An update to the coronavirus app for England and Wales is being rolled out that will improve accuracy and stop alarming ‘ghost’ notifications.
The technology uses Bluetooth on smartphones to keep an anonymous log of other app users that an individual comes into contact with, informing them if they have been near someone who tests positive for the virus.
Since launching on September 24, the app has been downloaded 19 million times by around 40% of eligible smartphone owners, according to the Department for Health and Social Care (DHSC).
The latest set of improvements will better estimate distance between people to increase the accuracy of close contact notifications sent out by the app.
Using a combination of distance, proximity and infectiousness of a contact to calculate the risk threshold, the update should reduce the number of low risk contacts notified to self-isolate, without impacting the number of high-risk contacts being informed.
A “possible Covid-19 exposure” notification on the app that caused panic will also no longer appear.
The message read: “Possible Covid-19 exposure. Someone you were near reported having Covid-19. Exposure date, duration and signal strength have been saved.”
At the time, DHSC said these particular alerts were default privacy notifications from Apple and Google – who created the underlying technology – to alert people that the app is sharing information with the system.
Confusion persisted despite a follow-up message being introduced on October 13 to reassure users.
“The team behind the app are continually working to improve its accuracy and user experience, to make it as simple as possible to keep users and their loved ones safe,” said Gaby Appleton, NHS Test and Trace director of product.
“We are thrilled that over 19 million people have chosen to download the app to help protect their loved ones while preserving their privacy, and that over 680,000 QR codes have been created by businesses to support digital contact tracing.
“This update builds on that success by increasing accuracy, and also removing ‘ghost’ exposure notifications, meaning users will only be notified if they need to self-isolate.
“The more people who use the app, the better it works, so I encourage all those who have not yet downloaded the app to do so.”
Work is also underway to enable the system to communicate with contact tracing apps from Scotland, Northern Ireland, Jersey and Gibraltar.
Once it is implemented, a person who tests positive will be able to alert users that they have been near to beyond just England and Wales.
This ability is expected to arrive in early November after consultations with the National Cyber Security Centre are completed to ensure it is secure and reliable.
“It is thanks to the hard work of the NHS Covid-19 app development team and colleagues at the Turing Institute that we have been able to exploit the updated API technology in this way,” said Mark Briers of The Alan Turing Institute.
“This update increases the accuracy, meaning those most at risk will be notified to self-isolate.”