Table 1.

The operational considerations at time of investigation

Indicator	Release frequency	Reporting/completeness lag
Google Trends	Daily	1 days
NHS 111 Pathways	Daily	2 days
LFD Tests	Weekly	1 days
NHS COVID-19 app	Weekly	2–3 days
ZOE app	Ad hoc	1 day estimated

Note: A 1-day reporting/completeness lag corresponds to yesterdays’ collected data being available today. More frequent releases allow for more flexibility in times of increased demand for analysis, particularly in a fast-changing epidemic. The reporting/completeness lag ‘eats into’ lead times, reducing how useful a leading indicator is in practice.