Credit: Hackney Council/Open Government License v3.0
Senior officials said it was ‘not possible’ to know how many people have activated the NHS Covid-19 contact tracing app.
Since its launch in England and Wales 13 months ago, the software has been downloaded almost 28.5 million times. But data has previously suggested that a significant proportion of users have not activated the program’s contact tracing capability and other key functions.
In April – when the app had been downloaded a cumulative total of 23.3 million times – government data said only 16 million users “had the app fully or partially activated on their phones”. And even that reduced number included “users who chose to disable contact tracing because the in-app on/off toggle is a feature designed to allow users to disable contact tracing as instructed, such as when storing their phone in a locker”.
Since then, all signs point to an even more widespread deactivation or removal of the app; as cases have held steady or increased, the number of contact tracing alerts issued each week has steadily declined.
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Over the summer, Parliament’s Public Accounts Committee asked Dr Jenny Harries, chief executive of Britain’s recently created Health Security Agency, to provide updated figures on how many people have activated the app.
His response, sent jointly with the Permanent Secretary to the Department of Health and Social Care, Sir Chris Wormald, said the government now believes it cannot produce a reliable estimate.
“There is no single definition or established measurement of a user who has activated the app,” says the letter, dated August 4 but released by the committee yesterday. “Some people may temporarily suspend contact tracing because there are several situations in which we advise temporarily suspending contact tracing, including if the user is a healthcare professional working in a healthcare building such as a hospital, or if someone works behind a Perspex screen and is fully shielded from others. Due to these limitations and the privacy-preserving design of the app, it is not possible to make a reliable and consistent count of people with the app enabled at any given time. »
In the week in which almost all remaining restrictions on businesses and citizens were lifted, the app alerted 679,445 people in England that they had been in close contact with someone who was subsequently tested positive for coronavirus. It happened in a week when 307,758 positive tests were recorded across the country.
The number of weekly exposure notifications fell sharply from that point on, and over the past month or so has stabilized around 120,000 to 130,000.
The most recent statistics, for the seven-day period ending October 13, show that 132,036 exposure notifications were sent by the app, while 257,196 people tested positive.
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