More than 31,000 close contacts were identified during the first week of the test and trace system in England, figures show.
Of those, 85% were reached and asked to self-isolate for 14 days.
This was from 8,000 people testing positive for coronavirus - two-thirds of whom provided details of who they had been close to.
Around 25,000 contact tracers were recruited in England and started work at the end of May.
The NHS figures, which cover 28 May to 3 June, are the first to be released showing the progress of England's contact tracing scheme