NHS Covid-19 app: Why does coronavirus contact-tracing tool keep giving me two notifications at same time?

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The NHS Covid-19 app is continuing to confuse users who are being sent a flurry of notifications.

The app now sends two notifications each time a potential exposure is found, even if it is then checked and found to be not significant enough to require action.

That double notification actually began as a fix for another design problem that left users wondering whether they were at risk. While it has fixed that problem, it has introduced a whole new one.

The initial problems arrived when users kept receiving a message that they had been subject to a “possible Covid-19 exposure”. The message gave very little extra information, and was usually not followed up with any useful guidance.

That was because the message is actually a technical reminder rather than anything to do with the app. It only indicates that the app has pulled information from the phone’s bank of possible exposures, with a view to analysing it to understand what the risk might be.

Developers then added another warning to fix that problem, which was widely reported as a bug but might better be described as a confusing part of the design. It’s that explanation that is the second message that shows to users – often only momentarily after the first one.

The two messages appear to show because they actually come from different parts of the process, and seemingly two different parts of the app. While there appears to be no time to separate the two, they actually represent the beginning and end of the process: the first notification indicates the app is checking an exposure, and the second indicates it has been checked.

The first notification is the one that has been present since the app launched.

“Possible Covid-19 exposure,” it reads.

“Verifying exposure info. The app has accessed the date, duration and signal strength of this exposure.”

This first notification appears to have been added to the app in the interests of transparency, and so that people know when their data is being accessed. It is a part of the Google and Apple technology that serves to link up the Bluetooth exposure information that is catalogued by the phone and the app’s technology that analyses and then makes sense of those exposures.

As the message suggests, but does not say explicitly, nothing about that notification is intended to encourage anyone to take action. It is purely informational, intended to make clear that the data has been accessed and that the app is using it, but does not require anything of the user when they see it.

That information comes later, in the form of a second notification – though it usually comes straight away.

“Covid-19 exposure check complete,” the second reads.

“Don’t worry, we have assessed your risk and there is no need to take action at this time. Please continue to stay alert and follow the latest advice on social distancing."

One of the things that makes this notification so strange is that there is no information accompanying it, and swiping onto it just takes the user back to the home page of the app. That is because it is intended primarily as a way to tell people there is nothing immediate to worry about, and as a way to assure the people who were becoming concerned when the app only showed the first notification, so there is in principle no new information to send them towards.

Of course, not everyone will receive this second notification. The app will sometimes perform the “covid-19 exposure check” and find that the data suggests the person might have been close enough to someone who has tested positive for long enough that they might be at enough risk to need to self-isolate.

If that happens, users will instead receive a different notification, telling them that is the case. Clicking through on that notification will take a user to extra information: guidance on self-isolation, as well as a countdown of how long there is left to wait.