This story was originally published by The Colorado Sun at 3:43 AM on May 8, 2023.
It’s time to say RIP to Exposure Notifications, that thing on your phone that, if you enabled it, would sometimes buzz and tell you that you had been near someone who later tested positive for COVID-19.
The service is ending in Colorado on Thursday, according to the state Department of Public Health and Environment. Users will receive a notice on their phones saying that the service is no longer operational and a prompt to delete their app data.
The timing is related to the end of the federal public health emergency for COVID, which also falls on the 11th. A CDPHE spokesman said Apple and Google, which worked together to build the program, are “decommissioning” the service in Colorado. Similar shutdowns of state contact-tracing apps are occurring across the country.
Millions of people in Colorado enabled the app on their phones, allowing them to either send a notice to recent close contacts about a positive COVID test or to receive such a notice from somebody else. The idea was to automate the contact-tracing process, allowing people who test positive to more easily inform those who were exposed.
Contact-tracing — the strategy of telling people who have been exposed to a virus to quarantine so they don’t spread an infection further — is an age-old public health technique. But Exposure Notifications gave it a modern twist for the digital age.
Beth Carlton, a professor of epidemiology at the Colorado School of Public Health, said a digital approach to contract-tracing had the potential to be especially helpful for COVID because the virus has two tricks that often stymie more traditional public health efforts. First, it can be spread by people before they have symptoms or by people who never showed symptoms at all, making it difficult for those who are infected to avoid exposing others in public places. And, second, it can spread so rapidly that it can overwhelm manual contact-tracing efforts.
A digital approach in theory addresses both problems by allowing people to notify close contacts of an infection, even if they don’t know who their close contacts are, and by automating the process, allowing contact-tracing efforts to scale with rising infection numbers.
Carlton said the key has always been getting people to actually use the apps.
“The real tension with the digital contact-tracing apps is this uptake piece,” she said.
How many people in Colorado used Exposure Notifications?
Exposure Notifications arrived in Colorado in the fall of 2020, more than six months into the pandemic.
Users needed to either enable the functionality on their phone or to download an app, depending on what operating system their phone used. After that, the app used Bluetooth technology to exchange anonymous tokens with nearby phones. When someone using the app tested positive for COVID, they could send out an alert to everyone whose phone their phone recently exchanged tokens with.
According to CDPHE, more than 4 million devices in the state enabled Exposure Notifications — it’s unclear how many people did because one person could have enabled it on multiple devices.
The agency said Coloradans used the app to send notices about 201,000 positive COVID tests. Those notices went to nearly 2 million people, according to CDPHE.
Did Exposure Notifications actually prevent COVID infections?
The app’s effectiveness in limiting COVID transmission is unclear.
Asked for data on the app’s impacts in Colorado, CDPHE instead provided a link to a Centers for Disease Control and Prevention study on use of the Exposure Notifications in Pennsylvania. The study concluded that digital notifications potentially averted between seven and 69 new COVID cases for every 1,000 notifications sent. If that is true, then it extrapolates to Exposure Notifications averting as many as 138,000 COVID infections in Colorado.
But the evidence so far is not conclusive.
Carlton said there have been a number of studies on the apps published across the globe, and the results are a bit mixed. One study in Australia looked at a smartphone-based app in that country called COVIDSafe and found that low uptake hampered its usefulness.
“COVIDSafe was not sufficiently effective to make a meaningful contribution to the COVID-19 response,” the study concluded.
A study looking at a smartphone-based contact-tracing app used in England and Wales, though, found that the app may have averted up to 1 million COVID cases.
“We conclude that digital contact tracing has played an important role in reducing transmission of SARS-CoV-2 in England and Wales in practice,” the authors of that study wrote.
Carlton said one crucial element of the England and Wales study is that the app was multifunctional and could also be used to show proof of a recent negative COVID test to be allowed into public venues. That increased the app’s uptake.
There are also other elements that impact the apps’ effectiveness. Carlton said people must be willing to follow instructions and quarantine after receiving an exposure notice — and it’s not clear they always did.
Carlton mentioned what some took to calling a “pingdemic” — basically an alarm fatigue that the apps could create. The more the apps were used to notify contacts of potential exposure, the more alerts people received, the more they may have been inclined to brush them off.
“I’m imagining many people had the experience of getting the notification and saying, ‘I don’t know anyone who is positive’ and they probably ignored it,” Carlton said. “I feel like this goes back to the central theme of SARS-CoV-2, which is human behavior — the hardest thing to influence.”
What comes next for digital contact tracing?
Colorado is currently enjoying one of its deepest COVID lulls since the start of the pandemic.
Reports of new COVID cases are averaging below 200 per day in Colorado, which is as low as it’s been since the summer of 2020. At-home testing, of course, means that a lot of cases are probably going unreported. There are about 130 people hospitalized with COVID infections right now in Colorado, with the infection being the primary reason for admission in about two-thirds of those cases.
This fits with seasonal patterns generally observed throughout the pandemic. But that same seasonality also suggests we could be in for another fall wave of infections. And, if that happens, would we miss not having Exposure Notifications around?
CDPHE has dismantled its large-scale contact-tracing efforts. Manual contact-tracing efforts now fall on the shoulders of local public health departments, where resources can vary greatly and which are vulnerable to being overwhelmed by infection surges.
Carlton said whether to continue using public health resources and strategies developed for the toughest moments of the pandemic has been an ongoing debate. Take masking, for instance. On one hand, why not just keep telling people to mask indefinitely if it could prevent infections? But, on the other hand, if what you really want is high mask use during the biggest waves of infection, maybe the best way to persuade people to do that is to tell them they only need to wear a mask for a limited time.
She sees the same struggle when it comes to the contact-tracing apps, which come with their own questions of privacy and necessity, along with their potential to avert infection.
“It is this really interesting puzzle of, in the fall, are we going to ask to pull out apps like these?” Carlton said. “And, if not, what will the strategy be?”
