Holding answer received on 16 June 2020
The National Health Service COVID-19 app is designed to work as part of a wider approach to testing and contact tracing that aims to benefit everyone. The app will have a positive impact at any level of uptake.
All the evidence shows that even at lower levels of use, the app can help reduce the rate of transmission - but the more people who download and use the app, the more effective it will be. We are working closely with Oxford University and The Alan Turing Institute to continue modelling effectiveness at different levels.
We are working hard to ensure alignment between the app and the traditional measures of contact tracing so that they complement each other and work together to protect vulnerable groups and those who are unable or do not wish to use digital tools.