Tests of a second version of the NHS’ coronavirus contact-tracing app have found flaws in the way technology developed by Apple and Google detects nearby devices, the government has said.
The NHS last week abandoned the first version of the app and health secretary Matt Hancock has declined to say when another version might be ready.
The first iteration, developed without the smartphone giants’ built-in Exposure Notifications framework, registered about 75 percent of nearby Android phones but only 4 percent of iPhones.
A second version, which uses the Apple and Google technology, logged 99 percent of both types of phones but produced inaccurate distance calculations, officials said.
The newer version was unable to to distinguish a phone in someone’s hand three metres away from a device in someone’s pocket one metre away, they said.
The distance calculations are crucial because they are used to determine whether someone has been in close enough contact to have transmitted the novel coronavirus.
As a result, they would be used in determining when to alert someone that they should self-isolate.
“Measuring distance is clearly mission critical to any contact-tracing app,” Hancock said during a briefing on Friday.
Apple said it was unaware of the distance-logging issue and said the government hadn’t communicated its concerns.
“It is difficult to understand what these claims are as they haven’t spoken to us,” the company told the Times.
Apple pointed out that the technology was being used by apps in Germany, Italy, the Netherlands and Ireland with “no issue about proximity detection”.
The NHS’ initial app was not able to use the built-in Exposure Notifications technology due to the iPhone’s privacy protections.
These were incompatible with the NHS app’s “centralised” model, in which data is processed on a government server.
Apple and Google’s technology requires that all data be processed on individual devices to protect privacy.
Hancock said the government would work with the US tech companies to “bring the best bits of both systems together”.
But Apple said it wasn’t aware of such a “hybrid” model.
“We don’t know what they mean by this hybrid model. They haven’t spoken to us about it,” the company said.
The Department of Health said the NHS’ technology division, NHSX, had been working with Apple and Google “extensively”.
“NHSX has been working with Google and Apple extensively since their API (application programming interface) was made available,” the department said in a statement.
It said senior representatives from NHSX and Apple had had “productive meetings” and that there is a “commitment” between the teams to work together to improve the distance-measurement technology.
Google has said it welcomes the government’s switch to the company’s built-in notifications framework.
Privacy advocates have said “centralised” contact tracing apps are too invasive of privacy, and Norway’s data protection regulator earlier this month shut down the country’s app due to such issues.