Launched over a year ago as a high-tech answer to California’s contact-tracing woes, the “exposure notifications” smartphone app for COVID-19 is still not being used by most people who test positive for the virus to warn close contacts of potential infection, data show.
The CA Notify app also does not yet have an option for people who test positive at home to share their diagnosis. That means thousands of infected people who want to anonymously alert others have no easy way to do so.
Social science and public health experts said the contact-tracing tool has potential but thus far has failed to live up to expectations — especially in a tech-savvy state where more than 4 million people have tested positive since CA Notify launched.
The reasons for the underwhelming use stem from problems that are sometimes highly technical and other times profoundly human.
Exposures to the highly transmissible omicron variant are likely going undetected because of the app’s limited definition of “exposure,” some say. The lack of options to report at-home test results also means a huge number of alerts aren’t being sent.
And many of those who initially signed on to the program have forgotten about it, in part because the notifications program has not been promoted as intensely as other public health campaigns such as vaccines and masking.
“I just think this is a tragically sad, but beautiful, case study of how tech with great promise doesn’t meet its potential to really do lots of good,” said Richard Carpiano, a sociology and public health professor at the University of California, Riverside.
That’s not to say the app has done nothing.
The CA Notify app has been downloaded more than 15.6 million times since Gov. Gavin Newsom announced it in late 2020. Since then, an estimated 160,000 California users who tested positive have sent alerts to some 700,000 people, said Dr. Chris Longhurst, chief information officer with UC San Diego Health.
“Without a question, this has avoided infections and saved lives,” said Longhurst, whose team has a $4 million contract with the state to administer the app. He said the program has broken thousands of chains of transmission and “exceeded our expectations.”
That said, Longhurst acknowledged the frustrations about the lack of at-home test reporting. If someone was infected during the holidays, flew on a plane and later tested positive with an at-home test, they’d have no way to send an alert to whoever they sat nearby and possibly infected. With hours-long lines at testing centers and appointments booked out a week or more, thousands of people who might have wanted to alert others have been left out.
The reason: California officials chose not to include an at-home testing option out of concern that people might erroneously input tests or distort the system.
An at-home attestation is in the works, Longhurst said last week — “Hopefully this month,” he said.
By comparison, Colorado in August began allowing users to report positive at-home tests through its app, which largely mirrors California’s.
There is no data to suggest widespread errors in reporting, said Kristen Stewart, a Colorado Department of Public Health and Environment spokesperson. An average of about 400 people daily in Colorado have reported positive at-home tests and triggered exposure notifications in the past two weeks.
Stewart called the app’s use “staggering.”
Developed by Apple and Google, the exposure notifications app does not track a user’s location, nor does it share a user’s identity. It uses Bluetooth technology to exchange random codes among users’ phones, whether on an airplane or in a restaurant.
If a user tests positive, the California Department of Public Health sends the person a verification code. When the user enters that into the app and launches notifications, they can trigger alerts to anyone whose phone was nearby and potentially exposed.
The notification app follows the CDC’s definition of what constitutes an exposure: 6 feet for 15 minutes. But disease researchers for months have said that guidance might be outdated for the more infectious delta variant — and especially for omicron.
Researchers know that COVID-19 is transmitted by aerosols, which can easily spread through a room. It would be better if apps defined exposure as simply being in the same space for a shorter amount of time, said Linsey Marr, an engineering professor at Virginia Tech who studies the airborne transmission of viruses.
“The apps are likely missing a large number of exposures,” Marr said.
While state officials can modify exposure zones, it’s unclear whether or when that will happen in California. In response to questions for this story, state officials said they monitor “emerging scientific literature to inform future revisions to CA Notify’s parameters.”
Challenges with the app go beyond defining exposure zones and at-home tests. Some people likely have no interest in sharing their health information with the government, regardless of how secure and anonymous the platform may be.
Such privacy concerns have made it difficult for program administrators to track its effectiveness. Officials don’t know exactly how many people sought testing after receiving an alert or how many later tested positive. It’s also unclear how many of the 700,000 notifications that people received went to individuals who were previously unaware of being exposed and how many, for example, went to family members in the same house as an infected person.
A recent federal report on exposure notifications systems in California and two dozen other states said states have only “a limited understanding of what impact, if any, these notifications have on disease spread.”
Regardless, said Longhurst, it’s one tool that has helped in a pandemic where contact tracing has been scattershot at best and oftentimes nonexistent.
“This is an incredibly low-cost intervention that’s having a real impact across the state,” Longhurst said. “Compared to a lot of other things, the cost of this is budget dust.”
The CA Notify app and others like it had a promotional problem from the start. After Newsom announced the app and touted California’s “innovative spirit,” banners pinged phones across the state and encouraged people to sign up. Millions did. By March, more than one-third of eligible cellphones in the state were believed to have been registered.
But that initial push quickly dropped out of public view, replaced by a massive effort to vaccinate Californians. Compared to other public messaging campaigns, details about CA Notify have been sparse, and many people likely forgot about the program altogether, said Andrew Noymer, an epidemiologist and associate professor of population health at UC Irvine.
Users online have reported confusion about the app. So have public health experts. Carpiano, the Riverside professor, is a prominent social scientist studying the pandemic. He remembered receiving the app a year ago but admitted he’d barely heard anything more about it.
Until a reporter contacted him for this story, he said he didn’t know that the user — not a health official — had to copy a code from a text message into the app after testing positive in order to send alerts to close contacts.
Carpiano called that a “big Achilles heel on the system.”
“Plugging stuff into an app is probably the last thing that you’re doing,” he said, noting the disruption to daily life that comes with a positive test. “The fact that we’re even having this kind of conversation, and I had to ask for clarification, I think in some ways that’s indicative of the issue.”
The process has become easier in recent months. CA Notify now has an automatic prompt, Longhurst said, that opens when someone tests positive and receives a message from the health department.
Plans are also in the works to create a public dashboard to better keep CA Notify data publicly accessible.
“There’s room for improvement,” said Dr. Eliah Aronoff-Spencer, a UCSD scientist working on the CA Notify project. “But it’s really on us to communicate to people this is valuable, that it belongs, and that for sort of the cost of nothing you can really save a life.”
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