Latest T&T data: wk 22-28 April

- no big shifts in numbers tested by LFDs/PCR, and ongoing fall in +ve cases

- but some interesting changes in contact tracing: fewer contacts reached and it's taking longer, and the reasons aren't straightforward🧵…
While the number of cases transferred to contact tracing fell by 12% to 10,793, the number of close contacts identified rose by 2% to 49,151.

For the first time since the start of August, avg contacts per case was >5.
And of those contacts, the percentage reached has dropped wk on wk for the past 5 weeks, from 90% to 84%.
BUT - this is almost all explained by change in the proportion of close contacts that are from the same household. Which has been plummeting.

There's no change in % of HH and non-HH contacts reached, consistently around 96% and 75% respectively in each setting.
More contacts overall and a greater proportion from a different HH reflects greater social mixing.

And the consequences are also seen in some of the timeliness data.

Percentage of contacts reached within 24 hrs has fallen a touch from 98.2% to 96.% in recent weeks.
But the percent contacts reached from the time the case is transferred to T&T has really deteriorated. Falling from 70% to 46% reached within 24hrs over the last 5 weeks.
The same is also seen in the end-to-end time.

Most recent data show 61% of contacts reached within 3 days of case taking a test, compared with >80% at the end of March.
Finally on this, test turnaround time is relatively stable.
- only small fall in % of contacts reached within 24hrs of being identified
- stable test turnaround times
- but significantly worsening end to end times

it follows that problems lie mainly with time to reach cases rather than contacts.
The report explains that longer time is partially due to international arrivals.

This may make sense if it takes time to identify/log all passengers on a flight.

But once known, contacting should be straightforward as details should be collected following int'l travel
Which in turn, should mean that if international arrivals are partially driving increased end to end time and increasing proportion of non-household contacts seen in the data,
then given contact details of travellers are made available for follow up...
the percentage of non-HH contacts reached should be increasing. Which it isn't.

Unless it's offset by difficulties in reaching non-household contacts of non-travel related cases

Either way, it's not straightforward to unpick and is still unlikely to explain all the changes seen
I'm sure I've missed some explainers/detail here. But bottom line is that while much is still going fairly well, it's all taking a bit longer.

And this all has implications for containing viral spread, particularly around imported cases and potential variants of concern. /end

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More from @ADMBriggs

6 May
This week's PHE surveillance report, 26th April - 2nd May

- despite easing of social restrictions & schools returning after Easter hols, case numbers still going down among all ages.
- still regional/local variation
- and ++concerns around variants.🧵…
Still some big differences by region - particularly looking at younger adults in Yorkshire and Humber.

Case rates in Y&H are 42/100,000, more than 3 times the rates in the SW at just 12/100,000.
This is even more apparent when looking at data by local authority.
Read 14 tweets
22 Apr
Updated our T&T performance tracker, covers 8-14th April.

Key points
- lots of changes to LFD use, with differences across the country
- despite falling cases, end-to-end journey time from symptoms to reaching contacts increasing

Detail in 🧵…
After a dip over the Easter bank holiday w/e, number of people tested increased by 15% to 4.4m

although this is still some way off the peak of 6.2m four weeks earlier
The changes have been mainly due to variations in use of rapid lateral flow devices (LFDs).

These have been rolled out by the government for people without symptoms over recent months and are now available to everyone in England.
Read 18 tweets
22 Apr
PHE's surveillance report for 12th to 18th April now out. 🧵

Second week of school holidays for most, but some schools will have gone back.

- case numbers down & vaccination up
- persistent inequalities by geography, ethnicity, & deprivation…
Case rates & positivity continue to fall across the age groups with no clear sign of pre-Easter rise in school-age cases leading to more infection in older ages.

Highest in 10-19y/o (42 per 100,000) and lowest among 70-79y/o at just 7.2/100,000.

A pattern matched by ONS survey
Case rates also falling across all the regions, with slightly higher rates in Yorkshire and Humber (45 cases per 100,000 compared with just 14/100,000 in the SW).

Again not dissimilar to ONS and good to see case rates come down (next ONS update due tomorrow)
Read 18 tweets
19 Apr
Having now worked it's way through the @Telegraph system: with @louisemarsha11, our take on the plans for replacing Public Health England. 🧵

tl,dr: we need a more, not less, joined up system if we're serious about health & inequalities

No £-wall🔓…
PHE is being split into the UK Health Security Agency (UKHSA which also includes Test&Trace) - focusing on external threats like pandemics

and the Office for Health Promotion - focusing on health improvement and inequalities, such as obesity and tobacco.…
As we wrote at the time, it's a risky business reorganising public health in the middle of a pandemic.…
Read 25 tweets
8 Apr
This week's Test & Trace data - for 25th to 31st March (around the last week of school before holidays)

- LFD tests down
- big variations in LFD use across the country
- and increase contacts per case.…
The number of people tested week on week has fallen for the past two weeks, down to 4.8m from a high of 6.2m.
The fall is due to reductions in LFD use - down 23% to 5.5m.
Read 25 tweets
8 Apr
This week's @PHE_uk COVID surveillance report, 29th March to 4th April (incl. start of the school hols). 🧵

⬇️ case rates, partly from fewer 10-19y/o LFDs with no clear sign yet of schools leading to ⬆️cases in older ages

+ important variation by region…
Further drop in cases in the most recent week following a bit of a flattening off in previous weeks - with some of this due to school holidays and fewer LFD tests.

Worth noting that for March, both REACT and ONS surveys suggest that case rates are generally static.
Big drop in LFD use, which is mainly due to a drop in test use by secondary schools (see T&T data).

The drop off has accelerated with the school holidays, but the move from testing in school to at home may have contributed over the past few weeks.
Read 19 tweets

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