Fig. 4

Percentage of study population recorded as a confirmed case, stratified by intervention tier status. For each panel, we display the number of cases by date and by intervention tier status, from 12th October 2020 to 17th December 2020. The half term week for most of England is shown by the dark grey shaded region, with the period corresponding to the national lockdown shown by the light grey shaded region. The faded dots indicate the tier status prior to the national lockdown that was introduced on Thursday 5th November 2020. a Pupils in primary schools. b Pupils in secondary schools. c Teachers in primary schools. d Teachers in secondary schools. It should be noted that several regions changed tiers when lockdown was lifted on 2nd December, leading to an observed discontinuity in the data displayed in the figure on this date