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Successful COVID-19 exposure notification system shuts down in most states

Photo of an iPhone showing a notification that says, "Exposure Notifications Off."

By Melanie Padgett Powers

As the COVID-19 Public Health Emergency expired on May 11, 2023, the COVID-19 Exposure Notifications System (ENS) in the majority of states also shut down. For the past three years, APHL has played a critical role in the US ENS.

The COVID-19 ENS made it possible for users to receive smartphone alerts when they — or more accurately, their phone — had been in the vicinity of someone who soon after reported a positive COVID-19 test through the ENS.

APHL, in collaboration with Google, Apple and Microsoft, and with program funding and guidance from partners at the Centers for Disease Control and Prevention, has provided support for the ENS by hosting national servers since August 2020.

“The availability of these servers eliminated a significant burden for state public health authorities and enabled exposure notifications to occur across state lines, despite each state having a unique solution,” explained Emma Sudduth, APHL consultant and program manager for the national server operations.

At one point, 28 states were using the ENS and relying on the servers hosted by APHL. Over time, as pandemic restrictions loosened and vaccine uptake increased, some states’ public health authorities discontinued their exposure notification solutions. Most of the remaining states shut down ENS on May 11 as Apple, Google and APHL discontinued their support for key components of the system.

The ENS saved countless lives across the country, as people were alerted to exposures, allowing them to get tested quickly and take precautions to reduce the ongoing spread of COVID-19. Research in Washington state in June 2021 showed that the state’s exposure notifications tool, known as WA Notify, had saved an estimated 30–120 lives and likely prevented about 6,000 COVID-19 cases during the first four months of its use.

By 2023, WA Notify had approximately 235,000 participants share a positive test result, which generated more than 2.5 million anonymous exposure notifications.

“We’re tremendously proud of what WA Notify was able to accomplish in a relatively short amount of time, and eager to find ways to utilize this life-saving technology again in the future,” said Bryant Thomas Karras, MD, chief medical informatics officer at Washington State Department of Health. “Much of WA Notify’s success can be attributed to innovative collaboration among public, private and academic partners,” which included APHL, Apple, Google, Microsoft and the University of Washington.

Unprecedented private-public health partnership

It became clear early on in the pandemic that most states did not have the time, funding or capacity to create their own ENS. Even if they did, it would have resulted in several different types of exposure notifications tools across the country.

To solve this problem, Google and Apple partnered to create a turnkey solution called Exposure Notifications Express (ENX). ENX made it easier for public health agencies to launch a state ENS by eliminating the need to build their own tool. These private technology companies looked to APHL, as a trusted public health partner, to host the servers.

“APHL has a long history of supporting states in data exchange and the hosting of solutions,” said Scott Becker, APHL CEO. “Our participation in the ENS gave the US public health community a capable and accountable partner for hosting key components of this groundbreaking technology.”

APHL stepped up to provide the necessary national key server, which holds the ENS data for the entire country. With APHL taking responsibility for storing and securing the data, states did not have to host and maintain their own servers. The Bluetooth-enabled notifications and the digital language known as “exposure notification keys” protected privacy.

Furthermore, a national centralized server allowed exposure notifications to work between users who had tools published by different states, ensuring notification regardless of state boundaries.

“The national infrastructure supported by APHL was essential to the deployment and maintenance of exposure notification systems,” Karras said. “By securely hosting the [national servers] APHL removed the burden on individual public health authorities to build and host their own servers, and importantly, enabled communication, i.e., interoperability, between exposure notification tools deployed in the U.S. Interoperability ensured that individuals using the systems could seamlessly notify others when traveling across states.”

Lessons for the future

Throughout the nearly three years of ENS, lessons were learned and applied to improve the system over time. This resulted in more states providing an exposure notification solution and more users in those states adopting it, which led to higher levels of notifications.

The knowledge and experience gained with the use of the ENS means that, in the future, public health won’t have to start at baseline to build a system from scratch. In addition, the ability to learn from different states about their experiences with ENS could be leveraged for future public health solutions.

The private-public health partnership — with Google and Apple working together with APHL, along with the public health community and state health departments — was the first of its kind and shows the value of such measures. The ENS saved lives, prevented cases and slowed disease spread. The public health community will continue to explore how such innovations can be used in the future to improve public health.

“Washington State Department of Health recognizes the great value of public-private-academic partnerships and collaboration with other states to develop interoperable systems,” Karras said. “This collaboration allowed us to accomplish something that would not have been possible without working together. We are committed to strengthening these partnerships that have made exposure notification systems so successful.”

At APHL, Sudduth said, “The collaboration between private technology companies and public health in this endeavor made a far stronger solution. Learning from this experience and growing these established relationships will strengthen public health.”

Learn more about the Exposure Notification System and APHL’s role:


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