Chart of the week: Covid-19 test and trace programme is still a leaky system

Each week we present analysis of data in chart form to illustrate some key issues and invite discussion. With the delayed NHS Covid contact tracing app slated to launch later this week, Billy Palmer takes another look at the pipeline of the test and trace programme, and finds a system still weighed down by inefficiencies and uncertainties throughout the process.

Chart of the week

Published: 22/09/2020

The NHS Test and Trace programme forms a central part of the government’s coronavirus recovery strategy. More than three months after the programme commenced in England in May, we’ve pieced together the data to look at the extent to which the issues we previously identified have been resolved.

We’ve found a system that is still far from water-tight, with leakages all the way along the pipeline – from the numbers of people referred to the Test and Trace programme right through to those being told to self-isolate.

  • It is likely that large numbers of infected people are being missed. Although 15,526 people were ‘transferred’ to NHS Test and Trace in the week to 9 September, during that period a higher number – 18,371 – tested positive. And the estimated number of new infections in the community was somewhere in the region of 59,800 over a similar timeframe.
  • But of those transferred, around one in six (2,424) could not be contacted and 271 had no contact details.
  • Of the 12,831 infected people who were reached, around one in six again could not provide recent close contacts. And where contacts were provided, fewer than three-quarters (74%) were reached and asked to self-isolate.
  • Crucially, of those people then asked to self-isolate (12,831 positive cases and 45,653 recent close contacts in the last week), there is still no information available on how many have done so. A previous estimate from the government’s own Scientific Advisory Group for Emergencies (SAGE) suggests fewer than one in five might be fully adherent to self-isolation and quarantine.

Since its launch, the system has delivered some improvements and in this latest week has had to deal with a substantial increase in cases. However, the latest data also show people are waiting longer to receive a test result. There also remain some key unknowns, such as whether the recent close contacts provided by each infected person is comprehensive. We will have to wait and see whether the long-awaited app – due to be released on Thursday this week – helps in this regard.

Of course, it is unrealistic to expect a perfectly performing programme – other countries are struggling with contact tracing too. But it is also clear that the system continues to fall short of what is needed.


Data sources: Nuffield Trust analysis of Test and Trace data and other sources listed in the accompanying text.