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The UK’s National Health Service (NHS) is finalising the release of a contact tracing app designed to slow the rate of infection for COVID-19. The tracing app, developed by the digital unit NHSx, is based on the evidence provided by a team of Oxford epidemiologists, mathematical modellers and ethicists in the Nuffield Department of Medicine, based at the Big Data Institute.

The COVID-19 tracing app will be released as part of a broader test, track and trace strategy devised to help stop the spread of COVID-19. The app uses simple Bluetooth technology that records close proximity contacts between two smartphone users. If a user then develops symptoms, they can choose to anonymously alert the contacts with whom they have been in close proximity.

Professor Christophe Fraser, co-lead on the mobile tracing app programme at Oxford’s Nuffield Department of Medicine explains, “Our studies identified very early on that a large proportion of infections happen before people develop any symptoms. Once we understand how much silent transmission is happening, we realise a rapid and widespread solution is needed to capture and notify close contacts of a suspected case. We now have a large team of manual contact tracers undergoing training, but we know from our experience early on in the epidemic that manual contact tracing alone wasn’t fast enough to stay on top of the virus. Our evidence suggests that the app could provide the most effective early warning system, as soon as someone first develops symptoms. Success will rely on close integration of the app into a coordinated test and trace programme. The app is being fine-tuned ready for launch to ensure if can reduce the greatest number of onward infections and help to save many lives.”

The contact tracing app will ask users to self-diagnose symptoms and then, if required, request a test to confirm. The app will anonymously notify contacts using an intelligent risk-based system designed by the team at Oxford, informed by the biology of the virus and the physics of how respiratory viruses spread. The algorithm assesses the likelihood that a person may be infected and infectious to others by considering a number of parameters including the frequency, timing and distance of the Bluetooth ‘handshake’. This risk-scoring approach provides an additional layer of protection to avoid unnecessary alerts, reduces the need for widespread quarantining and can help to identify trends of inconsistent or malicious use.

Professor Fraser continues, “We developed a model city of 1 million inhabitants, our latest simulation results suggest that app users will cause one third fewer onward infections in their community than non-app users. The results demonstrate that even at moderate levels of uptake users will benefit from a protective effect from family, colleagues and community using the app. We’ve seen really encouraging results on the Isle of Wight, with more than 50% of the population downloading the app; we’re confident that many communities are willing to support local and national efforts to save lives and protect the NHS by receiving or sharing anonymous alerts if they are at risk of infection.”

Dr David Bonsall, co-lead on the programme at Oxford’s Nuffield Department of Medicine and clinician at Oxford’s John Radcliffe Hospital explains, “For contact tracing to work, be it manual or digital, it needs to find people before they infect others. Digital contact tracing is not a silver bullet, but it has an important speed advantage that could help control the epidemic. For example, if an infected individual uses the app to send instant notifications to friends and colleagues also using the app, then between them they could prevent a local outbreak. Tracing and testing as quickly as possible will enable us to release people who are not infected and allow many of us to keep moving responsibly.”

The team of Oxford scientists argue the UK’s choice of a centralised app architecture will significantly improve the NHS’s ability to refine, improve and evaluate the app’s configuration; they suggest it will ensure the app can rapidly and effectively guide the right people to self-isolate whilst enabling most people to start returning to normal life.

Dr Robert Hinch, senior researcher on the mobile app project team at Oxford’s Big Data Institute, adds, “The app designed by the NHS will also help to identify and respond to localised outbreaks, it will result in fewer widespread lockdowns and enable life-saving NHS resources to be targeted where they are most needed.”

The Oxford team’s latest paper entitled, Ethics of instantaneous contact tracing using mobile phone apps in the control of the COVID-19 pandemic, published in The Journal of Medical Ethics, suggests the app could fulfill several ethical imperatives including the significant reduction in the number of COVID-19 cases and deaths. The app should enable users to continue their lives in an informed, safe, and socially responsible way. The authors explain the ethical importance of each individual being given a choice to install and use the app, and the value of empowering users to help control the epidemic, regain personal autonomy, return to work and make important decisions about how they start going about their daily lives.

Lead author of this ethics paper, Professor Michael Parker from Oxford’s Welcome Centre for Ethics and Humanities highlights the ethical importance of saving lives and reducing suffering during a global epidemic, “It is vital to ensure there are appropriate safeguards around the storage and use of data, but we must also consider the number of lives that might be saved from sharing relatively small amounts of appropriately depersonalised data, and the benefits of using such data to better prepare for the next pandemic and protect future generations. Personal choice is also ethically important. Many people, perhaps most, will value the opportunity to download an app with the potential to inform them how they can best contribute to protecting the NHS and reducing the human, social and economic suffering we have all experienced.”

Professor Parker concludes, “Building on the scientific model we published, the NHS has developed an app founded on epidemiological principles designed to save as many lives as possible, reduce the devastating impact of lockdown, and help us prevent another surge in cases. We argue that the success of the app in addressing the pandemic depends crucially on well-founded and sustainable public trust and confidence.  We have shared a number of ethical requirements for the appropriate use of the app since the apps conceptualisation, including the importance of independent oversight, privacy protections, high standards of data security, and consent.”