Take Cambridge for example, where it seems likely that just 15% of the population have been infected in the past (versus around 26% for England as a whole), meanwhile only 49% of the population has had a first dose of vaccine (54% nationally). As a result, it is among the more exposed areas of the country with overall protection of around 50%. A similar story can be told about other places like York (55% protection) and Islington (51%) - where despite a fair degree of past infection, low vaccine take-up so far leaves both areas more exposed than the national average.

Levelling up protection would mean slowing the rollout in those areas with already high rates of protection and shifting doses to the more vulnerable areas.

How would that help? One reason is fairness: a vaccinated person in a low-protection area is simply more vulnerable to a third wave than an equivalent person in a high-protection area. Boosting protection in the lagging areas therefore reduces the postcode lottery.

But more importantly it could also significantly reduce the total number of infections over the coming weeks as vaccine immunity builds. This happens because as the level of protection in an area converges on the herd immunity threshold, the marginal benefit of each extra percentage point of protection diminishes. So more cases can be prevented and lives saved by equalising protection.

Note: Herd Immunity Threshold lines exclude seasonality effects. Click on the date buttons above to view protection levels across Local Authorities over time

The interactive chart above shows our estimated protection levels for all of England’s local authorities, lined up from the least to the best protected. The horizontal lines indicate the likely herd immunity thresholds (HIT) prevailing after step 3 (17 May) and step 4 (currently planned for 21 June), for both the Kent and Indian variants. These are taken from the Imperial College SAGE modelling assumptions and the Indian variant is assumed to be 25% more transmissible.

The chart illustrates how by the planned time of step 4 only a handful of areas are likely to be clear of the Kent variant HIT (assuming vaccine rollout continues on current patterns). However by 26 July half of all local authorities are over the line. But whenever step 4 is taken, the number of additional cases will be minimised if the protection levels can be brought up in the lagging areas.

If the Indian variant was to become established, as seems likely, the HIT would rise still further, perhaps to 77% (on Imperial assumptions with 25% higher transmissibility). Even by the start of September, when vaccine rollout is complete, protection levels in England are only likely to reach to around 71%. But here too, levelling up protection would minimise the scale of any surge. Meanwhile, extending vaccination to adolescents, as we proposed in our earlier report, could be sufficient to get average protection levels into the safe zone.

There may be other things to factor in to a decision about how to redistribute protection – perhaps focusing more on areas of deprivation, for example. But whatever the formula, it’s clear that taking a local area approach and levelling up vaccine rollout could hold the key to saving lives and ending the covid nightmare.

Note on our modelling: To estimate Covid protection levels across Local Tier Authorities in England, we use vaccination data from NHS England (latest release, 20th May 2021) to calculate local vaccination coverage to date, and positive Covid test data from the UK Government coronavirus dashboard to calculate past infection rates. To estimate unrecorded infections, we use Imperial College’s cumulative Covid case estimates, detailed in their paper Evaluating the Roadmap out of Lockdown: Step 3, submitted to SAGE on 5th May 2021. For each of the seven NHS England regions, we calculate a scale factor to map recorded positive tests from the dashboard to Imperial College’s estimates of cumulative cases, and apply these regional scale factors to each Local Authority in that NHS region to calculate present infection levels. We also project vaccinations forward based on Imperial’s approach, matching Imperial’s estimated take-up rates across age groups, weighted by the local age distribution in each Local Authority to reflect potential variation in vaccine hesitancy across regions. We assume 2.7 million doses are available for use in England each week, and divide doses between Local Authorities proportionately based on the outstanding age demographic profile in each area waiting for vaccination. We model second doses as delivered 11 weeks after first doses, and replicate Imperial’s vaccine efficacy rates, assuming a 55:45 split between Pfizer and AstraZeneca (overall vaccine infection efficacy rates: 80% after first dose, and 85% after second dose). Importantly, we do not project Covid infection rates past 17th May 2021, meaning that estimated protection increases from mid-May onwards are the result of vaccinations only

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