Without tracking identity or location, it measures time and distance between users, notifying them if they've come in close contact with someone who has later tested positive for the coronavirus.
Of the 8,237 identified by Test and Trace, a total of 3,297 have not been contacted - with 2,253 in the Black Country and 1,044 in Staffordshire. If a user reports in the app that they tested positive for covid-19, it will send an alert to other users who were in close contact over the last 14 days. After its proprietary system delivered poor results, the NHS backtracked on that decision and opted to work with the Apple and Google framework.
UK Health Secretary Matt Hancock has insisted the country's new coronavirus tracing app will be effective despite fears the vast majority of the population won't download it.
The app was originally meant to be launched at the end May - but a number of issues forced it to be delayed.
The app will be available to users running iOS 13.5 or later and Android 6.0 or later, and is free to download and use. "And it will help to keep us safe", Hancock went on.
People can also use the app to check in to venues on their smartphone by scanning QR-codes displayed at restaurants, pubs, bars and other businesses.
"We have worked extensively with tech companies, global partners, and privacy and medical experts - and learned from the trials - to develop an app that is secure, simple to use and will help keep our country safe", UK Health Secretary Matt Hancock said.
"That's a trade-off decision that a company like Apple can sensibly make, there are good commercial and good engineering reasons for making those decisions but that ultimately prevented the first app from functioning reliably".
"But if you need the support the financial support to self-isolate, then you can click through and declare that".
In England, only 64 per cent of non-complex contacts have been reached by the Test and Trace service, in the week up to September 9. However the government's logic appears to be that more features will encourage more people to download the app and thereby increase uptake and utility.
The app does not hold personal information such as your name, address or date of birth, and only requires the first half of your postcode to ensure local outbreaks can be managed.
"My main concern is not the app itself but the interaction with the testing schedule", she said. The whole idea is to catch contacts before they develop symptoms in that seven-day window when they won't be isolating.