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COVID-19 cases with S gene target failure, England, 15 November–31 December 2021 (n = 937,155)
COVID-19: coronavirus disease; PPV: positive predictive value; SGTF: S-gene target failure; SGTS: S gene target surveillance.
Panel A: points represent daily values, the line represents PPV of the past 7 days. Panel B: data are shown on a log scale. Public health action phases are described in detail in the Table.
