The UK's contact tracing COVID-19 app has been updated to fix a bug that meant the system failed to send notifications to users who should have self-isolated.

The software update will also mean that the NHS contact tracing app will stop sending false alarms, and "phantom alerts" which were reported last month, suggesting exposure to the virus and then disappearing.  

Users whose “risk score” should have triggered an alert, due to possible exposure among their contacts, were not alerted to self-isolate due to the error, according to an article in The Sunday Times [paywall].

As a result, “shockingly low” numbers of users had been sent warnings since the app was released, according to a government source.

WHY IT MATTERS

As millions more people in England moved to tier two this weekend, and with impending lockdown restrictions set to take place from Thursday, the contact tracing app will aim to keep more people safe amid the pandemic.

The update will mean that more people will be asked to self-isolate by the app after being in contact with someone who has tested positive.

THE LARGER CONTEXT

The contact tracing app for England and Wales has recently hired the third boss in six months - Gaby Appleton, a former director at Elsevier. She will take over from Simon Thompson, the former Apple executive who was appointed to run the programme in June. 

In September, it was reported that the app was unable to log a third of England's positive tests after the issue was revealed by a user on Twitter.

Last week, it was also reported that a function in the app that allows those to claim government financial support wasn't added to the app.

The French government has experienced stability issues with its contact tracing app, and recently rebranded it TousAntiCovid as it announced plans to place 38 regions under curfew restrictions.

ON THE RECORD

The app’s head of product Randeep Sidhu and Gaby Appleton, director of product for Test and Trace, said in a Department for Health and Social Care blog post: "The update to the risk threshold is expected to increase the number of people asked to self-isolate by the app, having been in close contact with someone who has tested positive."

“We believe lowering the threshold is necessary to reduce the R (reinfection) rate and break the chain of transmission.”