THREAD: I know many people are thinking "but how can this new variant be scary when overall case numbers are flat?"

Here's how.

(Numbers that follow are illustrative but based on case data & sequenced proportion data from Sanger: covid19.sanger.ac.uk/downloads) 1/6
Cases of B117 ("Kent") variant have been falling every week, while cases of B.1.617.2 (1st sequenced in India) have been growing. Total cases are B117+B.1.617.2.

We've had two epidemics at once. During early days for B.1.617.2, its growth is entirely masked by fall in B117 2/6
As proportion of cases that are new variant grows, overall cases start to creep up - but not by much. Not at first.

In this example, it's an 11% increase week ending 22nd May. 3/6
As soon as new variant becomes dominant, cases start increasing much more quickly - *assuming* it keeps growing at the same rate.

According to Saturday's PHE tech report & Sanger data, we've probably just reached the tipping point in England between B.1.617.2 & B.1.1.7. 4/6
The growth in cases is then quite rapid. Who knows if this will happen here - but if it does it should be obvious. And we should see it in next couple of weeks.

B.1.617.2 has showed a few signs of slowing growth past few days - but even so we should still see something. 5/6
At the moment, total cases are almost perfectly in line with this illustration. Cases in England rose 15% in week ending 23rd May.

If we *don't* see increases over next 2 weeks, I think it's fair to be less worried about B.1.617.2. 6/6

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More from @chrischirp

26 May
SHORT THREAD on Scotland & Covid:

Cases in Scotland have been going up since early May. Image
Cases are rising most steeply and most notably in children and young adults, but have now started rising in older groups as well (but, presumably much reduced by vaccination impact).

chart from @TravellingTabby travellingtabby.com/scotland-coron… Image
Many argue that it's ok cos the link between cases & hospitalisations has been broken cos of vax.

Regardless that this ignores long covid or potential for further mutation, this is NOT TRUE.

The link has been weakened but NOT broken.

Scottish admissions have started to rise. Image
Read 6 tweets
25 May
The latest Wellcome Sanger data on local spread of B.1.617.2 (variant of concern 1st seq in India) dropped yesterday. It tries to get at community cases by removing cases from travellers & surge testing.

All regions going up - inc NE & Yorks now.

Flattest in London & SW. Image
The SW has v few cases and most B.1.617.2 cases are travellers so it's not very useful data.

For London, we need to understand why that is flatterning more than everywhere else.

Also - local "lockdowns" a bit late if aim is to stop spread to other areas!
Oh and here is the overall England proportion of sequenced cases that are B.1.617.2, B.1.1.7 and other variants up to 15th May.
Also from Sanger institute.

Now almost 50% (consistent with Saturday's PHE report). Image
Read 4 tweets
24 May
SHORT THREAD ON SCHOOLS:
As we open up, schools are becoming the biggest places where large groups of unvaccinated people mix.
This makes them more vulnerable to outbreaks if local cases increase.
But data on what is happening in schools is sparse.
Firstly, twice weekly lateral flow device tests (LFDs) - the government's main mitigation in secondary schools now that they've removed masks - are not really being done.

There should be about 8 million LFDs a week in secondary schools. But we are only seeing 2 million.
Numbers picked up a bit after Easter holidays but are now back to where they were in mid April & at ~25% of expected tests (and that's not counting school staff)

Regardless of how effective an intervention it is, this is the government's main strategy. And it's not being done.
Read 11 tweets
23 May
LONG THREAD on B.1.617.2 & latest PHE data covering:

1) latest tech report on B.1.617.2 (aka "India" variant)
2) vaccine efficacy against B.1.617.2
3) consequences for roadmap
4) avoidability... or not.
2. So first off, PHE tech report released late last night.

Can detect B.1.617.2 by direct sequencing OR by using "S gene" in a PCR test (now 99% of these are B.1.617).

BOTH these methods now estimate that as of 15th May B.1.617.2 was on cusp of being dominant English variant.
3. There is no evidence that B.1.617.2 causes more severe illness than B.1.1.7 (aka "Kent" variant). This is good news but data still quite sparse.
Read 36 tweets
23 May
I disagree. Let's look at the last 3 crucial weeks:

6th May: PHE very concerned about B.1.617.2 & about to make a VoC. Report delayed because of local elections, pubished 7 May. PHE bounced into announcement by Guardian & Channel 4 coverage.

theguardian.com/world/2021/may… 1/5
13th May: Report was ready on Thursday afternoon with a page on schools data (seen by Observer) - report published hours later in the evening with just the schools page removed.
Observer has seen evidence this removal was at Num 10 request.
theguardian.com/world/2021/may… 2/5
20th May: PHE told journalists report would be released on Thursday (when it was due). it was not. Then Friday lunchtime - it was not. Then Friday sometime. It was not.

Finally released Sat night - no press release (unlike vax report released at same time). No school data. 3/5
Read 6 tweets
22 May
THREAD on vax study for B.1.617.2 (new "Indian" variant):

@jburnmurdoch broke a story from PHE data with the first real world analysis of AZ & Pfizer vaccine efficacy against B.1.617.2.

I am less convinced this is great news than some. Here's why.
ft.com/content/a70d42… 1/16
The study estimates that both vaccines are 33% at preventing symptomatic B.1.617.2 disease after 1 dose (vs 51% against B117 ("Kent")) and 81% effective after 2 doses (vs 87% for B117).

Too little data on preventing severe disease to say much but v likely to be better. 2/16
So the vaccines do mostly work against B.1.617.2 - especially after 2 doses. That's good news - but not surprising.

We already had evidence from a care home outbreak, & Bolton hospital. Early lab studies suggested less escape than B.1351 "S Africa"
blogs.bmj.com/bmj/2021/05/18… 3/16
Read 16 tweets

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