On Monday, the deputy chief medical officer, Jonathan Van Tam, said high take-up of the app was crucial to its success, adding: “We do have some uncertainties about how many people will download the app.
“It will be important that a significant proportion of the population downloads the app for it to have the greatest chance of giving us additional ‘oomph’ in the contact tracing space, which in turn will give us additional room for manoeuvre in terms of other social distancing easements that we can consider in the weeks and months to come.”
Health officials insisted concerns about privacy and security have been addressed, and Mr Gould said: “We’ve put privacy right at the heart of it and the way it works. The app is designed so that you don’t have to give it your personal details to use it. It does ask for the first half of your postcode, but only that.
“So you can use it without giving any other personal details at all. It doesn’t know who you are. It doesn’t know who you’ve been near. It doesn’t know where you’ve been – rather, what it does is assigns randomised identifiers to its users.”
Mr Gould said all the detail stays on the phone until people become symptomatic and get an option to upload their information. Even when individuals upload their details, those who have been in contact with them would not be given the identify of the person who may have exposed them to risk, he stressed.
Professor Van Tam said there was “significant optimism” that high numbers of people would engage with the app. Officials said it has yet to be decided whether children will be included in the national app.
A spokesman for NHSX said the National Data Guardian panel had been consulted on the plans and the data collected by the app would only be used for NHS care, evaluation and research. An independent assurance board involving experts in mobile apps, data governance and clinical safety has also been set up to monitor production of the app.
The spokesman said apps were not normally assessed for the app store during the earlier stages of testing and, although it has been asked to carry out early assessments already, further reviews would take place after the piloting.