Scotland has developed a federated server that will allow for all Covid-19 contact-tracing apps in the UK, Crown Dependencies and Gibraltar to become interoperable.

Users of the Protect Scotland contact-tracing app will now be able to continue using it as they travel to Northern Ireland or Jersey. Protect Scotland will be able to interoperate with Northern Ireland’s StopCOVID NI and the Jersey COVID Alert app, and users of all three who have been in close proximity of each one another will be able to receive notifications of Covid-19 exposure.

An agreement has been reached so that the NHS COVID-19 app used in England and Wales and the Beat COVID Gibraltar app will join the same federated contact-tracing server in early November.

App users who travel between territories will not need to do anything to make this interoperability work, other than keep their existing app active.

Limited travel still paramount

Citizens are still being urged to travel between territories only for essential reasons, regardless of whether their contact-tracing app will now work or not.

In a statement, Scottish Health Secretary Jeane Freeman said: “While people are being advised to travel less at the moment, this compatibility will allow those having to travel for essential reasons to continue to be alerted via the Protect Scotland app if they have been in close contact with a positive Covid-19 case while in Northern Ireland or Jersey. There will be no need to download the Northern Irish or Jersey app, instead the Protect Scotland app will speak to those apps behind the scenes.”

The Scottish server has the potential to make it easier for other apps elsewhere in Europe and further afield to also work with Protect Scotland in the future.

“Agreement has been reached with England and Wales for the NHS Covid-19 app to become compatible in the coming weeks and we are working to ensure Protect Scotland is compatible with other European apps over time,” Freeman said.

Server issues and app updates

While Freeman noted that the apps will speak to the server behind the scenes, Zühlke UK CEO Wolfgang Emmerich, whose team helped develop NHS COVID-19, explains that this isn’t exactly the case.

“The apps don’t actually talk directly to that interoperability server, so there’s no change required to any app to achieve interoperability, but the backend systems do,” Emmerich says. “The purpose of that contact-tracing server is to basically exchange information about those people who’ve tested positive, so that other nations can then inform people across borders that they might have been exposed.”

The backend system of an app is much like a server for mobile apps, which stores and sorts the important information that the end user does not see.

Emmerich was also able to explain the ‘phantom’ notifications that many NHS COVID-19 app users have been receiving.

Since launch, many NHS COVID-19 users have been receiving notifications which suggest they’ve been in close contact with someone who has tested positive for Covid-19, only to have the notifications disappear when clicked on. This was eventually addressed by the introduction of follow-up notifications explaining that the first one should be ignored, but many users understandably find them disconcerting.

Emmerich says: “What happens there is that you have in fact been within Bluetooth signal range of somebody who has tested positive. We then measure the signal strength and based on the weakness of the signal decide that you haven’t been close enough to have picked up anything, but it is a near-miss.”

A soon-to-be-released update to the app will switch to a new version of Google and Apple’s exposure notification application programming interface (API) and will no longer issue these confusing notifications.