Coronavirus statistical update: teething problems for test and trace

The app which the government was trialling on the Isle of Wight has had to be abandoned – a setback for the test and trace system which lies at the heart of the government’s strategy for containing the spread of coronavirus while progressively relaxing restrictions and getting the economy and schools functioning again. Meanwhile the alert level has been reduced. Nick Terdre reports.

The NHS app has been dropped after it proved ineffective at recognising other phones, as the government had been warned – it identified reportedly only 4% of Apple iPhones and 75% of Google android phones.

The government has now reluctantly switched to an app incorporating Apple and Google technology, as used by other European countries, which recognises other phones but is still undergoing development. One key capability it presently lacks is accurately and reliably measuring the distance to other phones – a key attribute if phone owners at risk of becoming infected due to their proximity to persons found to be infected are to be identified for track and trace purposes.

With data available for the first two weeks of test and trace, it is possible to evaluate how well the system is working. And unfortunately it is not hard to see why Dido Harding, who heads the system and said in the early days that it was working well, admitted on 18 June that there was a ‘gaping hole’ as it had failed to contact more than a quarter of infected people.

‘Experimental’ statistics from the Department for Health and Social Care show this to be the case. In the second week of test and trace operations, 4-10 June, 5,949 people who tested positive for coronavirus had their case transferred to the contact tracing system. Of these, 4,366 people (73.4%) were contacted and asked to provide details of recent close contacts – less than three quarters. Attempts to contact a further 1,435 were unsuccessful while for the remaining 148 no contact details were available – a total of 1,583.

Through those who were reached, a further 44,895 people were identified as close contacts. Of these 40,690 people (90.6%) were successfully contacted and asked to self-isolate. It was not possible to contact the other 4,205, who may be infected, and spreading infection,  without knowing it.

If the 4,366 infected people who were contacted led to the identification of 44,895 close contacts, using the same proportion, the 1,583 who were not contacted might have led to the identification of another 16,277 or so close contacts, who may also be infected and spreading infection while continuing to circulate freely.

True proportion

Meanwhile questions have been raised about the true proportion of the infected population who are reported to the test and trace system. According to the Office for National Statistics, in late May/early June, the first week the system was operating, there were an estimated 33,000 or so infected people in England. In that week 8,096 infected cases were referred to test and trace.

Although the figure of 33,000 will include people who were already identified as infected prior to this period, it would seem that the test and trace system is working with far less, possibly well under half, of the population it should be working with.

The 8,096 infected people referred to track and trace in the first week is also only a relatively modest proportion of the number of new cases reported at the government’s daily briefings, which in the same period totalled 15,430. While the latter figure is for the UK as a while, the overwhelming majority would be in England.

In the second week, when 5,949 cases were referred to test and trace, the number of new UK cases reported at the daily briefings was 9,933.

In sum there are several grounds for concluding that there is a substantial shortfall in the number of cases being tracked and contact-traced.

ESCC funding

Meanwhile East Sussex County Council has been allocated £2,534,832 to support its work, and that of the county’s lower tier local authorities, in preparing plans for combatting local outbreaks of coronoavirus.

“We welcome the funding from central Government to support a local plan which determines how we deal with any future outbreaks in East Sussex and determines the role of local authorities and organisations in preventing and controlling the spread of Covid-19,” ESCC told HOT.

“We are currently developing our Outbreak Control Plan in partnership with the NHS, Public Health England, District and Borough Councils, the police and Healthwatch. We await further guidance from Government before we discuss how to make best use of this funding.”

Prevalence of infection in decline

Meanwhile a survey by the Office for National Statistics shows that the proportion of the population living in the community in England – not in institutional settings such as hospitals and care homes – which is infected is falling. From 0.33% on 26 April it dropped to 0.07% on 13 June.

This is good news not just due to the decline in numbers but also because this is the population aimed at by the test and trace system. Fewer infected cases should make the system’s task easier.

However the ONS warns that there are signs that the decline is flattening out. It hit 0.08% on 30 May and 0.07% on 5 June and has not fallen since.

Alert level falls to 3

There are those who argue that relaxing the lockdown should not have begun while the country was still on alert level 4 – the definition of which is that “a Covid-19 epidemic is in general circulation; transmission is high or rising exponentially.” Yesterday saw a switch to level 3: “a Covid-19 epidemic is in general circulation.”

Certainly it is some time since parameters such as new cases or deaths were rising exponentially, and transmission is clearly not judged to be high. At the same time, however, the R value , or rate of transmission, remains stuck at 0.7-09.

On Friday, for the first time, regional R estimates were released. These show the Midlands at 0.8-1, London and the North-West at 0.7-1, the South-East, East of England and North-East and Yorkshire at 0.7-09 and the South-West at 0.6-0.9.

On 19 June DHSC reported 173 deaths confirmed with a positive test. ONS estimates of excess deaths over the number that would normally be expected continue to run higher than the ministry’s figures; its latest ONS estimate, on 5 June, was 51,804, against 40,261 for DHSC on the same date.

Brazil has now overtaken the UK as the country with the second highest number of deaths behind the US. Today the World Health Organisation reported 47,748 deaths for Brazil, where numbers are still rising fast, against 42,461 for the UK. The toll in the US has reached 118,205.

 

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