Figure 3.

(A) Comparison of an exponential model fit to round 18 (blue), and to round 17 and round 18 (red), and a P-spline model fit to all rounds of REACT-1 (black, shown here only for rounds 16, 17 and 18). Shaded blue and red regions show the 95% posterior credible interval for the exponential models, and the shaded grey region shows 50% (dark grey) and 95% (light grey) posterior credible interval for the P-spline model. Results are presented for each day (X axis) of sampling for round 16, round 17 and round 18 and the weighted prevalence of swab-positivity is shown (Y axis) on a log scale. Weighted observations (black dots) and 95% confidence intervals (vertical lines) are also shown. Weighted prevalence of swab-positivity by age group (B) and region (D) for round 17 and round 18. Bars show the prevalence point estimates (grey for round 17 and orange for round 18), and the vertical lines represent the 95% confidence intervals. (C) P-spline models fit to SARS-CoV-2 swab-positivity data from all rounds of REACT-1 for those aged 17 years and under (red), those aged 18–54 years inclusive (blue) and those aged 55 years and over (green). Shaded regions show 50% (dark shade) and 95% (light shade) posterior credible interval for the P-spline models. (E) Neighbourhood smoothed average SARS-CoV-2 swab-positivity prevalence by lower-tier local authority area for round 18. Neighbourhood prevalence calculated from nearest neighbours (the median number of neighbours within 30 km in the study). Average neighbourhood prevalence displayed for individual lower-tier local authorities for the whole of England. Regions: NE = North East, NW = North West, YH = Yorkshire and The Humber, EM = East Midlands, WM = West Midlands, EE = East of England, L = London, SE = South East, SW = South West.