The countries making up the UK, the island of Ireland and the Channel Islands have all upgraded their respective Covid-19 contract-tracing apps, enhancing them to improve accuracy, capability and interoperability.
Across England and Wales, the NHS contact-tracing app developed by the UK arm of Swiss software firm Zühlke Engineering and officially launched on 24 September, and which has now been downloaded 19 million times by about 40% of eligible smartphone owners, has undergone its first in-field upgrade to increase the app’s accuracy in identifying close contacts and remove unnecessary exposure notifications to improve communications for app users.
The NHS app is now said to be able to estimate better the distance between users to increase the accuracy of close contact notifications that it sends out. The NHS says the app’s accuracy will be even better than at launch. Working in collaboration with scientists from the Alan Turing Institute to utilise the latest version of the Google/Apple API at the heart of its decentralised nature, it claims that it is the only app globally to have innovated its underlying technology to exploit this latest API update.
This is said to improve the estimation of distance via Bluetooth, further helping to break chains of transmission. This means it can better assess whether someone is at risk of having caught the virus, and therefore needs to isolate.
The app uses a combination of distance, proximity and infectiousness of a contact to calculate the risk threshold at which someone is notified to self-isolate. The latest update uses technology to better measure distance, which means the NHS can reduce the number of low-risk contacts notified to self-isolate without impacting the number of high-risk contacts notified to self-isolate.
This, said the NHS, means that those who are notified by the app to self-isolate are at high risk and should isolate to break the chain of transmission and control the spread of the virus. The NHS also noted that the risk threshold is not static – it can be turned up or down and will be kept under review and changed periodically to reflect the stage of the pandemic. The update will also lower the threshold set to notify users at risk of having caught the virus to self-isolate.
The update also addresses the issue of “ghost” exposure notifications, which were reported following the September launch. The updates were sent by Google and Apple when the app interacted with the API, improving the clarity of app communications. By removing these unnecessary “ghost” exposure notifications, the NHS says it will be clearer to app users that they only need to self-isolate when instructed to do so by the app. The new update will be available immediately on all eligible Android phones, and iPhones running on operating system iOS 3.7 or above.
The NHS has issued a guarantee that the updates in the app have been designed with user privacy in mind, so it tracks the virus, not people, and uses the latest in data security technology to protect privacy. The system generates a random ID for an individual’s device, which can be exchanged between devices via Bluetooth (not GPS). These unique random IDs regenerate frequently to add an extra layer of security and preserve anonymity.
The app does not hold personal information such as names, addresses or dates of birth, and only requires the first half of a postcode to manage local outbreaks. No personal data is shared with the government, police or the NHS.
Commenting on the upgrades, NHS Test and Trace director of product Gaby Appleton said: “The team behind the app are continually working to improve its accuracy and user experience, to make it as simple as possible to keep people safe. 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.”
The England and Wales app is also set to become interoperable with contact-tracing apps in Scotland, Northern Ireland, Jersey and Gibraltar. When interoperability is implemented, if an app user tests positive for Covid-19, they can choose to upload the anonymous keys their phone has been exchanging with other phones, so that alerts can be sent to other app users in the UK, Jersey and Gibraltar.
The apps in Scotland, Northern Ireland, Jersey and Gibraltar, as well as that in the Republic of Ireland, use underlying source code developed by Irish software developer NearForm and open sourced by the Irish government to the Linux Foundation Public Health under the Covid Green project.
“Covid-19 doesn’t recognise borders and we are seeing more countries and states collaborate in this effort to provide an additional layer of protection for people travelling between jurisdictions,” said NearForm CEO Cian Ó Maidín, on the linking of apps between Scotland, Northern Ireland and Jersey. “The app puts the power into people’s hands to protect themselves and others while helping to slow the spread of Covid-19.”
The Irish app is one of three national apps in the initial launch of the European interoperability gateway. This is designed to ensure that EU contact-tracing apps will work seamlessly across borders and so users will only need to install one app and will still be able to report a positive infection test or receive an alert, even if they travel to another EU member state.
