One of the digital technologies highlighted in Budd et al. (2020) that I find particularly significant is the use of Bluetooth-enabled COVID-19 contact-tracing applications. While the article discusses a variety of approaches, I will focus on the joint Google–Apple framework, which was rolled out in April and May 2020.

COVID-19 spreads primarily through close contact over a sustained period. To detect such interactions without compromising individual privacy, Bluetooth Low Energy (BLE) technology was applied. The system works as follows: when two smartphones come within close range (approximately one to two meters), they exchange anonymous identification keys. These keys act like digital “tokens” of interaction, containing no personal details or location data, thereby preserving user privacy.

If an individual later tests positive for COVID-19, their device holds a record of the anonymized keys from previous close contacts. With the user’s consent, these keys can be uploaded, enabling Apple and Google’s system to notify the corresponding contacts that they may have been exposed and should consider testing or self-isolation. Importantly, the keys are randomly generated and cannot be traced back to a specific person or device. You can read details here

This technology was crucial because it enabled rapid, large-scale, and automated contact tracing, minimizing reliance on traditional manual methods, which are often slow and dependent on human memory. In densely populated or highly mobile settings, the framework offered a powerful tool to break transmission chains and support public health teams. Although its effectiveness depended on widespread adoption and public trust, Bluetooth-based contact tracing marked an important advancement in the application of digital technologies for pandemic response.