Extended Data Fig. 3: Uncorrected (raw positivity rates) and corrected (debiased) Pillar 1+2 PCR-positive prevalence estimates against (gold-standard) REACT estimates from randomised surveillance for REACT rounds 10 and 11.

Each point corresponds to an LTLA. Each scatter plot compares Pillar 1+2 prevalence estimates against unbiased estimates from the REACT study. Panels (a,c) show REACT round 10 data (11th Mar - 30th Mar 2021), and panels (b,d) show round 11 (15th Apr - 3rd May 2021). Uncorrected results are shown in panels (a-b) and bias-corrected cross-sectional estimates in (c-d). Horizontal grey lines are 95% exact binomial confidence intervals from the REACT data. Vertical black lines in panels (a-b) are 95% exact binomial confidence intervals from the raw, non-debiased Pillar 1+2 data. Vertical black lines in panels (c-d) are 95% posterior credible intervals from the debiased Pillar 1+2 data. Neither set of prevalence estimates has been corrected for false positives/negatives. Note that in panels (c-d), the CI widths are systematically tighter for the debiased Pillar 1+2 compared to the REACT data, pointing to the useful information content in debiased Pillar 1+2 data. The number of independent tests underlying each mean and (horizontal) CI for the REACT data varied between 289 and 1,894. The number of independent tests underlying each mean and (vertical) CI for the Pillar 1+2 data varied between 977 and 29,998.