Tom Lees

Contact tracing may be more of a placebo than a cure

Contact tracing may be more of a placebo than a cure
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We have been told by the Government that an effective test, track and trace programme is the key to ‘controlling’ Covid-19, allowing us to further unlock the country and take the economy out of its induced coma. The effectiveness of contact tracing depends on wide ranging factors including how many people have the virus but don’t show symptoms, the accuracy and speed of testing, levels of surveillance, the number of people that come into contact with an infected person and how many people comply with requests to self-isolate. Unfortunately for the Government the odds are not in their favour with Covid-19.

This week the Office for National statistics and the University of Oxford released their third set of findings from their Covid-19 Infection Survey. Over a two-week period they performed 18,913 tests within 8,799 households. They found that around 80 per cent of people who tested positive for the virus did not have symptoms when tested, and that the number of people currently infected in England is at least 62,000. Although those in the study – with or without symptoms – were tested regularly, generally people who show no symptoms will not get tested and there is no contact tracing.

A paper written by Prof Matt Keeling of the University of Warwick found that without social-distancing the average person comes into close-contact with 59 people, of which 36 are known to them. This means that the number of people that need tracing becomes extremely large, extremely quickly.

Meanwhile, after ten weeks of lockdown, some people are understandably getting tired of following the government’s guidance and have remembered that being alive is not the same as living. As the height of summer approaches what proportion of people will be willing to fully shut themselves away for two weeks if they have come into contact with an infected person?

The Royal Society recently released modelling that looked at the possible impact of test, track and trace in the UK. As with all models, their results should be taken with a pinch of salt, but they suggested the impact of test and trace could be as low as a five per cent reduction in infections.

Test and trace may not even have had such a large impact in countries like South Korea. A recent paper from Imperial College and the World Health Organisation found that contact tracing of infected individuals was only a minor aspect of South Korea’s relative success. The country advised strong – but voluntary – social distancing measures, cases were isolated quickly and mass testing was used in high-risk locations like hospitals and care homes.

But perhaps reducing the spread of Covid-19 isn’t really the true purpose of the UK’s scheme.

The ‘stay home, protect the NHS, save lives’, message was so effective at inducing a sense of personal danger, guilt and fear that it is now a challenge to get people to feel safe enough to go to hospital when they need urgent treatment or to send their children back to school.

It is well-known that humans are often bad at judging risk and how likely things are to happen to them. This ‘weakness’ can sometimes be a strength. It can give entrepreneurs the confidence to set up a new business which will likely go bust or motivate academics trying to push the limits of human understanding, who will ultimately spend decades making an incremental contribution to human knowledge at best.

But when it comes to easing lockdown, it is a weakness. Every untimely death is tragic, but last year more people under 30 died from accidental poisoning or in car crashes than have died from Covid-19. For primary school children there were nearly twice as many deaths from seasonal flu or choking on food and the same number of children died from chickenpox.

So rather than being an effective mechanism to reduce the spread of infection, the main benefits of test, track and trace might be a well-timed placebo. Something that has little or no effect but gives people at minimal risk the sense of safety they need to leave the house and provides the government something reassuring to discuss in its daily briefings.

On that basis we should all wholeheartedly support the Government’s efforts to get track and trace fully up and running as soon as possible.

Written byTom Lees

Tom Lees is a theoretical physicist, policy expert and managing director of consultancy firm Bradshaw Advisory

Topics in this articleSociety