A record number of people were told to self-isolate in England and Wales last week after getting pinged by the NHS app.
The latest figures released by the NHS show 689,313 people in England and Wales were pinged by the app at told to self-isolate in the week ending 21 July.
It is the highest weekly figure since the app launched, with the number of pings rising sharply through July.
Under the current system, anyone who is identified through the app as having been in "close contact" with an infected person is instructed to self-isolate at home for ten days.
It is not a legal requirement however, to either use the app, or to self-isolate if requested to via it.
A computer algorithm is used to determine the "risk" posed to people who have spent more than 15 minutes within two metres of someone who has tested positive, including in the two days before they first showed symptoms.
The rise comes after ministers announced a list of key sectors from which workers could be eligible to avoid self-isolation, including those working in medicine, food production and defence, provided they have received both jabs and have a negative test.
But the plans have been criticised for being overly complicated after it was revealed the rules would only apply to some workers, with businesses told to provide the details of individual staff who they wished to be given the exemption.
Health secretary Sajid Javid has already confirmed the self-isolation rules in England will change from 16 August when all fuly vaccined people allowed to avoid the ten day quarantine if pinged by the app, provided they receive a negative test result.