Question to the Department of Health and Social Care:

To ask Her Majesty's Government what assessment they made of the benefits of using a (1) centralised, and (2) decentralised, model for the COVID-19 contact tracing application; which of those benefits they plan to realise from the model in use; and what plans they have, if any, to change the model should those benefits not be realised.

Our priority has been to maximise the public health value of the app to save lives, while preserving privacy. We have gone for a centralised model because it provides the most flexibility from an epidemiological and disease management point of view.

Our centralised approach for the app gives the National Health Service a clear picture of which phones have been in close contact with each other. The model allows us more flexibility in how we decide to notify users and will help us give the most accurate advice to individuals. This flexibility will help to better spot false alarms and unnecessary alerts asking people to self-isolate.

We continue to work with Apple and Google to deliver the NHS COVID-19 app. The app will continue to evolve as our understanding of the virus increases and we will continue to revisit our design decisions as that understanding grows and we move to a national roll out.