Part of the criticism could be due to an excessive amount of hype. The early concentrate on contact tracing apps was understandable: a vaccine remains many months away, assuming we can even find the one that will work. Apps stepped in to the breach as a potential panacea—even though many insiders have consistently argued they are just one of several tools we must fight herpes.
On a mathematical level, too, the low degree of notifications could be expected, based on Jon Crowcroft, professor of communications systems at the University of Cambridge. In a situation where there are low variety of covid-19 cases, people are observing social distancing, and the density of app users isn’t high, you’d not expect to see many notifications, that he says.
“It’s simple math for the numbers of notifications: if 1% of people have covid-19 and they are all tested, and only 1% of people run the app, you have a 1 in 10,000 chance of having both the tested person and the exposed person having the app, so your notification rate will be 10,000 times lower than the case rate,” Crowcroft explains. (For example, during the period in which Victoria issued 21 notifications, hawaii registered just 350 cases of covid-19.)
However, even with probably the most optimistic lens, it’s clear there’s a gulf between what was promised and what these apps are delivering. So what went wrong?
First, it’s worth looking at the similarities involving the two services. Both France and Australia shunned the model submit by Google and Apple—where data is kept on the user’s phone to maintain privacy—in favor of a centralized approach, where user information is delivered to remote servers. This is problematic because Google and Apple have restricted just how much Bluetooth scanning centralized apps can do in the background.
Michael Veale, a digital policy lecturer at University College London, sums up the matter: “They aren’t detecting many phones because the background Bluetooth does not function. That’s because they aren’t using a decentralized approach.”
This situation has generated a series of other technical difficulties. Australia’s app works only 25% of that time period on some devices, particularly iPhones. That’s because the Bluetooth “handshake” required to register proximity between two phones doesn’t work if the phone screen is locked. This was the exact problem that caused the UK to abandon its app last month (it’s not clear when it will launch a replacement).
“This effectively means for a contact tracing app to work without using their system, a user has to walk around like a Pokemon Go player, with their phone out, the app open, and not use their phone for anything else,” says one researcher in a roundabout way involved in development for either app, who requested anonymity.
All this may have now been exacerbated by adopting an overly conservative approach to steer clear of the risk of “over-notifying” users, says Crowcroft. Worries that oversensitive alerts could create panic means the apps only consider those who are excessively likely to have been around in close connection with each other for extended periods of time—not just people you brushed past for a couple seconds in the store. “A lot of care went into trying to avoid a lot of false positive notifications in some apps. This may make them super conservative,” that he says.
In addition, both Australia’s and France’s apps have now been blighted with performance problems and bugs. Users have complained that France’s app drains their phone’s battery life—possibly the main reason that thousands and thousands of people have uninstalled it.
“This is the prime risk for developers: you make one mistake and wipe out somebody’s battery,” says Andrew Eland, who until recently worked being an engineering director at Google and then DeepMind Health. Some users say the StopCovid app regularly crashes, and it has to be reactivated each and every time you switch your phone back on.
Aiming for improvement
So what are the lessons? Bluetooth is a highly complex technology, but it’s fiendishly difficult to construct a contact tracing app without using Apple and Google’s system. So for the sake of building an app rapidly, perhaps it’s most useful that governments don’t adopt a centralized system or something else that creates technical difficulties. If possible, countries should consider reusing the code for still another country’s app that has became a success—for example, Germany’s open-source Corona-Warn App, that has been downloaded by over 15 million people in a citizenry of 83 million because it launched on June 15. Secrecy and clinging to exceptionalism are a poor combination when it comes to building contact tracing apps.
And fundamentally, the public has to bear in mind that contact tracing apps are apt to be only a small part of the fight the coronavirus—rather than a magic answer to the problem.
“If you want to know the best way to spend time and money on technology to track and trace coronavirus infections, it would probably be better to focus on making manual contact tracing more efficient,” says Eland.