Four Lessons From the UK’s COVID Delta Wave
- By Bilal Hafeez and Ben Ford
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- 3 min read
The UK’s decision to lift all restrictions during a surge in COVID cases has drawn much criticism. But we find the scale of testing overstates the current wave’s size. Also, the young not old are getting infected, reducing the impact on hospitalisations. And the 17 May partial re-opening (indoor dining) impacted people’s movements more than the 19 July full re-opening. We therefore expect no repeat of the second wave where hospitalisations reached 40,000 and daily deaths 1,000.
1. More Testing, More Cases
All eyes are on the UK’s surging number of new COVID cases. The current seven-day average is just under 40,000, but it reached as high as 47,000 last week. That is near the peak of 60,000 in January during the height of the second wave.
Yet both hospitalisations and deaths are running much lower. During the January peak, the seven-day average of daily deaths reached over 1,200 a day – today it is around 60. That could partly be due to vaccinations and the age demographics of those infected (see below), but also partly to false comparisons to the peak of the second wave. Indeed, a big reason for more cases today is more COVID testing.
At the peak of the second wave, England was conducting around 450,000 tests a day – mainly PCR tests. Today, the number is more than double at over 1,000,000 – this time with most being lateral flow tests (Chart 1). The test type could be impacting the link between cases and deaths. Most studies have found lateral flow tests are less accurate than PCE tests.
That aside, we can rescale the second wave to estimate the case numbers were there as many tests conducted then as today. We find during the January peak, daily cases would have reached over 140,000. Given the current rate of 40,000, this suggests comparisons to January may be misplaced. Indeed, the rescaled second wave sees 40,000 cases reached in October 2020. Back then, average daily deaths was around 50 – much closer to the 60 we are seeing today.
This implies that despite case numbers today being close to the January peak, adjusting for the scale of testing, the comparison should be to earlier stages of the second wave.
2. Age Matters for Hospitalisations
A major concern with a rise in cases is that it could lead to a big increase in hospitalisations (and deaths). This in turn could force the reinstatement of lockdown measures to ease the burden on the healthcare system. At the height of the UK’s second wave, almost 40,000 patients were hospitalised with COVID. Today, there are only 5,000 such patients. As mentioned, rescaled, the correct parallel would be October 2020, when hospitalization numbers were similar to today. The question, then, is will we eventually see a progression like in the second wave to much higher hospitalisations?
We think it unlikely as the underlying dynamics appear different. Most notably, infections among older demographics are currently much lower than the second wave peak unlike younger demographics. Indeed, the biggest increases in recent COVID cases have been among teenagers and twentysomethings (Chart 3). More teenagers are testing positive now than the height of the second wave in January. Older age groups have seen much smaller increases in cases (Chart 4). It may even be hard to classify a third wave among them.
Importantly, the elderly have a much higher probability of requiring hospital treatment when catching COVID. During the second wave, hospitalisation rates for the elderly reached 53 per 100,000, while for younger demographics they reached 6 per 100,000 (Chart 5). This means that cases among the elderly end up correlating much more strongly with overall hospitalisations (Charts 6). But the high two-dose vaccination rate among the elderly appears to have dramatically reduced the hospitalisation rates for this demographic (Charts 5 and 6). Indeed, while hospitalisation rates of younger demographics are at second-wave peaks, the elderly hospitalisation rate is much lower than its earlier peak.
3. The UK Effectively Re-Opened in May
While much fanfare (and criticism) accompanied the 19 July full re-opening (the so-called ‘Freedom Day’), data suggests the 17 May lifting of restrictions was more meaningful. It was then that indoor dining was allowed. Reservations for seated dining surged soon after and have since subsided despite Freedom Day (Chart 8). Moreover, credit card spending on social activities, people visiting retail and recreational sites, and car traffic were already picking up before restrictions lifted, and they peaked around or soon after the 17 May partial re-opening.
Perhaps the summer is seeing less activity from people, which may have been the government’s intention, but little evidence exists so far that Freedom Day has dramatically shifted behaviour.
4. The Self-Isolation Pattern Is Similar to Wave Two
One restriction still in place is self-isolation. In the UK, people who have come into contact with an infected person must self-isolate for a period. Track and Trace teams identify the close contacts. The most recent data for the week up to 7 July show over 380,000 people identified as such, with 90% reached and told to isolate. Since Track and Trace began, over 9.5 million people have been identified as close contacts.
For context, at the height of the second wave, in one week of January, over 730,000 close contacts were identified. And a clear relationship exists between case numbers and the number of contacts identified (Chart 12). Currently, the ratio of contacts to infected people is around two, similar to the second wave. Therefore, the surge in close contacts is not unusual in the UK context.
