Did putting areas into a higher tier have an impact on Covid-19 levels?

The answer is a resounding… yes! The LCP Covid-19 Tracker shows consistently that areas that were put into higher tiers subsequently saw substantially lower growth rates.

Using data underlying the Tracker, we’ve categorised England’s local authorities into seven groups, based entirely on the tiers they were in across December. Applying actuarial methods to estimate current cases over time in the different areas has produced much clearer results than we anticipated. (A full description of our methods can be found here).

Note that the chart is indexed, which gives a common starting point and allows us to compare the data more easily. The lines therefore represent rate of growth in infections, not the total number of Covid-19 cases.

Covid-19 growth was off the scale for areas that had been in Tier 1 – Herefordshire, Cornwall and the Isle of Wight, represented by the yellow line – increasing almost 20-fold before the January lockdown.

Areas that remained in Tier 2 after Boxing Day (the orange line) showed a 150% increase in Covid-19 cases over the next ten days, while cases in areas that joined Tier 3 on Boxing Day (light pink) only increased by 50%.

Tier 2 to Tier 4 transitions are represented by the two blue lines. For the six days after 20 December, areas represented by the lighter line were still under Tier 2 (along with “Christmas bubbles”), while the darker line had been in Tier 4 since 20 December. On cue, the lines diverged on Christmas Day. Once both groups had gone to Tier 4, the lines became parallel again – but the damage for the “Christmas bubble” areas had already been done.

The dark pink and black lines represent areas that were in Tier 3 at the beginning of December. In black line areas, the case rate was still growing early in December and the government put them into Tier 4. As a result, case growth in these areas started to subside on 20 December. In contrast, areas represented by the dark pink line did better before Christmas and so remained in Tier 3, but paid for this towards the end of the month, overtaking the black line areas.

Where might this lead?

As we progress through lockdown, there are some encouraging signs that cases are falling – and this will surely be a precursor for lower rates of hospitalisation and deaths. Unlike in the lower tiers, Tier 4 cases were fairly flat across the New Year, and now we are in a lockdown which is stronger still.

In addition, an increasing minority will have some immunity – either from the vaccine, with more than 4 million first doses in the UK given at the time of writing, or because they previously had Covid-19 (recent research from Public Health England finding an 83% lower risk of getting Covid-19 in individuals who have previously acquired it). Of course, the enemy has better weapons too – we are dealing with a more contagious variant.

The LCP Covid-19 Tracker is designed to estimate current infections and analyse recent trends rather than predict the future. However at time of writing, the Tracker estimates that cases have fallen by around one third over the last 12 days. This is before any material impacts of the vaccination programme have come through where the increasing immunity levels as the programme continues will lead to a hastening decline, especially in the most vulnerable groups. The potential impacts of the vaccination programme are outlined in detail in the Actuaries Response Group’s paper.

How can we use this information?

There are some learnings from the LCP Covid-19 Tracker that have wider applicability for governments, healthcare systems and individuals.

Think ahead

On 7 January the LCP Covid-19 Tracker was showing two days of decreases in cases for the first time since the December surge. But if one had just followed the PHE “date reported” figures, a similar two-day trend would not have been apparent until 10 January – even then one could have argued that the fall was just due to the slightly lower reporting which normally occurs around weekends. If you’re a decision-maker, that’s a valuable three days.

No estimates are perfect, but we developed the LCP Covid-19 Tracker to reflect the situation at local levels to help inform decision makers about daily rates in their area, current prevalence and testing times in order to provide appropriate advice to their population.

Take early and decisive action

As we’ve seen recently with exponential growth in some areas, any delay in acting makes the size of the challenge twice as hard. Governments need to consider when to impose – and loosen – restrictions especially in the knowledge of hospital capacity and how this could impact non-Covid-19 care too.

Monitor the experience

Sometimes events demand you change course. However, by catching the developments early, appropriate steps can be taken. That means being willing to be challenged – but not defeated – when reality turns out differently to expectations. We are continuously reviewing the LCP Covid-19 Tracker, not only to add new features, but also to ask ourselves whether the latest trends shown by the Tracker pass the ‘common sense’ test.

For those working in healthcare settings – especially at the moment – data-driven decisions based on the latest information can be the difference between life and death.