The NHS contact tracing app will stop sending “false alarms” telling people they have been near someone who has tested positive for coronavirus, bringing an end to one of the biggest issues for the software in England and Wales.
Government officials have confirmed that Google and Apple, which make the technology underlying the app, would update their software to stop the “ghost” messages, which have been causing widespread confusion and anxiety among the 19 million people who have downloaded the app.
The update also means more people will be asked to self-isolate by the contact tracing app after they have been in contact with someone who has tested positive – a move officials claimed would “keep more people safe”.
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The change comes as a result of a refinement of the app’s algorithm, made possible by Google and Apple’s update.
Officials responsible for the app, which operates in England and Wales, said the change – which they believed would make the app more accurate – was necessary to reduce the spread of the virus.
In a blog post on the government website, Gaby Appleton, director of product for Test and Trace, and Randeep Sidhu, head of product for the NHS COVID-19 app, said: “We believe lowering the threshold is necessary to reduce the R rate and break the chain of transmission.”
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Yet low-paid workers asked to self-isolate by the app still cannot claim the government’s £500 support payment, even if they are entitled to it, as Sky News revealed last week. Officials confirmed they were looking at solutions.
The news of the change to the app’s algorithm comes at a moment when the government is under increasing pressure to introduce a national lockdown, after similar measures were brought in France and Germany.
When it was first introduced ministers said the app would replace blanket lockdowns with targeted ones, although as yet there is little evidence that the app is playing a significant role in reducing transmission.
The change to the algorithm has been made because an update to Google and Apple’s system makes it possible for NHSX, the NHS innovation unit behind the app, to use more accurate data on the proximity of devices.
Previously, Google and Apple’s system put data into one of three “buckets”: low, medium and high.
Now it supplies more granular data, meaning scientists at the Turing Institute can make the app more accurate, allowing them to distinguish between low, medium and high-risk situations.
Officials used this information to lower the “risk threshold”, the level at which the app’s algorithm determines that a user needs to self-isolate.
With cases rising around the country, this meant that the app would ask more people to self-isolate — but fewer people would be told to do so unnecessarily.
“Compared to when we first launched the pilot of the app in August, this update reduces the chance of telling you to isolate when you’re at low risk, without reducing the number of people at high risk who are notified to self-isolate,” said Ms Appleton and Mr Sidhu.
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The news that the app will no longer send “exposure notification” messages will be welcomed by many users, who have complained to Sky News about the alerts.
Unlike apps in other countries, the app in England and Wales used a custom algorithm developed by scientists at the Turing Institute. This triggered a feature in Google and Apple’s system which sent “exposure notifications” warning people they had been near someone with coronavirus.
Although they were meant to be ignored, these “false alarms” caused a considerable degree of confusion and anxiety, with Sky News finding at least one person who had wrongly gone into self-isolation after receiving one.
“By removing these notifications, users can have the confidence that if they have a contact notification, they know it is from the app itself,” said Ms Appleton and Mr Sidhu in their blogpost.
The app for England and Wales is also set to work alongside contact tracing apps in Scotland, Northern Ireland, Jersey and Gibraltar. Officials said an update meaning data could be shared between the apps was expected to be released in early November.