The UK government has developed a COVID-19 contact tracing app. Health Secretary Matt Hancock revealed that the National Health Service's digital innovation branch, NHSX, was working on an app that will help track the spread of COVID-19. The app is simply called NHS COVID-19 and it's designed to work alongside the UK's Test and Trace scheme that started on 28 May 2020.

"If you become unwell with the symptoms of coronavirus, you can securely tell this new NHSX app, and the app will then send an alert anonymously to other app users that you've been in significant contact with over the past few days, even before you had symptoms so that they know and can act accordingly," explained Hancock during a UK daily pandemic briefing on 12 April.

Here's everything you need to know about the NHSX contact tracing app, including when you can get it on your mobile device.

How will the NHSX contact tracing app work?

Once installed, the NHSX contact tracing app will use Bluetooth Low Energy (BLE) signals to keep track of handsets and relay that data. It will detect when you're in significant contact with other individuals running the app via Bluetooth, and using this method, build up a traceable contact map.

No names will be given and all information will be anonymised with every user having a randomised ID - although the first part of a user's postcode will need to be input into the app when you start using it. You won't share anything until you need to make a report, with all the data remaining on your phone until you need to report that you're having COVID-19 symptoms.

NHS

The mobile app will work by letting users self-report if they're experiencing symptoms of the virus, with all data heading into a centralised data server in the UK. From this server, notifications are then sent out to those IDs that you've been in contact with.

A notification might say: "If you're on public transport, go home by the most direct route. Stay at least 2m away from people if you can. Find a room where you can close the door [and] avoid touching people, surfaces and objects," although the actual details of what you'll receive are still to be confirmed.

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If a user tests positive for COVID-19 it will trigger an alert to others they were exposed who may need to quarantine. For those who need testing, the app will the provide a route into getting a test from the NHS.

The science behind transmission will guide the app's response, so as more is learnt about the conditions under which coronavirus is transmitted, the app will adapt so that it's more accurate in alerting those people who have some into contact with an infected person, says the NHS.

It may also be that, in the future, users of the app are asked if they will also share location data, so that the site of these contacts is then available to the NHS too. The aim here will be to highlight potential hotspots for spreading the virus - for example train stations - and action can be taken.

NHS

"It would be very useful, epidemiologically, if people were willing to offer us not just the anonymous proximity contacts but also the location of where those contacts took place - because that would allow us to know that certain places or certain sectors or whatever were a particular source of proximity contacts that subsequently became problematic," said CEO of NHSX Matthew Gould, according to TechCrunch, when the app was discussed at the Common's Science and Technology Committee on 28 April 2020.

Use of the app will go hand-in-hand with contact tracing carried out by humans, as well as the wider testing network that's now available in the UK.

Will the NHSX contact tracing app be safe to use?

Health Secretary Matt Hancock addressed privacy concerns over the NHSX contact tracing app at its original announcement, explaining it'll be completely voluntary to use. The NHSX also won't keep the data from the app any longer than necessary.

"All data will be handled according to the highest ethical and security standards, and would only be used for NHSX care and research," Hancock said. NHSX has also promised to publish its security and privacy whitepapers with the app's source code so experts can verify its security, while it has also been consulting with experts from NCSC to ensure privacy and security.

The NCSC has published more detailed information on how the app will work technically. 

Privacy was also discussed in detail at the Common's Science and Technology Committee on 28 April 2020. During this session it was outlined that there will be privacy assessments on a regular basis: "At every stage we will do a data protection impact assessment, at every stage we'll make sure the information commission knows what we're doing and is comfortable with what we're doing so we will proceed carefully and make sure what we do is compliant," said Gould. 

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The app has triggered concerns, however, around privacy, because will be asked to willingly share information about those contacts that the HNS will be able to access. This will create a social graph and even though users will be anonymised privacy advocates are concerned that this will become a from of state control, because it's a centralised system. There's also concern that hackers could access data that's stored on these centralised servers.

The use of anonymised IDs and the way the service works, will mean that an individual cannot identify another individual, unless they have very few contacts. If, for example, there's someone who never leaves the house and only has one contact detected by their phone - like a carer - then it become obvious that the carer was exposed to the infection.

Will the NHS app actually work?

One of the barriers that's faced by any app is what functions of a smartphone it can actually use. As soon as contract tracing apps were suggested, the conflict that might arise with Apple or Google's own privacy guidelines were raised. We talk a lot more about Apple and Google below, but let's look at one problem the NHS app might face. 

Apple keeps tight control over what can access Bluetooth in the background, not allowing third-party apps constant access to Bluetooth. As Bluetooth is the system that the NHS app relies on, not being able to have background access to BLE would mean that it wouldn't function as devised - it will only access that Bluetooth data when the app is open, which means it might only work in contact tracing in those conditions. 

Whether Apple has changed the rules for these apps is unknown. We've asked Apple for comment, but there has been pressure on Apple to support these types of apps, to make sure that these functions will actually work. The BBC's tech correspondent - Rory Cellen-Jones - has had access to the app, saying "Some technical experts have said the NHS app will not work properly on an iPhone unless it is kept open and running in the foreground. The team behind it insist that is not the case - although that is impossible for me to verify."

France finds itself in the same situation as the UK, wanting its own StopCovid app to work in the same way as the NHS. "It is the responsibility of companies like Apple to do everything possible to develop appropriate technical solutions so that national applications work," said Thierry Breton, European commissioner for internal markets, talking about a meeting with Apple CEO Tim Cook. 

How many people will need to use the NHS app to make it effective?

The NHSX thinks more than 60 per cent of the population needs to use the app for it to be effective in helping the country return to normality, but more recent reports have suggested that 80 per cent of smartphone users (56 per cent of the population) would have to use it for the best results, according to experts at the University of Oxford talking to the BBC.

The big data team at Oxford - advising the NHSX team - has not included the over-70s in that group, as it's assumed they will be shielding at home when lockdown restrictions start to lift, although there will be some benefits if the uptake is a little lower. In Singapore, where a similar system was tried, the uptake was only 12 per cent, although the launch of a similar system in Australia, called Covidsafe, saw over 2 million installs in a matter of days. 

The problem is getting high numbers of people to use any app, especially as it's going to be voluntary to use.

When will the NHSX contact tracing app be available?

The new NHSX contact tracing app is currently in development and testing and is not yet available to download and use on iPhones and Android devices. 

Currently the app is in testing on the Isle of Wight. Announced by Hancock at the Downing Street briefing on 4 May 2020, the Health Minister outlined that the Isle of Wight made a perfect testing ground for the system because it's isolated, has one authority and one NHS Trust, and fairly low levels of coronavirus currently. This doesn't make any difference to lockdown measures at this time on the Isle of Wight.

The app has been approved on both the Apple AppStore and Android's Google Play, so as soon as wider roll-out is started across the UK, users will be able to download and install the app. The UK Government initially said they were looking at the middle of May for a launch, but that date has now come and gone - and the latest information suggests the app will launch in the middle of June.

It has been outlined by NHSX's Matthew Gould that the app is likely to launch without the full feature set, with future functions added as the app evolves, but that the important thing is that the app launches alongside the outlined programme to ease lockdown measures - test, track and trace.

What part do Google and Apple have to play?

Google and Apple announced on 10 April that they were jointly working on an API (application programming interface) that would allow Android and iPhone devices to anonymously share the data needed to carry out contact tracing, using Bluetooth Low Energy. As Apple and Google jointly control pretty much the entire smartphone market, this would cover virtually all smartphones in use, except some much older models, of which there are few in the UK.

Initially, this will provide a platform that healthcare agencies can use to get the data from devices to share with other users. In the future, the system would allow Google and Apple devices to handle the data at a system level, decentralising that data and ensuring that privacy was protected by the terms of Apple and Google respectively. That means you won't have to have the app open and running all the time - it will work in the background and would also mean that the data remained private.

Following discussion that NHSX and Google-Apple were at odds about how this should work, reported in The Guardian, it has been confirmed that the NHS won't be using the Apple and Google system. This will mean that the NHS has access to the data, so outbreaks can potentially be tracked nationally, if users are happy to share location data.

However Matt Hancock, in response to questions from the BBC on 5 May, confirmed that the NHS continues to work with Apple and Google and it emerged on 8 May that NHSX had commissioned a second app using the Apple-Google system, according to The Financial Times. This, potentially, would enable the NHS to use either system based on testing.

What is a centralised and what's a decentralised system?

A lot of the talk around contact tracing apps talk about centralised and decentralised systems. In a centralised system, all the data heads into a central server for processing. This is the system that the UK's NHS is planning to use; it's also being used by France, Australia, Norway. 

The advantage of a centralised system is that the NHS can use the data to get more information about how the virus is spreading, locations where there's a lot more contacts reported which might points to a outbreak hotspot that needs some other form of intervention. 

A decentralised system only shares data between phones, meaning that it's a lot more private and secure, because that data can't be accessed by anyone else, like a government body. 

What about the EU's rules?

The EU has outlined how it believes that contact tracing apps should work for EU member states - and that's going to include scrutiny of Apple and Google's system, to ensure that it dovetails with the EU's own privacy rulings. Those things include that an individual shouldn't be able to be identified through the system and that it is disabled once the need for contact tracing has passed.

The EU has essentially mandated that either a centralised system (as will be used by the NHS) or a decentralised system (using the Apple and Google system) will be accepted, as long as it's only used for coronavirus contact tracing, anonymised and voluntary.