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expert reaction to latest NHS Test & Trace stats for the week 16 to 22 July, along with a policy paper on next steps and priorities, and a campaign encouraging everyone with symptoms to get a test

The government have released the latest data from the NHS Test and Trace service as well as a policy paper on their next steps and priorities, and a campaign encouraging everyone with symptoms to get a test.


Commenting on the latest stats:

Prof Sheila Bird, Formerly Programme Leader, MRC Biostatistics Unit, University of Cambridge, said:

“Let me begin by congratulating both the laboratories and the statisticians respectively on improvement in timeliness of test-results and on de-duplication of, and improvement in, records about those tested.  Below I draw some important contrasts between weeks 1+2 versus 7+8 that this set of improvements facilitates.  But I’ll end with what’s still missing!

“What’s still missing: Test & Trace’s poor performance in reaching identified close contacts who are members of the household of a non-complex index case is extraordinary and needs explanation.  Is language a barrier or age-group (extreme youth or being very old) or illness; and why does Test & Trace not enlist the help of the index case or – as recommended by the Royal Statistical Society, (see – select a random sample of index-case households to be visited on a random day (or pair of days) during the household’s quarantine for swab-testing to be offered.  These random visits also check on adherence and would allow the reasons to be understood for T&T’s failure to reach over 40% of household members when the index case is non-complex.

“Also missing is any account of how many of the nearly 90,000 close contacts who were asked by Test & Trace to self-isolate during weeks 1+2 subsequently booked a swab-test and tested RT-PCR positive for SARS-CoV-2 during or soon after their quarantine period.  Linkage within Test & Trace’s own data must hold the answer.  Please let us, the public, know the answer.  Answers should be provided separately for the close contacts of complex cases; for identified household members of non-complex cases (reached versus not reached); and for identified external close contacts of non-complex cases (reached versus not reached). 

Some of the above suggestions and reflections may already be addressed in the policy statement released today about future plans for Test & Trace.  I do hope so.”


Commenting on the campaign:

Prof Sian Griffiths, Emeritus Professor, the Chinese University of Hong Kong, and co-chair of the Hong Kong government’s SARS inquiry, said:

“If we are to control the spread of the virus, Test and Trace needs to be working well both now lockdown is being released and as we move into the winter season when we expect to see a rise in flu cases and related hospital admissions and deaths.  Experience globally and more recently at a local level here in the UK has shown how testing in communities can identify positive cases, initiate isolation and quarantine and reduce and control the risk of spread.  The campaign highlighting the availability of tests for all those experiencing symptoms, and encouragement for people to come forward, is to be welcomed.  Also to be welcomed is the increasing recognition that successful results rely not only on a national testing framework which produces timely results but on joint working with local authority teams, led by Directors of Public Health and supported by data ,who are able to respond to the circumstances of their local communities.  This has been and will continue to be particularly important in communities with hard to reach vulnerable groups, including some BAME communities.”


Commenting on the policy paper:

Prof Jose Vazquez-Boland, Chair of Infectious Diseases, Edinburgh Medical School, University of Edinburgh, said:

“The new policy plans in Test and Trace are an important step in the right direction.

“They recognise the key importance of further improving the testing capacity, accessibility and turnaround times, expanding the coverage of asymptomatics, and improving local outbreak control.

“However, emphasis is still placed on testing suspected cases, i.e. people with symptoms, the tip of the iceberg.  The target for asymptomatics, an average of 150,000 tests a day by September, should be far more ambitious.

“A plan is definitely needed for rapid systematic identification of pre-clinical and subclinical infections, which are the recognised major source of community transmission.

“Only the regular screening of everyone in the population for asymptomatic transmitters can contain the circulation of the virus and achieve covid-19 eradication without having to re-impose indiscriminate lockdown measures.”



Latest stats:

Policy paper on next steps, ‘Developing NHS Test and Trace: business plan’:



All our previous output on this subject can be seen at this weblink:


Declared interests

Prof Sheila Bird: “SMB is a member of the Royal Statistical Society’s COVID-19 Taskforce which issued recommendations last week on how use of statistical methods – linkage and random sampling – can remedy gaps in Test & Trace.”

None others received.

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