Apple and Google have launched their toolkit, the Exposure Notification API, which will help public health agencies build privacy-focused coronavirus contact-tracing apps. The two companies have been collaborating for the past month to develop an API to support contact-tracing apps.

In the context of the coronavirus pandemic, digital contact tracing involves devices detecting and keeping a record of other devices running the app nearby, alerting users when one of their recent contacts reports that they have Covid-19.

This alert could advise the exposed user to get a test; to go into self-isolation, or take other precautions. Digital contact tracing is considered one of the pillars of lockdown loosening strategies by many governments, although contact-tracing apps must have a high level of public trust and take-up in order to be effective.

It is hoped that the toolkits provided by Apple and Google will go some way to resolving two major issues which could affect take-up of contact-tracing apps: the restrictions on third-party apps’ use of Bluetooth in the background, which forces iOS users to have the app open on their screen for it to work effectively, and the wider privacy concerns.

This new system uses a decentralised model which processes data on individuals’ devices rather than on a central server, among other privacy-focused measures, e.g. preventing an app developer from collecting location data. Apps incorporating the API should also be interoperable, meaning that contact tracing will not be interrupted when users cross borders between countries using this protocol.

In a joint statement, companies said that privacy is essential for digital contact tracing to be effective: “User adoption is key to success and we believe that these strong privacy protections are also the best way to encourage use of these apps,” they said.

Austria’s contact-tracing app will be among the first to incorporate the API in a 10 June update, allowing iOS users to let the app run in the background. The German contact-tracing app, expected to be launched soon, will also incorporate the Exposure Notification API.

Apple and Google said that they had already received requests to test the toolkit from 22 national public health agencies and several US states. The API is likely to be updated over the coming weeks and months to improve its effectiveness – for instance, to increase the frequency of the ‘listening’ for Bluetooth signals – and to patch any potential security vulnerabilities.

Google and Apple have indicated that apps using their API are not a replacement for manual contact tracing and other measures, such as enhanced hygiene, large-scale testing and social distancing.

The UK government and a handful of others – including the French and Indian governments – have decided to pursue centralised digital contact tracing, which processes data on a centralised server. The NHS’s innovation arm, NHSX, has argued that this will provide valuable insights which could, for instance, help hospitals prepare for an incoming local outbreak of cases.

However, amid a multitude of serious concerns about privacy, security and usability, NHSX is understood to be considering switching to the decentralised model supported by the Exposure Notification API.

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