How does the new NHS Covid-19 App Work?

The new Covid-19 App is currently being trialled out on the Isle of Wight, with the government planning to roll it out nationwide by the end of the month. But how exactly does it work?

The app relies on contact tracing which involves a person who is infected recounting their movements and activities to build up a picture of who else may have been exposed. It will use Bluetooth signals to determine movements and paint a picture.

The Bluetooth technology within phones has to be switched on at all times and will broadcast an identifier that is unique to that device. The identifier is a random string of numbers that regularly updates and includes no personal information. When a user’s phone is near another Bluetooth device the two will exchange identifiers. A list of all devices in the form of their unique codes are stored on your phone for 28 days. Nothing else will happen unless a user indicates they are experiencing coronavirus symptoms.

Within the app there is one central question: “how are you feeling today?” If the user responds that they are feeling unwell, they tap on the prompt and are asked a series of questions including whether they have a high temperature and a persistent cough (both are defined within the app). The user is also asked to state when the symptoms first started.

If a user has both symptoms then the information can be sent to the NHS. Users will then see a link telling them to follow health advice such as self isolating and potential details for testing. When the user informs the app that they have symptoms, the NHS’s technology will determine whether the people they were in contact with would need to be notified. This is done using a risk algorithm and not everyone is notified immediately.

Both the government and the NHS have been keen to point out that the app does not gather information that could identify an individual. No location or personal information is gathered, this information will only be required if a person reports having symptoms.

However, users will be asked to enter the first half of their postcode when they first download the app, so that the NHS can track the spread of coronavirus. The app will also collect information regarding the type of phone the user uses alongside information around Bluetooth usage. This includes the unique IDs of the devices the phone has interacted with and how long the devices were communicating and how strong the signal between devices was. A stronger signal should arguably mean you were closer to an infected person.

Officials hope that these pieces of data can be combined into a coronavirus modelling system to help understand more about how the virus spreads.

Whilst it is not compulsory to download the app, both the NHS and the government recommend that people do so, believing that the more people that download it the more effective it will be. Furthermore, members of the University of Oxford believe that at least 60% of people need to download the app and to use it for it have any sort of impact.

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