Even low uptake of contact-tracing apps found to save lives and reduce infection

Digital contact-tracing apps are able to save lives and help control the coronavirus epidemic with even just a small uptake of users, researchers from Oxford University and Google have said.

The latest study models the potential contribution of Exposure Notification Systems, a system that has been adopted by Google and Apple for implementation into their respective mobile operating systems.

The team looked at infections, hospitalisations, and deaths in Washington State’s three largest counties: King, Pierce and Snohomish.

They found that the more people use Exposure Notification Systems, the greater the reduction in Covid-19 transmissions, and the greater the opportunity to ease restrictive quarantine measures.

Furthermore, they said that “all levels” of exposure notification uptake levels in the UK and the USA have the potential to “meaningfully reduce the number of coronavirus cases, hospitalisations and deaths across the population”.

Professor Christophe Fraser, co-lead author, said: “We estimate that in Washington State, a well-staffed manual contact-tracing workforce combined with 15 per cent uptake of an exposure notification system could reduce infections by 15 per cent and deaths by 11 per cent.”

The team used Oxford’s epidemiological model OpenABM-Covid19 with the latest real-world data from Washington state on both the epidemic and on patterns of human mobility and social interactions.

They included different scenarios and outcomes which enable policy-makers to consider phased reopening and easing of Covid-19 restrictions, and so enable as many people as possible to return to more normal activities whilst maintaining control of the epidemic.

Dr David Bonsall, scientific advisor to the UK government’s Test & Trace Programme, said: “Covid-19 infects others before we develop symptoms, and some people transmit with only mild or no symptoms at all.

“Lockdowns and travel restrictions are damaging to society so we need smarter, more efficient systems that notify only the people at risk and keep the rest of us moving freely.

“Privacy-preserving digital exposure notification systems are an important part of the global response to this pandemic. They will save more lives and reduce increasingly more infections as people gain trust in the systems.”

The Google Research team added that targeted or phased reopening strategies should be considered, such as identifying specific occupation sectors or schools, and they hope the simulations will help public health authorities strike the balance between protecting people from infection and reducing the social and economic impact of prolonged or repeated lockdowns.

The research somewhat clashes with claims from a team at University College London last month who found that contact-tracing apps are of limited effectiveness when not combined with a package of other measures designed to slow the spread of the virus.

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