Contact Tracing for Covid-19 – A digital inoculation against future pandemics


Coronavirus disease 2019 (Covid-19) outbreaks emerged in the United States and European countries in February 2020. Urgent action was needed as experts estimated that 30-70% of people in these Western countries could become infected – a frightening projection at a time when the death rate from Covid-19 was estimated to be considerably higher than we know it today. In March 2020, Michael Ryan, executive director of the Health Emergencies Program at the World Health Organization (WHO), implored countries to act, noting that when it comes to responding to outbreaks, “speed wins. on perfection” but “the biggest mistake is not movement.” At the time, the only tools to contain Covid-19 were social distancing, testing, isolating cases and contact tracing.

Contact tracing is a crucial public health practice that has been part of outbreak responses for centuries. From bubonic plague, to smallpox and tuberculosis, to HIV, the fate of public health has hinged on our ability to identify people who have been in contact with infected people. In the case of Covid-19, however, the short time between the onset of symptoms in the infector and those infected and the propensity of the virus for asymptomatic transmission have posed challenges for contact tracing. Recall bias, inability to identify unknown contacts of the infected person, and shortage of trained contact tracers were additional challenges. There was an urgent need to increase the scale and speed of contact tracing to identify everyone who had been exposed to Covid-19.

Twenty-first century digital technology had the potential to enable this escalation. Modeling studies have suggested that if digital contact tracing apps were combined with other mitigation measures, Covid-19 outbreaks could be slowed and theoretically even ended.1 Lessons can be learned from the deployment of digital technologies to increase contact tracing during this pandemic.

The most basic measures of the effectiveness of a pandemic response are the number of cases and deaths. By these measures, South Korea’s response during its first wave of Covid-19 was very successful. Having experienced Middle East Respiratory Syndrome (MERS) in 2015, the South Korean people and their political leaders understood the need for early recognition of the pandemic threat and a corresponding vigorous response. They have successfully integrated a rapidly scaled diagnostic capability and contact tracing system with effective isolation and quarantine measures.

A key component of South Korea’s contact tracing system was digital contact tracing technology. Legislative changes in South Korea resulting from the MERS outbreak gave health authorities a legal basis for using geolocation data for contact tracing early in their outbreak. Global Positioning System (GPS) data from mobile phones was used to create a centralized database of the movements of people with Covid-19 that was accessible online. The Corona 100m app used this data to warn users when they were near a location visited by an infected person. This intervention undermined the privacy, data protection and civil liberties of those infected, but it aimed to disrupt the chains of transmission to protect the most vulnerable members of society.

In most Western countries, no such effort to improve contact tracing using automation was implemented early in the outbreak. Without prior experience in responding to outbreaks in this way, many leaders and citizens have found it inconceivable that privacy and data protection rights could be ceded to health protection. Yet the fact that many people in Western countries already allow geolocation data to be collected by other apps that offer little personal benefit suggests that resistance to doing so for health protection, albeit well-intentioned , may have been misguided.2

Automation using geolocation tracking has allowed teams of epidemiological investigators in South Korea to trace not only contacts, but also the context in which the contact occurred up to 14 days before the outbreak. symptoms or diagnosis. This information allowed them to better understand the contexts in which SARS-CoV-2 transmission was occurring and to implement more targeted health protection measures in response. In contrast, traditional contact tracing systems in most Western countries had the ability to identify and notify only people who had come into contact with an infected person within 48 hours before the onset of symptoms or diagnosis. . This numerical limitation may have contributed to the first wave of Covid-19 in Western countries which overtook the epidemic in South Korea. By the end of its first epidemic wave in April 2020, South Korea had reported 10,423 infections and just 204 deaths – a remarkable achievement considering the population size of just over 50 million. In contrast, European countries recorded more than 2.1 million cases and 180,000 deaths by the end of their first wave in June.

Digital contact tracing is not a perfect intervention, given the risks to privacy, personal data, and false positive or false negative characterization of contact status. However, as in a Swiss cheese model, imperfect interventions can work together to curb outbreaks. South Korea’s deployment of digital technology to increase contact tracing was an example of speed exceeding perfection, while Europe made the biggest mistake described by the WHO’s Ryan: not budging. Having learned from this experience, Europeans might be much more willing to share location data for contact tracing in health emergencies.3 It should help combat the next pandemic that the balance between preserving privacy and preserving life has shifted during this pandemic.

As the first epidemic wave has ended and the looming threat of further loss of life has subsided, geolocation-based digital contact tracing systems and their interference with privacy and data protection rights have become less acceptable. They became the subject of intense scrutiny in countries that used them, including South Korea, as well as Norway and Israel. In a pandemic that had the potential to last several years, many Western countries recognized the need for reliable, transparent and privacy-preserving digital contact tracing technologies acceptable to Western populations.

A selection of digital contact tracing systems in the United States and Europe

Following the lead of TraceTogether, Singapore’s Bluetooth Low Energy (BLE) digital contact tracing app, Germany, Ireland and the UK, among others, have set out to develop their own systems, which have been adopted to varying degrees by the target populations (see chart).4 Western countries have tended to favor a decentralized and privacy-preserving protocol for contact tracing, which means that instead of being sent to central government servers, the collected data remains on the user’s device, are encrypted and are automatically deleted after 14 days.4 By the end of 2020, there were at least 65 BLE-enabled digital contact tracing systems worldwide, including 26 in the United States.4

Although it was never believed that these systems alone would end Covid-19 outbreaks,1 evidence is emerging that they have been beneficial in identifying a higher number of contacts per case than traditional contact tracing, increasing the number of people with Covid-19 who entered quarantine, shortening the quarantine time of 1-2 days and possibly prevent large numbers of infections through the downstream effects of increased contact tracing.5

However, challenges remain. The integration of digital contact tracing technologies with existing test and trace systems appears to be an important determinant of their usefulness.5 Most importantly, digital contact tracing technologies need to be made accessible, especially to people with limited access to smartphone technology, people with limited knowledge of digital health, speakers of languages ​​other than the primary language of a country and migrant communities. Increasing accessibility is important not only to maximize adoption, but also to ensure that all members of society can benefit equally from digital advances in contact tracing. If these challenges can be overcome, Western countries will have acquired a reliable, privacy-friendly and accessible tool to use in the next pandemic to improve contact tracing capacity and control the spread of the disease until the end. elimination.


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