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Adam Briggs

3 Dec, 21 tweets, 12 min read

It's that time of the week.

Test and Trace performance figures for 19-25th Nov. Wk 26.

Tl,dr: some changes to how cases are managed, and overall as cases fall, the systems showing signs of improvement.

Summary in pic, detail in thread.

gov.uk/government/pub…

A 5% drop in the number of people getting tested this week (to 1.66m), but a 28% drop in cases.

Drawing conclusions about falling positivity rates over time is getting increasingly tricky as testing among asymptomatic people is rolled out. As have said previously, reporting symptomatic separately to asymptomatic would hugely help with understanding the data.

Use of LFDs still relatively low, but will rapidly increase. Reports from Liverpool suggest they found around 25% of their recent weekly cases, but this will vary by LFD uptake and disease prevalence.

Interpreting longitudinal test data and case rate data is going to get harder

There's generally a fair bit of good news this week.
Firstly, as test numbers fall, test turnaround time is generally improving

116,324 cases were transferred to T&T, and 98,784 (85% - similar to previous weeks) were successfully reached. 17,540 weren't

As with last week, 96% of cases were handled by the national T&T team, alongside local authority contact tracing teams for those cases the national team can't get through to within 24hrs.

That proportion of cases going to local teams is falling, the second bit of good news.

79% of cases reached provided details of close contacts (81% the previous week).
And so along with the falling cases, there are fewer contacts - 246,604 identified, 29% fewer than the week before.

It's also worth noting here that the number of contacts per case for those more complex cases managed by health protection teams is 2.6. The lowest ever and almost identical to 2.5 among cases handled by T&T.

The fall among these cases is really interesting (was as high as 31 contacts per case in early Sept). I would love to know more about why it's happening, but likely a combination of better COVID-secure working, lockdown, and social restrictions

The big change this week is the jump in the percentage of contacts reached. Up to a whopping 73% overall and 71% among those managed by T&T (it's never previously been more than 64% among these cases and was 59% last week).

This is because NHSTT has changed how they manage household contacts under 18. Instead of having to separately reach all contacts who are under 18 years, the parent or guardian can take responsibility.

This makes sense and ensures that households receive fewer calls.

And the change is going to be extended to adults from 27th Sept so we should expect to see a step in performance then as well.

This addresses a really important problem that's been genuinely causing problems for households. It's great to see it now addressed.

Plus, the immediate impact of this change on performance suggests the change has been welcomed by households.

Even as proportion of contacts that are same HH rises, the improvement in % of close contacts reached is entirely due to improvements in reaching household contacts.

For non-household close contacts, the percentage reached remains at 64% as it was the week before.

And of course, being able to record reaching these household contacts at the same time as phoning the case has done wonders for the overall timeliness of contact tracing.

The percentage of contacts reached within 24hrs of a case being identified has increased to 61% from 44%.

The system can still improve.
Fact remains that >17,000 cases weren’t reached by T&T, & only around 60% of the contacts of identified cases are being reached (based on 85% of cases reached, and 73% of their identified contacts), still far from the 80% level recommended by SAGE.

There's tonnes more to be done but it's encouraging to see some sensible changes that will improve how cases are managed.

And it would still be really helpful to tease out the role of local contact tracing systems in all this data.