Within weeks of Covid-19 shutting down the world in 2020, teams at archrivals Apple and Google partnered on a rare joint project. They developed a way to log people’s proximity using Bluetooth chips in iPhones and Android phones, enabling the creation of apps that let someone who tested positive for the virus to anonymously notify fellow users whom they'd been near in the preceding few days. Those alerted to the exposure could then isolate, test, and quarantine, hopefully slowing the spread of Covid.
Covid is still around, but the grand experiment in semi-automated contact tracing by smartphone is now nearing its end in the US, following similar shutdowns in many other countries as concerns about the virus have eased.
On May 11, the Biden administration will stop paying for the two cloud servers that underpin the US system and power exposure-tracking apps offered by individual states. States will now have to boot up their own servers, and in many cases redesign their apps, if they want to keep the alerts flowing. Though a few, including California, are considering the idea, it remains to be seen whether any will follow through. California’s Department of Public Health did not provide comment for this story by publication time.
Virginia, Massachusetts, and New Mexico confirmed last week that they will be bowing out, and Maryland added itself to the shutting-down list today. Wisconsin deactivated its app on April 3. “We were very clear up-front that it comes down when we no longer need it,” says Jeff Stover, chief of staff for the Virginia Department of Health, the first state agency in the US to launch exposure notifications. “Doing what we said we are going to do, it’s going to instill a little bit more public trust.”
Google and Apple, which said in a 2020 FAQ that they would disable the system regionally when “it is no longer needed,” so far aren’t pulling the plug on their end. Apple spokesperson Zaina Khachadourian and Google spokesperson Christa Muldoon say the companies plan to keep supporting state exposure-tracking apps that are updated to keep working after the federal shutdown.
At the height of the pandemic, millions of people in the US activated exposure notifications, as Apple and Google call them. The system arrived as a way to make loosening of strict lockdown measures safer, enabling people to be around one another without massively accelerating the spread of the coronavirus. Making Bluetooth signals the foundation of the system was inspired in part by US high schoolers’ prototype for automating contact tracing for Ebola in rural Africa.
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Public health authorities insist that exposure notifications have been a success, preventing infections by prompting people to isolate or test, and demonstrating the potential for public health apps. Critics say too few Americans turned on exposure notifications to make them truly useful. Concerns about whether anonymity would be preserved deterred some people from switching alerts on, and states struggled with limited marketing budgets to fight back. Measures such as vaccinations, face masks, and rapid tests became bigger contributors to people feeling comfortable about leaving the home.
Overall, 47 countries and 29 US states and territories have used Apple and Google’s exposure-notification technology at some point. Of the 20 US states and territories that still offered exposure notifications last week, six, including Arizona and Virginia, had brought on engineers to develop custom apps to tap the Bluetooth technology that Apple and Google added to devices with software updates early in the pandemic. The remainder had relied on a generic, free app from the two companies that will stop working when the servers go offline next month.States reliant on the free system, such as California, would have to start from scratch and maintain their own servers to preserve exposure notifications after the May 11 cutoff. “There was discussion among some states, but I don’t think that’s going anywhere,” Virginia’s Stover says.
The two national servers scheduled for shutdown are operated by the Association of Public Health Laboratories, or APHL, a group that serves as a liaison between local and federal health agencies. Emergency funds from the Centers for Disease Control have supported the servers since they went online in August 2020. But President Biden announced in January of this year that he would let the declaration of a national public health emergency—and the funding that comes with it—expire on May 11. (This month he also terminated a separate emergency declaration for Covid.)
One of APHL’s servers acts as a sort of nationwide clearinghouse for the Bluetooth data that records phones in proximity, enabling users to travel to any participating state and still get Covid exposure alerts. The other server helps verify that a particular user tested positive before anonymously notifying their close contacts, although a few states established their own setups for this function. In a message from APHL to partners that was re-posted on Twitter in February, the group’s CEO wrote that it would coordinate with Apple and Google to support a “graceful turn down process” ahead of May 11.
States giving up on exposure notifications are able to send mobile push notifications to users informing them that the system is being shut down, and that users can delete their state app or turn off the service in their smartphone settings, depending on how it is set up on their devices.
Death knells for Covid exposure notifications have already been blasted out in other countries. Australia, Belgium, and Canada dropped their apps last year. Singapore, an influential early proponent of exposure notifications, announced in February that users can delete the app, which had been mandatory for a time, but added that it would be maintained and kept in app stores in case of a Covid resurgence.
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The UK’s National Health Service is shutting down its own exposure-notifications system on April 27. “The number of people actively using the NHS COVID-19 app has steadily reduced since July 2021,” the agency said on its website last month. The volume of positive test results entered into the app, and notifications sent out, dropped after the UK reduced access to government-funded testing last year.
Researchers at the Universities of Oxford and Warwick estimated that the NHS app prevented about 9,600 deaths and 1 million infections during its first year of operation. But the exact efficacy is difficult to calculate. The anonymity built into the system and the need to make assumptions about how people would have behaved had they not received an alert make any estimates rough.
Massachusetts Department of Public Health spokesperson Ann Scales says its MassNotify system was activated on about 3.2 million phones in the state of 7 million people, with an estimated 1.5 million users currently active. Since June 2021, over 88,700 MassNotify users alerted a total of about 1.8 million fellow users about potential exposure, Scales says.
Several states and countries spent hundreds of thousands to millions of dollars to develop custom exposure-tracking apps. The race to build them also galvanized many startups, some of which have more recently shifted their apps into a broader array of health or even unrelated services as Covid-19 infection rates fell. When Apple and Google introduced the free, generic technology in September 2020, it brought many more governments on board.
But most of the apps struggled with a number of issues that ultimately contributed to low adoption, according to the US Government Accountability Office, which oversees purchasing and provides guidance to lawmakers. Its report on state Covid apps, released in September 2021, found that people were left skeptical by the possibility of inaccurate alerts due to technical limitations in measuring distance, a lack of independent privacy and security audits, and delays in issuing alerts, as states couldn’t keep pace with verifying test results.
While there have been bugs and frustrations, there has not yet been a privacy scandal tied to the Bluetooth system, and errant notifications have not appeared to be a widespread problem. “There are a lot of caveats, but we did a good job and won over a lot more people than we lost,” says Virginia’s Stover, who valued the one exposure alert he received, which came last year and led him to seek testing that came back negative.
Apple and Google aren’t letting on what they’ll do to the guts of the exposure system that they pushed into smartphones. Will exposure notifications technology be pulled from devices in future updates or sit dormant, awaiting the next big crisis? Company spokespeople declined to say.
Some government officials do not want the conversation to end. Stover says Covid apps—Virginia’s was called COVIDWISE and drew about 3 million downloads in a state of 9 million people—have made him excited about the possibility of launching a mutlifaceted state public health app one day. It could provide exposure notifications during flu season or help parents track immunization schedules for children. “We learned too much,” Stover says, “to just put it in the closet.”
Updated 04/17/2023, 6:55 pm ET: This story was updated to add Maryland's plans to discontinue its exposure notification app.