Table 2 Scenarios for improvements

From: The epidemiological impact of the NHS COVID-19 app

 

Per cent reduction in total case burden in phase 2 (in addition to reductions observed for the current implementation of the app)

Analysis

Modelling

Statistical extrapolation

Increase uptake to 35.9%—current 90th percentile—for all LTLAs (improve equity)

11% (5–15%)

21.0% (14.5–26.8%)

Increase uptake across the board by 20 percentage points (mass improvement)

24% (10–34%)

41.5% (29.5–51.5%)

Switch to opt-out notification (5% drop-off)a

6.6% (2.5–11%)

Not applicable with this method

Improve adherence to quarantine by 20 percentage points

6.8% (5–8.7%)

Not applicable with this method

Reduce time to test result by one dayb

3.6% (0.6–6.7%)

Not applicable with this method

  1. Results are the per cent reduction in total case burden that would have occurred during phase 2. This is the further reduction relative to the cases that actually occurred, not relative to cases inferred in the absence of the app. Ranges shown are 95% confidence intervals for regressions, 2.5–97.5% sensitivity intervals for modelling.
  2. aCurrently, the app requires consent after the receipt of a positive test for contact tracing to be initiated, which is provided by 72% of users. We assume that changing to opt-out consent, for example, by consent at registration, would increase this to 95%.
  3. bReducing test turnaround time has many benefits not modelled here; we consider only faster digital tracing.
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