Why Apple and Google’s Virus Alert Apps Limited Success

Sarah Cavey, a real estate agent in Denver, was thrilled last fall when Colorado introduced an app to warn people of possible coronavirus exposures.

Based on software from Apple and Google, the state’s smartphone app uses Bluetooth signals to detect users who come into close contact. If a user later tests positive, the person can anonymously notify other app users whom the person may have crossed paths with in restaurants, on trains or elsewhere.

Ms. Cavey immediately downloaded the app. But after testing positive for the virus in February, she was unable to get the special verification code she needed from the state to warn others, she said, even after calling Colorado’s health department three times.
“They advertise this app to make people feel good,” Ms. Cavey said, adding that she had since deleted the app, called CO Exposure Notifications, in frustration. “But it’s not really doing anything.”

The Colorado health department said it had improved its process and now automatically issues the verification codes to every person in the state who tests positive.

When Apple and Google announced last year that they were working together to create a smartphone-based system to help stem the virus, their collaboration seemed like a game changer. Human contact tracers were struggling to keep up with spiking virus caseloads, and the trillion-dollar rival companies — whose systems run 99 percent of the world’s smartphones — had the potential to quickly and automatically alert far more people.

Soon Austria, Switzerland and other nations introduced virus apps based on the Apple-Google software, as did some two dozen American states, including Alabama and Virginia. To date, the apps have been downloaded more than 90 million times, according to an analysis by Sensor Tower, an app research firm.

But some researchers say the companies’ product and policy choices limited the system’s usefulness, raising questions about the power of Big Tech to set global standards for public health tools.

Computer scientists have reported accuracy problems with the Bluetooth technology used to detect proximity between smartphones. Some users have complained of failed notifications. And there is little rigorous research to date on whether the apps’ potential to accurately alert people of virus exposures outweighs potential drawbacks — like falsely warning unexposed people, over-testing or failing to detect users exposed to the virus.

“It is still an open question whether or not these apps are assisting in real contact tracing, are simply a distraction, or whether they might even cause problems,” Stephen Farrell and Doug Leith, computer science researchers at Trinity College in Dublin, wrote in a report in April on Ireland’s virus alert app.

In the United States, some public health officials and researchers said the apps had demonstrated modest but important benefits. In Colorado, more than 28,000 people have used the technology to notify contacts of possible virus exposures. In California, which introduced a virus-tracking app called CA Notify in December, about 65,000 people have used the system to alert other app users, the state said.

“Exposure notification technology has shown success,” said Dr. Christopher Longhurst, the chief information officer of UC San Diego Health, which manages California’s app. “Whether it’s hundreds of lives saved or dozens or a handful, if we save lives, that’s a big deal.”

In a joint statement, Apple and Google said: “We’re proud to collaborate with public health authorities and provide a resource — which many millions of people around the world have enabled — that has helped protect public health.”

Based in part on ideas developed by Singapore’s government and by academics, Apple and Google’s system incorporated privacy protections that gave health agencies an alternative to more invasive apps. Unlike virus-tracing apps that continuously track users’ whereabouts, the Apple and Google software relies on Bluetooth signals, which can estimate the distance between smartphones without needing to know people’s locations. And it uses rotating ID codes — not real names — to log app users who come into close contact for 15 minutes or more.

Some health agencies predicted last year that the tech would be able to notify users of virus exposures faster than human contact tracers. Others said they hoped the apps could warn commuters who sat next to an infected stranger on a bus, train or plane — at-risk people whom contact tracers would not typically be able to identify.

“Everyone who uses the app is helping to keep the virus under control,” Chancellor Angela Merkel of Germany said last year in a video promoting the country’s alert system, called Corona-Warn-App.

But the apps never received the large-scale efficacy testing typically done before governments introduce public health interventions like vaccines. And the software’s privacy features — which prevent government agencies from identifying app users — have made it difficult for researchers to determine whether the notifications helped hinder virus transmission, said Michael T. Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

“The apps played virtually no role at all in our being able to investigate outbreaks that occurred here,” Dr. Osterholm said.

Some limitations emerged even before the apps were released. For one thing, some researchers note, exposure notification software inherently excludes certain vulnerable populations, such as elderly people who cannot afford smartphones. For another thing, they say, the apps may send out false alarms because the system is not set up to incorporate mitigation factors like whether users are vaccinated, wearing masks or sitting outside.

Proximity detection in virus alert apps can also be inconsistent. Last year, a study on Google’s system for Android phones conducted on a light-rail tram in Dublin reported that the metal walls, flooring and ceilings distorted Bluetooth signal strength to such a degree that the chance of accurate proximity detection would be “similar to that of triggering notifications by randomly selecting” passengers.