Contact-tracing apps reduce transmissions and deaths even at very low levels of adoption, according to a new study from the University of Oxford and Google.
The study provides reassurance regarding the value of coronavirus contact-tracing apps, which some had suggested would need to be used by 60% of the population to be effective.
But the research emphasises that digital notifications to people who may have been exposed to the virus still work best when complemented by manual contact tracing, when researchers take histories from patients to find out who they had been in close contact with.
Professor Christophe Fraser of the University of Oxford explained: "We've been exploring different digital contact tracing uptake levels for some time in the UK.
"We see 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."
The vast majority of the study's authors worked for Google's parent company Alphabet, which alongside Apple has provided an exposure notification system during the coronavirus pandemic.
The study, which has not yet been peer reviewed, used a model based on three counties in the US state of Washington, and found even if just 15% of the population participated, this would result in an 8% reduction in infections and 6% drop in deaths.How does contact tracing work?
According to the models, if 75% of the population were to use the exposure notification system then transmissions and deaths could be reduced by 81% and 78% respectively.
Professor Fraser added: "The research results build on our previous findings in the UK and suggest a contact tracing app is not a stand-alone intervention."
Instead any such app "should be integrated and continually updated alongside other existing and new infection control measures, such as social distancing and restricted travel, until COVID-19 transmission is fully and sustainable under control."