Less than 8% of people who have tested positive for COVID-19 in Colorado since October have used a state-sponsored smartphone app to let people know they may have been infected, but it may still have helped to avoid additional cases.
About 2.1 million people in Colorado have downloaded the app developed by Google and Apple, which exchanges tokens over Bluetooth with nearby phones that have also downloaded and activated it.
If a person tests positive for COVID-19, they are given a code that they can use to send an anonymous notification to other people that person may have exposed. The app tries to determine the risk based on how close the person – or at least their phone – to other people, how long they’ve been around, and how contagious the sender is, depending on the day the symptoms started.
The Colorado Department of Public Health and Environment reported that it generated 377,007 codes for anyone who tested positive between October and mid-June, and 29,183 people were using them to notify others that they could have infected.
Some of the people who tested positive may not have gotten the app, while others may have chosen not to enter the notification code. A few Coloradans said they had never received a code from the state, although it was not clear whether the problem was widespread.
At least 103,689 people have received notifications that someone they had been close to during the time that person may have been contagious had tested positive for COVID-19, but it is not known how many more were exposed but not notified.
Many states have used essentially the same app, with their underlying health department information. It was created by Google and Apple, and the two tech giants haven’t charged states for using it. It is available for free to Android users from the Google app store, and Apple users with recent iPhone models have had the option of using it as part of a software upgrade.
“We know that thousands of people have anonymously shared their positive diagnosis through the service, allowing other users they have come in contact with to initiate testing and quarantine protocols as soon as possible,” the department said. state health in a statement. “Colorado is proud to have been a pioneer in the use of this technology, and we believe the service will continue to support our COVID containment efforts as more Coloradans get vaccinated.”
It is difficult to be certain of the comparison of the use of the application by the Coloradans. A study in Washington state found that almost 10% of codes were used to notify contacts, but most states did not release their data.
It is even more difficult to know how successful an app was in preventing additional cases.
For this to work, a person who gets COVID-19 must have the app, get tested, receive a verification code, and send it. Then people who might have been exposed must also have the app and follow the quarantine instructions – something not everyone can easily do, given that it could mean missing two weeks of work. And, of course, some people who pose as contacts weren’t actually infected, so notifying them doesn’t prevent new cases.
Colorado has not attempted to quantify which cases have been prevented, but studies in other places have found wide possible ranges, depending on what they assume about the number of infected contacts and how they followed the quarantine rules. A study in UK discovered that the app could have prevented 100,000 to 900,000 cases.
The UK study also found that the app notified about twice as many contacts as traditional tracing, possibly because people forget who they’ve seen recently or haven’t exchanged names with everyone. However, use of the app was spotty, meaning people in some places were more likely to see it as a benefit than others.
It is not shocking that people who had more confidence in public health had more likely to download the appsaid Susan Landau, professor of computer science in the School of Engineering at Tufts University. But since those with the highest levels of trust tend to be white and relatively well-off, the app may have been less effective for essential workers who were at increased risk of contracting the virus.
When health services do traditional contract finding, they usually start by asking if the person can safely self-isolate at home and if they need help obtaining food or other essentials. necessity, said Landau.
“Only after doing the kind of thoughtful things do they move on to who could you have exposed,” she said.
Apps ignore this, so people may never know which media would help them isolate themselves safely until they are no longer contagious, Landau said. The biggest successes have been those that have linked an app to supporting people in quarantine, she said.
An app “can be very useful, but if you want it to work for the whole population, you have to support the isolation capability,” she said.
Normally, the use of apps and other new technology starts with a relatively small group of people and then spreads as more people see the benefits and want to take advantage of them, said Joanna Masel, researcher in ecology and evolutionary biology at the University of Arizona. It’s not practical for states that urgently need a tool during a pandemic, but small communities like universities have shown some of the best results, she said. About 25% of University of Arizona students who tested positive informed their contacts through an app.
Apps are not perfect, because they have to try to estimate when a person who recently tested positive became infectious, and cannot explain whether people were wearing masks, ventilating in a space and whether they were engaged in riskier activities, such as having a conversation close, Masel said. Still, studies suggest they are reducing the number of people the virus is spread to, she said.
“This alone is not enough. You have to have things like vaccines and masks, ”she said. “It’s enough around the edges to make the difference.