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The government have released the latest NHS Test and Trace statistics for England between the 23rd and 29th July 2020.
Prof Sheila Bird, Formerly Programme Leader, MRC Biostatistics Unit, University of Cambridge, said:
“Last week, I drew some important contrasts between weeks 1+2 versus 7+8 and ended with what’s still missing. I’ve added week 9 to my previous table.
“The percentage positive of those testing via Pillar 2 (which we worry about) has increased from 1.4% (se 0.02%) in weeks 7+8 to 1.7% (se 0.03%) in week 9; the proportion of positives transferred into Test & Trace dropped back to 93% in week 9; so that those reached by T&T & who provided contacts were 59% only of all positives in week 9, down from 65% in weeks 7+8. On average, only 2.8 contacts were reached per positive case in week 9, down from an average of 3.4 in weeks 7+8.
“In week 9, Test and Trace still reached a lower percentage (57%) of identified close contacts in the household of the symptomatic index case than of identified external close contacts (67%).
“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 needed explanation. Explanation awaited still.
“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 https://rss.org.uk/RSS/media/File-library/Policy/RSS-COVID-19-Task-Force-Statement-on-TTI-final.pdf – 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 still 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.
“Prime Minister, any world-beating Test & Trace system should inform us, the public, how many tested positive during or soon after their quarantine period who belonged to T&T’s two high-risk groups:
1. member of the household of symptomatic index case.
2. identified external close contact of a symptomatic case.
“Any world-beating Test & Trace system should also be designed to learn about asymptomatic infections in those two high-risk groups; and be able to document adherence to quarantine.
“The Royal Statistical Society made three recommendations on how Test & Trace can remedy its most serious epidemiological gaps.”
Prof Eivor Oborn, Professor of Health Care Management, Warwick Business School, University of Warwick, said:
“A most notable statistic is the slow increase in positive cases for COVID-19. This trend seems to be consistently trending upward, even though the overall numbers being tested are not that different.
“This means the virus is slowly spreading into the population. Thus we need the test and trace system working as well as possible.
“Though the system has been operating for just over two months, the percentage of positive cases being contacted through contact tracing system has remained stubbornly around 80% since mid-June.
“There is also a slight decline in being able to reach and isolate the contacts of those who test positive. In this sense the system for testing and tracing does not seem to be improving.
“In a number of ways it has reached a near steady state, such as turn around times for the testing (24 hours) and bringing the new positive cases into the tracing system. At the same time there seems to be a slight decrease in being able to identify close contacts, perhaps a sign that people are less willing to comply with bringing their contacts into self isolation, or taking precautions less seriously.
“Since our overall virus incidence is increasing in the general population, these are important numbers to try and improve.
“It would also be important to have more statistics on how many of the self-isolating close contacts actually develop into positive cases. This would help inform the public how successful the whole isolating process is and may encourage more public members to participate voluntarily in the system, if they can see that there are tangible benefits to public health.
“To elaborate, we know roughly 70-74 % of the close contacts given (from those testing positive) are aware they need to self-isolate because they are high risk for infection.
“How many of these actually go on to test positive? It would also be helpful to have an indication of how many of the people asked to self isolate are actually doing so. We do not have data presented regarding this, and whether there is a way to help facilitate the isolation, for example with online deliveries, child care or work related support. This could also help inform the contact tracers on how best to use their time and ensure efficiency in the system.”
Dr Joshua Moon, research fellow in the Science Policy Research Unit (SPRU) at the University of Sussex Business School, said:
“Cases are going up faster than testing – this is not a good sign.
“The data shows 4966 positive cases, 4642 transferred to contact tracing (93.4%), of which 79.4% provided contacts, of which 72.4% were asked to isolate. This means that of all contacts of the 4966 positive cases, approximately 53.7% were contacted and asked to self-isolate. This is also not a great sign if we’re serious about keeping the virus under control in the UK.
“Over the nine weeks of NHS T&T activity, the percentage of non-household contacts has been increasing, indicating that the changes are likely to be as a result of the Government’s decision to relax lockdown measures.”
Prof Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases, University of Nottingham, said:
“One persistent problem is that 1 in 5 cases, who should be at home and self-isolating, fail to be contacted by the contact tracers despite multiple attempts. These people have arranged a test and been informed of a positive result and expect to be contacted. It would be useful to have more information on these people as to why they are not participating in control measures.
“Not being able to trace contacts is understandable but the cases could help in letting their contacts know.
“This is a public health crisis and the public MUST play their part in it’s control. Without the co-operation of cases controlling COVID-19 will be particularly difficult.”
NHS Test and Trace statistics (England): 23 July to 29 July 2020
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
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