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 in 24 hours 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 their close contacts.
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 the contact tracing scheme.
‘More to do’
Baroness Dido Harding, who runs NHS Test and Trace in England, said there was still “more to do to improve the speed” of the system but she said “the vast majority of people are participating and playing their part”.
“I want to say thank you to people for protecting themselves and their communities,” she added.
The system has been unable to reach 15% of close contacts, either because they were unavailable, their contact details were wrong or they did not respond to texts, emails or calls from contact tracers.
They are told to try calling 10 times in a 24-hour period.
Some who were reached did not agree to self-isolate.
But Baroness Harding said there had been “good numbers of compliance”.
As lockdown eases, and people start to return to work and go out to shops, it’s expected the number of contacts people have will start to grow from a low starting point.
Does this represent a good start?
The data from the test and trace system in England has been eagerly anticipated – after all, this system will be crucial in helping contain local outbreaks, enabling the country to ease out of lockdown.
It is still early days, but how should we interpret these findings?
Firstly, the system seems to be pretty good at reaching the contacts of people who have tested positive, if those positive cases engage with the contact tracers and provide details in the first place.
The problem is a third of people who test positive are not providing details.
This could be because the contact tracers are not as good as they should be at tracking those who do not engage with the online forms (the first point of call for the system).
There have been suggestions that sufficient translation support is not always available, for example.
But incorrect contact details being provided and people simply refusing to take calls – despite repeated attempts – are certainly factors too.
The key to the success of the system will be both an efficient service and public engagement in taking calls and following the advice to self-isolate.
What is test and trace?
It’s a way of controlling the spread of the virus by asking people who have tested positive for coronavirus to share information on who they have been in close contact with.
It starts with getting a test if you have symptoms.
If you test positive for the virus, tracers will text, email or call you and ask you to log on to the NHS Test and Trace website to provide details of contacts.
Close contacts will then be contacted and told to stay at home for 14 days, even if they don’t have symptoms.
This process is organised slightly differently around the UK.
What happens around the UK?
In Scotland, the system is called NHS Test and Protect. Between 28 May and 7 June 2020, 741 contacts were traced from 681 positive tests for the virus – an average of 1.5 contacts per case.
Northern Ireland was the first part of the UK to bring in contact tracing.
Contact tracing started in Wales on 1 June and is called ‘test, trace, protect’.
Have you been contacted by a tracer? Tell us by emailing.
Please include your telephone number if you are willing to speak to a BBC journalist. You can also contact us in the following ways: