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Source: United Kingdom – Executive Government & Departments

The government have released the latest figures from the COVID-19 Test and Trace programme. 

Prof James Naismith FRS FRSE FMedSci, Director of the Rosalind Franklin Institute, and University of Oxford, said:

“It is important that the government continues to publish these statistics.

“Unfortunately they are not encouraging. 51, 475 people tested positive suggesting that the virus is continuing to spread, with a doubling time of around 10 to 14 days.

“The number of people being newly tested in pillar 2 each week has levelled off at around 400, 000, the growth in positives is mainly in pillar 2, with around 45, 000 total in this period.

“Particularly concerning was that only 34, 494 were transferred to tracing. 11,000 of the gap resulted from last week’s IT error. Even so, a gap of around 6,000 is disappointing. The 11, 000 will appear next week, so this means next week’s figures will need careful analysis. If a significant portion of positive cases are not entering tracing in a timely manner, this will undermine the value of the system.

“Of those transferred to tracing, around 3/4 were reached and of them 84 % provided details, roughly 63 % success rate overall for those transferred. The lower this overall number, the less effective the system will be in reducing viral spread.

“The average time taken from a positive case to ask for contacts has increased, there is notable fall off as the system has come under pressure. The longer the delay the less effective the system.

“2 of 3 close contacts being identified share the same household. As the reports says, one can assume the household members know of the positive case and will be aware they should isolate even without a call. The added value will mostly come from the non-household contacts who isolate because of the call. We do not know if this 2/3 contact ratio is accurate? If it’s not, then we are missing close contacts and this decreases the effectiveness of the system.

“Crucially we have very little insight into how effective isolation is for both positive cases and their contacts. Failure to isolate will further undermine the system.

“I would urge SAGE to estimate what the reduction in the spread of the virus the track and trace system is delivering. Has it reduced spread by more than 50 %, 25 to 50 %, 10 to 25 % or less than 10 %?

“As case numbers increase, the time, energy and cost of scaling up this system will continue to grow. We have enough data for some indication of their value to be made.”


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

“The Test and Trace disclaimer reads “Data collected for NHS Test and Trace is primarily for operational purposes and was not designed to track the spread of the virus.” Why were data collected for Test and Trace not designed and available to track the spread of the virus? England’s disclaimer contrasts with Scotland’s use of intelligence from Test and Protect in the Evidence statement that backed-up the announcements yesterday on additional restrictions in Scotland, see  and click on “evidence”.

“In addition, it is now 11 weeks since the statement by the Royal Statistical Society’s COVID-19 Taskforce on how to use statistical methods to gather intelligence robustly about symptomatic cases, asymptomatic infections and how much adherence to self-isolation there is by those told to do so by the Test and Trace system. England’s apparent rejection of responsibility to learn about transmission within high-risk households, which may contain individuals who are 70+ years or those with relevant co-morbidities, is frankly astonishing in public health and disease control terms.

“Remember that many other countries have opted to isolate the first individual to get symptoms and test positive from a household to reduce the risk of transmission to others in the household . . .  We should at least learn how high the risks are when UK has instead advocated for the entire household to isolate together but try to “self-isolate” within the home (not easy!)

“Failing the above, can we please at least start reporting publicly how many of our daily-reported new positive cases were and were not already in quarantine on the date when they were tested?”


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 constructive recommendations on 23 July about how Test and Trace could learn efficiently.”

None others received. 

MIL OSI United Kingdom