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Contact Tracing and the Fight Against Covid-19: How Digital Tools Can Help

Briefing6th April 2020

Chapter 1


Contact tracing (CT) is a monitoring process that is a central public-health response to infectious-disease outbreaks. As the WHO explains,[_] it can be broken down into three basic steps: 

  1. Identifying someone who has a disease

  2. Listing all those who have come into contact with the person

  3. Monitoring and following up with those people

Such measures were put in place during the Ebola outbreak[_] in West Africa and during the Middle East respiratory syndrome (MERS)[_] coronavirus in 2015. It can be an effective tool, but there are practical, resource-based constraints (see The European Centre for Disease Prevention Control outline of resource estimations[_] needed for such processes). However, technology is now also being used, with digital and automated tracing taking place in countries around the world. This is potentially crucial to reducing the size of outbreaks. If effectively deployed, tech-assisted CT could be part of a broader strategy for loosening social-distancing and lockdown measures over the longer-term. 

Chapter 2

Key Facts
  • A London School of Hygiene & Tropical Medicine study[_] estimates that in most scenarios CT and case isolation are “enough to control a new outbreak of Covid-19 within three months.” 

  • Researchers at Oxford University’s Big Data Institute estimate that a combination of isolation and CT/quarantining could bring the virus’s reproduction number (R0) below 1 and control the epidemic, if tracing is instantaneous. 

  • During the Ebola outbreak, implementation issues were identified with paper-based systems.[_] While challenges exist, Dimagi’s mobile data collection platform in Sierra Leone highlighted that mobile health solutions can be deployed in low-connectivity and low-resource environments. 

Figure 1

contact-tracing-and-fight-against-covid-19-how-digital-tools-can-help - f3b0fcd2-5366-4197-9659-d746da846313

Chapter 3

Policy Analysis

Political leaders, technologists and society face three key challenges when implementing contract-tracing measures: 

  • Efficacy and population coverage 

  • Interoperability 

  • Data privacy (opt-in or opt-out) 

Contact tracing is integral to fighting outbreaks, but digital solutions are largely being explored for the first time. As with traditional CT measures, how these digital tools are deployed and the speed at which they are delivered is key. The resource constraints and digital capacities (such as smartphone penetration and digital literacy) of countries will also greatly vary, which will alter the solutions that they choose to adopt. Automated tracing is possible but is likely to require deep trade-offs with civil liberties. SMS- and WhatsApp-based solutions are also possible, including on an open-source basis. 

Figure 2

contact-tracing-and-fight-against-covid-19-how-digital-tools-can-help - Source:


Examples of countries taking steps on digital CT include South Korea, which is using a deep set of tracing measures, including GPS and location tracking. The South Korean government has explicitly acknowledged the intrusive nature of the tools being used, but legal changes made in the aftermath of MERS have allowed their use. These changes include amendments to the country’s Infectious Disease Control and Prevention Act, which gave the Minister of Health the “legal authority to collect private data, without a warrant, from both already confirmed and potential patients.” 

Taiwan, which has a tech-enabled civic culture,[_] has also been effective in its response and has recently announced a mobile phone-based “electronic fence” that uses location-tracking to ensure that those who are quarantined stay at home. Singapore has also developed the TraceTogether[_] app, which uses Bluetooth to track and notify people who have come into contact with those infected by the virus. It’s non-mandatory and they have set clear conditions on data usage and ensured it is time-limited, with the government making the software available to others via open source. However, the government has said that only around one in six have downloaded it since it was launched two weeks ago, which is not above the 75 per cent coverage threshold needed for effectiveness. In announcing school closures, the prime minister also highlighted the challenge of implementation at this stage, stating that for many of the recent cases, which include transmission from those returning from overseas, for nearly half they “do not know where or from whom the person caught the virus.”

In Europe and the US, partnerships have been explored with Big Tech and telcos about providing anonymised data to model and monitor movements. A broad push is also happening to develop tracing apps, with a survey conducted[_] by researchers and made available on the open platform, OSF, suggesting there is broad public support. The NHSX is leading UK efforts to develop an app that, similar to Singapore’s, would use Bluetooth to log users’ proximity and notify should people be exposed to an infected individual. This raises some definitional issues, as well as the need to minimise false positives. As the Oxford research indicates, 60 per cent of the population would also need to be signed up for it to be effective. Offering it on an opt-in basis is likely going to be necessary to gain consent, and while Health Secretary Matt Hancock has already given the legal basis for the NHS to set aside the duty of confidentiality in response to Covid-19, the government has said data[_] collected will be time-limited. The release of this app is likely to coincide with the easing of lockdown measures, at a time when R0 is below 1 and stable, and wider system capacity has been developed. However, circuit-breakers should also be put in place, so that if rebounds do occur, the system can respond and adapt immediately. 

As a result of privacy concerns, a number of other solutions are being developed outside government. Prominent among these is an MIT-developed app, Private Kit: Safe Paths,[_] which stores up to 28 days of users’ GPS location data (harder to anonymise, but researchers are exploring new cryptographic approaches[_]) and allows them to share that information with health officials if they test positive for the virus. Covid Watch, which is backed by Stanford University, CoEpi, and NextTrace[_] are all developing similar technology, while in in Germany, GeoHealth gives users the ability to choose to “donate” their location data history if they have tested positive. 

Having multiple providers within the market is likely to result in issues of interoperability, which those working on the challenges in the US have said they will solve by developing a common protocol and through being connected to the same data pool. Scaling up quickly and efficiently will be critical, so collaboration will be key. A group of researchers in Europe have also been exploring “Privacy-Preserving Proximity Tracing,”[_] offering a decentralised solution so that data is not collected on servers, nor processed even if on an anonymised basis. 

Figure 3

contact-tracing-and-fight-against-covid-19-how-digital-tools-can-help - 99f38942-9de4-437f-8e05-87877edd270e

Using smartphones to locally compute risk offers a lot of advantages for individuals, while the model that is being proposed is also interoperable and scalable. It works within existing legal frameworks, while the researchers are also proposing a mechanism of consent to share data with epidemiologists. The end result could be a protocol that can be operationalised on a country-by-country basis, although speed is of the essence. 

Some governments around the world have already taken severe measures in surveilling the population as part of contact-tracing efforts, but this is unlikely to work in many jurisdictions. Instead opt-in solutions, which are transparent, clearly communicated and which have clear safeguards, are more likely to work. Community mobilisation is also going to be essential to ensure take-up. Either way, it is clear that contact tracing is going to be an important tool in fighting the virus, easing lockdowns and then controlling any potential rebounds in future. Given the nature of Covid-19, not least its high levels of transmission, this is not going to be the only solution, but it is right that governments are now moving quickly in this space. Wider collaboration is also going to be necessary, with the adoption of technology central to it all. 

Chapter 4

  • Contact tracing will be essential to fighting further outbreaks of Covid-19, but for it to be effective, R0 needs to be low and government needs a detailed understanding of who is infected. Testing is therefore critical. 

  • Deeper digital solutions are likely to be effective, but there will be a trade-off with privacy in many cases. Decentralised solutions could be viable but need to be developed quickly. 

  • Governments will need strong community mobilisation to ensure take-up. If different technological solutions exist, interoperability and common protocols are critical.   


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