Contact tracing apps — a sad postscript?

As I finalise a book chapter on the UK (England in particular) experience with Covid contact tracing / exposure notification apps, Boris Johnson’s government is sadly generating a downbeat postscript on a technical intervention that was well-meant, even if considered by many experienced eyes as “technology theatre” from the start. Feel free to contact me personally for a chapter preprint, but given the timeliness and (limited) opportunity to improve the situation at this point, here is the postscript. Thanks as always for the great real-time feedback from colleagues on Twitter and Signal as I drafted this!

As this chapter was finalised in early July 2021, the UK suffered a third (and hopefully final) wave of tens of thousands of daily infections even as vaccination coverage and post-infection immunity came very close to herd immunity levels, propelled by the highly infectious Delta variant of Covid-19. This coincided with government determination to lift all legal requirements in England on 19 July for social distancing, mask wearing, self-isolation, and other non-pharmaceutical interventions (Allegretti and Geddes 2021). There were fears from academics and the media of a “super-exponential growth phase” (Greenhalgh 2021) and up to 10 million people being notified over six weeks they should self-isolate following contact with a confirmed case (Walker and Stuart 2021).

Such conditions would be ideal for an automated contact tracing system to demonstrate its advantages over a manual contact tracing programme, which even with a total government budget of £13.5bn spent by NHS Test and Trace in 2020-21 could not remotely cope with this number of cases in the UK. During the second wave of infections in December 2020, even the timely test results test-and-isolate systems rely on fell to 17% received within 24 hours (Torjesen 2021). However, the soaring number of third-wave exposure notifications sent instead provoked media calls to “ping off”, with complaints of “house arrest” and cynicism about compliance rates (understandable given the extremely limited financial support given to those self-isolating), alongside politicians apparently determined to demonstrate they made these laws for others to follow (Purves 2021).

As in the United States, although to a lesser degree, UK mask-wearing became significantly politicised during the pandemic, with government ministers declaring they could barely wait to stop wearing them after “freedom day” on 19 July 2021. A tracing app widely seen to be inaccurate and opaque, advising tens/hundreds of thousands of individuals to self-isolate, from an increasingly distrusted government (Purves 2021), runs a significant risk of becoming similarly politicised. 

It was therefore particularly alarming that the tracing app’s designers struggled to update the software given the changing risk parameters of multiple Covid variants of concern spreading throughout the UK in late 2020 and 2021, or even to update the app to adjust these parameters for vaccinated users (both their own reduced risk of infection, and their reduced risk of infecting others.) One academic adviser to the programme worried “the people who actually built the serious risk model in the successful app have left…so the team may not have the skills to update the system to include other risk factors (new variant & vaccination)” (Crowcroft 2021).

As always, maintaining a clear understanding of the sociotechnical environment in which a technology is deployed – alongside social and economic interventions essential to its success, such as financially supporting those who cannot otherwise afford to self-isolate – is critical if it is to have any hope of achieving its goals. 

Aubrey Allegretti and Linda Geddes (2021) PM to confirm 19 July end to Covid rules despite scientists’ warnings, The Guardian (July 4). 

Jon Crowcroft (2021) Personal communication (July 5).

Trish Greenhalgh (2021) Freedom Day, but at what cost? The BMJ Opinion (July 6).

Libby Purves (2021) It’s time for NHS contact tracing to ping off, The Times (July 5).

Ingrid Torjesen (2021) NHS Test and Trace: lack of progress is “deeply disappointing”, British Medical Journal 373:n1636.

Peter Walker and Heather Stuart (2021) Data predicts 2m UK summer Covid cases with 10m isolating, The Guardian (July 6).