A Brief History of Exposure Notification During the COVID-19 Pandemic in the United States, 2020-2021.

The swift global spread of COVID-19 prompted public health authorities to explore digital technologies to aid in contact tracing for infection control. Exposure notification, a mobile device-based technology that notifies individuals of potential exposure to COVID-19 without requiring personally identifiable information, has been broadly favored because of its relative ease of use, scalability, and protection of personal privacy. Although several exposure notification protocols were developed, a partnership between Google and Apple led to the development of the most widely implemented exposure notification protocol in the world, including in the United States.