The EU Commission has published a set of guidelines and Q&As on interoperability between member states’ contact tracing apps. Apps should be able to communicate with each other so that users can receive alerts wherever they are in the EU, without having to download multiple apps. The guidelines emphasise that interoperability between member states’ apps will be essential for tracing cross-border infections. This issue is likely to become more prominent as workers who commute to another country return to work.
Agreeing the technical details for interoperability is identified as a next step. This will not be straightforward, as member states have adopted different technical models for their national contact tracing apps. As the guidance points out, some apps require almost all data processing and storage to take place on the device, while other apps require more processing and storage on a back-end server. Member states such as Germany, Italy and Ireland have followed the decentralised approach, whereas France has taken a more centralised approach. Users will need reassurance that their privacy rights are being safeguarded when they travel between countries. Users who are willing to trust a decentralised app with their data may not feel the same about using an app which sends data to a central government server. Germany, for example, initially intended to take a centralised approach, but moved to developing a decentralised app after privacy concerns were raised. Winning over users of decentralised apps such as Germany’s to interoperability, where they may come within the jurisdiction of a centralised app such as France’s, may require careful planning.
EU Citizens should be able to rely on a single app independently of the region or Member State they are in at a certain moment.