Figure 1.

Flowchart of participants according to inclusion and exclusion criteria for this study.

Entire cohort is given first, before subdivision into vaccinated and unvaccinated CA. Note here the two age groups had differing time periods for data consideration (adolescents aged 16–17 years: able to receive vaccination after August 4, 2021; children aged 12-15 years: able to receive vaccination after September 18, 2021). Further subdivision provides numbers of individuals for periods of Delta and Omicron variant predominance in UK. Considered time frames for Delta and Omicron variant predominance were not contiguous; thus, numbers of CA within each time frame do not sum to numbers across the entire study period.

Not valid result = test result proxy-reported as “failed test” or “still waiting”.

Irregular logging = proxy-reporting with intervals of more than 7 days between proxy-reports during illness.

PCR – polymerase chain reaction. LFAT – lateral flow antigen test.