12 May 2021

Covid-19 contract-tracing app ‘prevented at least 100,000 infections’

12 May 2021

The NHS contact tracing app for England and Wales prevented at least 100,000 Covid-19 infections between October and December last year, a new study suggests.

Researchers analysing data collected from the app estimate that somewhere between 100,000 and just over 900,000 cases of Covid-19 were prevented by the app’s exposure notifications.

The study, which has been published in Nature, says that the contract tracing app sent around 1.7 million exposure notifications in the last three months of 2020, as a result of 560,000 app users testing positive.

Coronavirus graphic (PA Graphics)

It estimates that around 6% of app users that receive a close contact notification will go on to report a positive test themselves – a similar rate to manual testing.

The research was led by a team from Big Data Institute, part of the Li Ka Shing Centre for Health Information and Discovery at the University of Oxford.

Using a mathematical model, the study authors then estimated the probability that notified contacts would be infected and quarantine in a timely fashion and as a result predicts that between 108,000 and 450,000 cases of Covid-19 were averted.

Further statistical analysis of the app data compared areas with similar demographics but with differing levels of app uptake suggest that the number of cases averted increased as app uptake also, with the research predicting that between 317,000 and 914,000 cases could have been averted during the study period.

The study authors suggest that although the two estimates differ they agree in the sense that the contact-tracing app holds value in reducing virus transmissions.

Their research also found that the average number of contacts traced by the app was more than double that of manual contact tracing, but the two systems can be complementary as they could help trace different contacts.

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