First, new AY.4.2 Risk Assessment

• Transmissibility: 🟥 RED
increasing numbers against Delta, AY.4.2 has an advantage

• Severity: 🟩 GREEN
no evidence of worse outcomes for AY.4.2

• Immunity: 🟩 GREEN
lab & surveillance studies show no difference in vaccine effectiveness
Let’s break it down:

++AY.4.2 immunity data++

In 2 lab live virus neutralisation studies, AY.4.2 had modest reduction (2.3-2.8 fold) vs D614G wild-type


*No difference* compared to OG Delta

• Denmark pre-print {…}
• UK G2P Consortium
++AY.4.2 Immunity Data++

@UKHSA real-world Vaccine Effectiveness analysis
{adjusted TNCC design}

• AY.4.2 VE symptomatic infection is the same as OG Delta (AZ, Pfizer, Moderna)

• AY.4.2 VE hospitalisation is the same as OG Delta (AZ & Pfizer only)
Good news then for AY.4.2

It’s slight advantage in infectiousness means it will become the dominant strain.

However, it does not appear to differ from OG Delta in any other ways that are of concern. 🦠
But AY.4.2 is a slooow burner 🔥

Gaining 1-2% prevalence per week

• 11.2% of cases 17-23 October
• 13.0% of cases 24-30 October
• 14.7% of cases 31 Oct to 6 Nov
Finally, a less upbeat note… 😬

++ Delta+E484K ++

E484K is a spike mutation known to evade the immune system

Both neutralisation studies found significantly 4-5 fold reduced neutralisation titers for Delta+E484K

Which puts it on par with Beta (which also has E484K)
So - a Delta variant that’s good at evading the immune system 😯

How worried should we be?

Don’t lose sleep...

We’ve seen previously that E484K’s immune advantage appears to come at a cost to the virus’s fitness 🦠

Meaning E484 borked the virus
Only ~170 cases of Delta+E484K in UK. Mostly in 3 self-limiting outbreaks.

But other mutations could appear that un-bork the virus & that would be… not good 👎

{points to pretty graph of literally dozens of other spike mutations on Delta}

Definitely one to watch 🔍

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More from @kallmemeg

15 Nov
NEW: first bit of data out of @UKHSA early this Monday morning is a study on booster effectiveness, trailed by JVT in press conference

Real-world study from England shows *very* high effectiveness (>90%) against symptomatic infection vs unvaccinated

That is the headline, and it is the main driver for a rather huge policy shift to drop the threshold for boosters to age 40, in a bid to protect the NHS over the winter months.…
There are 2 other impressive conclusions from this study:

1. Comparing vaccine effectiveness of booster vs 'fully vaxxed' as the baseline. Booster ADDS 81-85% protection against symptomatic infection ON TOP of what you already had from your primary (2-dose) vaccination
Read 11 tweets
12 Nov
Right. Our rental is in the country and I need a country person to tell me WHY DO THE COWS MOO ALL NIGHT LONG AND CAN THEY NOT PLEASE🐮🥱
…and a cockerel at 5am fml
The culprits, so brazen, still mooing.

I may need a couple days to be sure they’re the same lot of cows, but I’m sure there were 3 calves with them yesterday.

Could they have separated the babies from the mummy cows? Image
Read 4 tweets
8 Nov
NEW: Household transmission of Delta vs Alpha now published 😊

Odds of household transmission 70% higher for Delta vs Alpha

{18 Mar - 7 June, 10,518 Alpha and 7,410 Delta cases}

5 Tweet 🧵…
This is an update to the analysis first in Tech Brief 15 and preprinted here; the source of the “63% more transmissible” stat:…
Why has the % increased?

The analysis was updated to:

• exclude households of 1 (who couldn’t transmit in the household)

• extended study period to June to include more Delta cases, and reflect a time with more community transmission (via travel imports)
Read 5 tweets
29 Oct

Happy Friday! NEW @UKHSA report focussing on AY.4.2

Technical Briefing 27 - AY.4.2…
NEW addition this week is Vaccine Effectiveness (VE) of AY.4.2

• No evidence that VE (infection) is lower for AY4.2 vs OG Delta after 2 doses of vaccine

• Holds true for both symptomatic and asymptomatic infection

• Adjusted for age, sex, CEV, week of test, & other factors
By vaccine type: 💉

• No change in for AstraZeneca or Moderna

• Pfizer VE aOR=1.12 (95%CI 1.0-1.16) for symptomatic infection, so a possible borderline reduction.

• But in real terms an OR=1.12 equates to a reduction in Pfizer VE from 83% to 81%.

Negligible impact.
Read 8 tweets
26 Oct
💭 on reinfections

We can only count the data we have.

Only 1 in 4 infections were tested during pandemic (est)

Many were missed in the first wave - but even now we only catch 50-70%

Even if/when we count re-infections it will be 300-400/day which will not change policy a jot
If we want to be able count reinfections accurately we need a lab record for each infection.

That means we need the whole population to test regularly & report their results.

Too ambitious? Then we need to accept the limitations.

It is what it is.

A more realistic option is modelling using population surveys either self-reported (bit dodgy) or N/S antibody sampling.

I know Zoe and ONS are undertaking these studies using their own methods.
Read 5 tweets
25 Oct
💭 on the recent decline in cases in children {eg graph by @JamesWard73}

Cases starting to fall in under-20s

My knee-jerk reaction is CONCLUDE NOTHING IT IS HALF TERM!

That the decline precedes half-term by a week could be avoidance of testing to avoid ruining holidays…

And under-20 is a huge age group.

HOWEVER, unpicking into 5 year age bands shows a similar decline in all groups, even in the long-suffering 10-14 year olds.

Biggest drop *MAY* even be in 10-14?

{but far be it for me to draw conclusion from 1 day of data…😉}

Could this decline be real? MAYBE, JUST MAYBE

Comparing @MRC_BSU modelled attack rates from now vs before school started:

{attack rate = the % of that population ever infected}

In only 2 months, half of children aged 5-14 in England were infected (estimated)

Read 10 tweets

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