Contact-tracing success rate drops

Data shows declines in the proportion of both confirmed cases and their contacts being reached by tracers

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There has been a marked drop in the success rate of the government Test and Trace scheme in contacting both confirmed coronavirus cases and their close contacts.

The latest release of weekly data, covering the period from 11 to 17 June, shows that tracers were unable to reach three in ten – 29.7% – of the 6,923 people transferred to the programme’s systems that week, all of whom had tested positive for coronavirus.

Some 25.9% of these people could not be reached despite tracers’ efforts, while a further 3.8% had not provided any contact details.

During the prior week, the overall failure-to-contact rate stood at 24.8%, comprised of 22.3% that were not reached, and 2.5% that provided no means to do so.

The drop in the rate of successful attempts to reach coronavirus sufferers was reflected in the cumulative number of close contacts they provided – which saw a sharp week-on-week drop.


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During the Test and Trace scheme’s first two weeks in operation, respective totals of 52,440 and 45,840 people who had been in close contact with a confirmed coronavirus case were referred to tracers. This equates to an average of 8.9 and 10.2 people for each confirmed case that was successfully contacted. 

In each of the first two weeks, more than 90% of these contacts was successfully reached and asked to self-isolate.

In the third week, data shows that just 30,286 close contacts were identified and referred on to tracers. 

As well as a steep drop in volume, this represents a marked decline in the number of contacts per person, equating to 6.2 for every confirmed case reached by tracers.

And almost one of five of the contacts provided could not be reached, with the success rate plummeting to 81.7%.

The number of cases referred to the programme during 11-17 June was almost 1,000 higher than in the previous week.

Although the same data set shows that the total number of positive cases reported during the week dropped slightly, from 6,498 to 6,129.

The manual Test and Trace programme is, for the foreseeable future, set to remain the only means through which to track the contacts of people to have tested positive for coronavirus. Last week the government scrapped its multimillion-pound contact-tracing app after three months of work, having discovered it did not work on iPhones.

A new program, to be based on a system developed by Apple and Google, is in the works, but the government has declined to put a launch date on the technology.

Sam Trendall

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