Apple and Google announced on September 1 that they will deploy digital contact-tracing tools on behalf of state and other public health authorities. The tools could help slow the spread of COVID-19 by informing users if they come into contact with someone who tests positive for the virus.

States have so far been expected to develop their own applications that work with the tech giants’ recently-launched contact-tracing infrastructure. But Apple and Google will now deploy contact-tracing tools using parameters provided by state health agencies. Google will use the information to create apps for Android phones, while Apple will implement contact-tracing for iOS devices that isn’t reliant on apps. The new initiative, Exposure Notifications Express, will let public health authorities submit parameters for contact tracing to Apple and Google. Those parameters include an agency’s standards for what constitutes a coronavirus exposure, what actions users are instructed to take if exposed, and visual elements including logos. Google will then create an app for Android phones available through the Android App Store, while Apple will set up “app-less” notifications for iOS.

Digital contact tracing is a supplement to traditional manual contact tracing. In manual tracing, which has been used to fight pandemics for decades, infected individuals are interviewed by health workers about those whom they have been in contact with recently. Those at-risk individuals are then notified to self-isolate and seek testing, to prevent them from infecting others. Digital contact-tracing tools do similar tracking automatically, using cell phones’ Bluetooth and GPS systems to anonymously monitor users’ possible exposure.

Contact-tracing apps developed by or for state health authorities will all interact using a decentralized, privacy-preserving data system jointly developed by Apple and Google. The new app development process will not affect those privacy features, which rely on phones communicating with one another at short range, and sending only minimal, anonymous data to a central server.

Taking the technical burden off of states should help increase adoption of digital contact-tracing apps. Apple and Google launched a new data system in May to run the apps, but only six U.S. states have developed their own app since then, while 25 more are in talks with the tech giants. Representatives for Apple and Google said on September 1 that a lack of technical staff has been one of the major barriers to the deployment of contact-tracing apps by remaining states.

Despite efforts to preserve privacy, there is substantial worry that Americans will be hesitant to use the apps. Some have said that low adoption could make them ineffective, based on an Oxford study that found 60% adoption of the apps would be sufficient to control a pandemic.

But that threshold referred to the necessary adoption rate of digital contact tracing in the absence of other measures. Oxford professor Christophe Fraser, one of the researchers behind that study, has since emphasized that as little as 15% of a population using digital contact-tracing apps could reduce COVID-19 infections by 15% and deaths by 11%.