August 5, 2021

expert reaction to latest weekly NHS COVID-19 app statistics

The NHS have published the latest weekly statistics on the NHS COVID-19 app, showing a decline from last week in the number of contact tracing alerts sent.

Comment updated 05/08/2021 to correct dates between which the number of people pinged by the NHS COVID-19 app declined by 43%: Prof Christophe Fraser, Senior Group Leader in Pathogen Dynamics at Oxford University’s Nuffield Department of Medicine and scientific advisor to the Test and Trace Programme, said:

“The number of people pinged by the NHS COVID-19 app declined by 43% between the week of Thursday 15 July – Wednesday 21 July and the week of Thursday 22 July – Wednesday 28 July (the most recent data we have, released today).

“The main reason that this has happened is that there are fewer cases.

“Overall, the number of pings closely tracks the number of cases, the number of active users, and the contact rate of users.

“The main driver of changes in pings over recent weeks has been the change in the number of confirmed cases of the disease.

“Controlling the epidemic means that fewer people become ill, and fewer people are disrupted by being pinged.

“The app is one of the tools that reduces the number of people who get infected.

“We are investigating the extent to which the peak of notifications, or ‘pingdemic’, was one of the causes of the recent decline in cases, alongside the start of the school holidays.

“You can read more about our work in this area here: https://www.coronavirus-fraser-group.org/blog, and we have created a dashboard to see some of the official data from https://stats.app.covid19.nhs.uk/ here: https://bdi-pathogens.shinyapps.io/NHS-COVID-19-app-statistics/.”

Prof Jon Crowcroft FRS FREng, Marconi Professor of Communications Systems in the Computer Laboratory, University of Cambridge, said:

“There’s a drop in PCR positive tests, hence there’s a drop in pings.  Pings went up when the PCR positive tests went up, and now the PCR positive tests have gone down, the pings have gone down, which supports the idea that the app is actually working quite well.”

Prof Paul Hunter, Professor in Medicine, The Norwich School of Medicine, University of East Anglia, said:

“At its peak on 17th July there were 50,955 new cases reported, a week later there were 28,968 new cases – a 43% drop in new cases in just one week.  So the primary reason for the fall in pings is the big drop in cases.  There may have been some additional impact of people disabling that aspect of the app but the main reason is the drop in cases.”

Dr Philip Scott, chair of the health and care executive at BCS, The Chartered Institute for IT, and Reader in Health Informatics at the University of Portsmouth, said:

“The app tweak is good because it brings it into line with Test & Trace, but it raises the obvious question around why was it ever different as it may have led to many pointless alerts.  So yes, people are either uninstalling it or just not running it, according to the data that shows venue check-in plummeting.  Overall the app has served a purpose, but there is a need to challenge why its policy basis, of legal enforceability, was different to Test & Trace and why the alerting algorithm was not the same.  This is one example that shows why better professional IT standards should be more closely followed when it comes to apps and algorithms that affect our daily lives.”

https://stats.app.covid19.nhs.uk/

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