The UK's NHS is stepping back from the development of its homegrown solution and instead turning to the system proposed by an Apple and Google partnership to power its coronavirus contact tracing app. The change was announced and confirmed by the Department of Health and Social Care (DHSC) on 18 June.

The move is a major change of direction for the app. Development and discussion around the app had seemingly stalled in recent weeks, leading many to suspect that it wasn't working the way that NHSX - the technology group responsible for the project - had hoped. 

The shift will see in-built contact tracing from Apple's iPhone and Google's Android devices providing the information about close proximity contacts, allowing a network of contacts to be alerted should a user test positive for the virus. However, the DHSC has confirmed that the app will integrate the learnings from its trials on the Isle of Wight.

"...we have agreed to share our own innovative work on estimating distance between app users with Google and Apple, work that we hope will benefit others, while using their solution to address some of the specific technical challenges identified through our rigorous testing," says a joint statement from Baroness Dido Harding, executive chair of NHS Test and Trace, and Matthew Gould, CEO of NHSX.

It's expected that the NHS app will look the same as the version currently in testing on the Isle of Wight, but the underlying mechanics of the application will now be substantially different.

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The Google-Apple system works on a "decentralised" model, meaning that the data remains on the phone and anonymously notifies other users when triggered by a positive COVID-19 diagnosis. This information is not available to the NHS, meaning that authorities cannot gather the data and analyse it.

Originally, that had been on the UK's wishlist, allowing the identification of hotspots so that action could be taken and to allow wider epidemiological data gathering, in a so-called "centralised" system. Privacy advocates had raised warning flags about this approach, preferring the decentralised model proposed by the tech giants.

When Apple and Google first proposed their own system of contact tracing, Health Secretary Matt Hancock had said that there was potential to use the system; indeed, it was reported in by the Financial Times in May 2020 that NHSX was commissioning a second app so that the UK could use either system moving forward. 

On the announcement that the NHS was switching to the Google-Apple system, Hancock said: "Countries across the globe have faced challenges in developing an app which gets all of these elements right, but through ongoing international collaboration we hope to learn, improve and find a solution which will strengthen our global response to this virus."

From the outset, technology experts had warned that any contact tracing system that didn't use the Google-Apple approach would struggle to be effective, because of the way that Apple handles access to Bluetooth when apps are running in the background. Bluetooth is the essential element of the system and although the original NHSX app claimed to have found a way around the problem, we suspect that this is still part of the issue. 

Using core code from Google and Apple should mean that any app based on their system should be more efficient in terms of battery life, as well as having the necessary access to the device's hardware. At the same time, the DHSC is saying that it is sharing its own findings based around contact proximity with the aim of improving the system that Apple and Google offers.

Although this is a change of direction, there's still no timeline for the app's release.