About this tracker

  • The NHS Test and Trace (NHSTT) system aims to control the spread of COVID-19 in England by ensuring that people can be tested when necessary, and by identifying close contacts of people who have tested positive (positive cases) and asking them to self-isolate.
  • The government’s Scientific Advisory Group for Emergencies (SAGE) has recommended that at least 80% of close contacts of positive cases must be reached for the system to be effective.  
  • In this tracker, we monitor and reflect on the performance of NHS Test and Trace, analysing the latest statistics on the number of positive cases reached and the number of contacts who were asked to isolate each week since the launch of NHSTT on 28 May 2020.
  • The tracker will be updated every 2 weeks. It was last updated on 19 November 2020 with additional data covering 5–11 November 2020.

Key points: 5–11 November

  • After two weeks of improvements, NHS Test and Trace performance has stalled whilst the number of people testing positive continues to rise.
  • Nearly 157,000 cases were transferred to the system in the most recent week, up from 142,000 the week before. However, the number of contacts identified remained largely the same at around 314,000. This is because the number of contacts per case has fallen over the past few weeks, possibly a result of increased social restrictions.
  • The percentage of contacts reached by NHS Test and Trace remains just 61%, a figure that’s barely changed for the past five weeks. This means that optimistically, 51% of the contacts of known cases are being reached (based on 84.9% of cases reached and 60.5% of contacts), far lower than what is needed to meaningfully limit disease spread.
  • Finally, the data provided still don’t show the contribution of local contact tracing systems to overall NHS Test and Trace performance, and the updated local authority data highlight huge variation in the proportion of cases and contacts reached in different parts the country – the percentage of cases reached ranges between 71% and 93%, and for contacts it ranges between 49% and 68%.
  • Local contact tracing systems are being implemented across the country to work with NHS Test and Trace and reach cases the national team are unable to contact. As we move into winter, they are likely to play an important role in improving overall NHS Test and Trace performance, alongside ensuring that people who are identified as cases and contacts have adequate financial and practical support whilst isolating.

Long read

NHS Test and Trace: the journey so far

About 16 mins to read

Long read

Launched at the end of May, NHS Test and Trace is not yet the ‘world-beating’ contact tracing...

Key points from previous weeks

  • Between 22–28 October, nearly 140,000 cases were handled by NHS Test and Trace, 16% more than the previous week and a nine-fold increase since the start of September. Despite this rapid increase, the system has consistently been able to reach over 80% of cases, however the percentage of contacts reached stubbornly remains at 60%.
     
  • This means that whilst 115,000 cases and 196,000 contacts were reached and advised to isolate, over 24,000 cases and 131,000 contacts weren’t. And the system is still far from achieving the 80% of contacts needed for the effective system recommended by the government’s Scientific Advisory Group for Emergencies (SAGE).
     
  • Encouragingly, the time between taking a test and getting results is falling and the percentage of cases being contacted within 24 hours has increased to 67%. This is a significant improvement on just 44% the week before. The widespread use of rapid test kits may help to further improve the time it takes to receive test results, but this is still being piloted and not yet available across the country.  

  • The number of people testing positive keeps rising, up 12% from last week to over 100,000 this week for the first time. And of the 96,521 that were passed to NHSTT, call handlers were still able to reach 81% of cases.
     
  • But things are taking longer. The median length of time taken for people to receive test results for in-person tests (regional, local and mobile test sites) has jumped from 28 hours last week to 45 hours this week. The proportion of non-complex cases reached within 24 hours of being passed to NHSTT has fallen to 54% compared with 77% at the beginning of September (with implications for local contact tracing teams – see last week’s entry below). And the proportion of their contacts reached within 24 hours of the case being transferred to NHSTT is now just 32% compared with 52% back in early September.
     
  • And while the proportion of cases being reached remains high, the proportion of contacts reached has fallen for the fourth week in a row to 60% of all contacts. But rather than this being due to worsening call handler performance, it’s mainly a result of non-complex contacts (where there is a lower success rate of being reached compared with complex contacts) making up a higher proportion of all contacts this week compared to the week before.
     
  • The average number of contacts per case for the 76,096 non-complex cases transferred to NHSTT is the same as last week, but for the 1,796 complex cases, the average number of contacts has fallen from 29 per case three weeks ago to just seven per case this week. This may just be due to chance, but it also may represent a combination of better social distancing, more limited social mixing, and appropriate use of personal protective equipment (PPE) in care settings.

  • On 2 October, the national system identified an error in how pillar 2 cases are transferred to contact tracing. This meant that 15,841 cases (from 25 September to 2 October) that hadn’t previously been sent through to NHS Test and Trace (NHSTT) were transferred in bulk on 3 October. Therefore, this week’s data include 11,000 cases transferred to NHSTT that would have ordinarily been dealt with the previous week.
     
  • This week the percentage of cases reached increased from 75% to 77%, and the percentage of cases providing details of contacts also rose from 83% to 85%, its highest since NHSTT began. This shows a slight improvement but doesn’t tell the whole story.
     
  • There were still 20,000 cases that weren’t contacted by NHSTT, and of those cases providing details of contacts, the average number of contacts per case has dropped significantly. This could be due to several factors including people not mixing as much due to increased social restrictions. Correspondingly, the percentage of all contacts that are from the same household as the case has been rising for four weeks in a row, from 57% in the first week of September to 66% in the most recent week.
     
  • Local contact tracing systems are being set up across the country - around half of local authorities now have one in place. Generally, these local systems follow up local cases that the national team hasn’t reached within the first 24 hours of being transferred to NHSTT. Their workload in recent weeks has not only been affected by rising case numbers, but also by significant delays in how long the national team takes to reach cases. The percentage of cases reached within 24 hours has fallen for four successive weeks, and now stands at just 56% of all cases transferred, down from 77% in the first week of September.
     
  • The percentage of contacts of non-complex cases that NHSTT reaches is also falling, and is now just 58% compared with 64% two weeks ago. This may partly be down to difficulties in reaching contacts from cases whose transfer to NHSTT was delayed, but when factoring in evidence that as little as 11% of contacts may actually comply with isolation rules, the implications for containing transmission are significant. These issues are exacerbated by how long it’s now taking for NHSTT to reach contacts and advise them to self-isolate. The proportion of close contacts reached within 24 hours of either the contact or the case first being identified is now at an all-time low of 61% and 39% respectively.

Useful definitions

  • Cases are people who have had a positive antigen swab test.
  • Cases managed by Public Health England local health protection teams (HPTs) are those linked to outbreaks, for example someone who works at or recently visited a hospital or care home. These cases were previously known as complex cases. All other cases are not managed by local HPTs and were previously known as non-complex cases.
  • Close contacts are defined as anyone who a case has had face-to-face contact with (within 1 metre), spent more than 15 minutes within 2 metres of, travelled with in a car, or sat close to on a plane.

Further reading

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NHS Test and Trace: the journey so far

About 16 mins to read

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