In a move that marks a major U-turn for the Government, the UK’s proposals for a centralised contact tracing app have been abandoned in favour of a decentralised model. The new model is based on technology developed by Apple and Google and replaces the original app designed by NHSX, which recently has faced criticism due to privacy concerns as well as technical issues and delays.
The UK follows Germany and Italy, who have already made the switch from centralised contact tracing apps to decentralised models. The UK’s health secretary, Matt Hancock, confirmed the news at the UK Government press conference last night.
To centralise or decentralise?
The UK Government had previously asserted the superiority of a centralised contact tracing model, but what exactly is the difference?
A ‘decentralised’ data model requires individual users to provide an anonymous ID to a centralised server. The user’s phone then downloads information from the centralised database and carries out contact matching and risk analysis on the phone itself before sending alerts to other users if necessary. Information on whether a user has come into contact with an infected person will be shared with that user, but not with the central server.
In contrast, a ‘centralised’ data model would require users to provide not only their own anonymous ID to a centralised database, but also to send any codes collected from other phones. The computer server then carries out contact matching and risk analysis using that information, making the decision as to whether someone is ‘at risk’ and sending alerts accordingly.
The UK’s previous preference for the centralised model was based on the belief that storing data in a centralised manner would promote a more considered approach to contact tracing based on risk factors, and would enable epidemiologists to use valuable data on the spread of the virus for further research. However, the centralised model was criticised for potentially encroaching on privacy by using more data than necessary, and using the data for purposes other than contact tracing.
NHSX, the health service’s innovation arm, has confirmed that its current leaders will step back from the project, and that Simon Thompson, current chief product manager at Ocado, will take over management of the new app.
While this move will be welcome to privacy campaigners and critics of the centralised model, concerns over the limitations of Bluetooth-enabled technology, as well as the uneasiness over allowing Apple and Google to control the UK’s response to the pandemic, may cause further obstructions to the eventual rollout of a UK-wide contact tracing app. The additional delays resulting from this change in approach may also result in a lower than ideal take-up rate, with much of the population of the view that the time for contact tracing has passed given the current downwards curve of the pandemic.