Have digested the latest excellent technical briefing from @PHE_uk on variants and Delta (the variant formerly known as B.1.617.2) in particular. as ever, all findings are context dependent and should be interpreted with care, but this is serious and deserves a wide audience 1/?
First, read all about it yourself (don't take my word for it!). Briefing here assets.publishing.service.gov.uk/government/upl… and Risk Assessment assets.publishing.service.gov.uk/government/upl… 2/?
This is from the risk assessment. Yes there is a lot of red. There is now very good evidence of increased transmissibility (will come back to that) compared with Alpha/B.1.1.7 (already quite transmissible). This is important. There is also... 3/?
Clear evidence of reduced vaccine effectiveness vs Delta. It is *not* clear how much of the apparent increase in transmission is due to this, and it is not clear what breakthrough cases look like right now. My own expectation is that they are milder than they would have been 4/n
(that's also a finding in this recently dropped preprint. I've not had time to fully assess it though, to figure out what it is based on so hoping someone else will!) medrxiv.org/content/10.110… 5/?
somewhat counterintuitively, more transmissible is MUCH worse than mild immune escape going forward, so unraveling this will be important especially for places with little current immunity and low vaccination 6/?
The data on vaccine effectiveness in the report is not broken down by vaccine unfortunately, but the assessment specifically states this. I can see several sources of bias and wouldn't call either way on this now. But nailing down the answer to this is going to be important 7/?
It is also possible that the reduced effectiveness might be consistent with much milder infection in vaccinees. But we don't know right now. Quite a lot of younger people in the UK, and indeed people in general in some places, are yet to receive any shot! 8/?
Next thing. Early data, but consistent between England and Scotland, suggests Delta is more likely to lead to hospitalization than Alpha. This is less secure than the other findings and as yet does not seem to have been broken down by vaccine status 9/?
This is going to take time to unfold and people should be patient. It takes time to resolve infections and see what happens in the course of disease, and the situation is changing quickly. We're not even 28 days from a lot of these diagnoses 10/?
(for those really paying attention, for the English data a stratified Cox proportional hazard regression was used that *did* adjust for vaccine status among many other things, but I think more work is still needed on this) 11/?
Reinfections don't seem to have been noticeable so far at least #OptimismSpa. This is good news, but the cohorts being followed for reinfection are far smaller than the total cohorts receiving vaccines, and so I am unsure how detectable a difference would be. Time will tell 12/?
This figure highlights schools as a common exposure in contact tracing. This should be interpreted in terms of local context I can't provide, but I believe that infection control in high schools in particular has been patchy and recently relaxed. Please read the next tweet 13/n
Note that before saying whether or not schools should be closed, you need to think about how you can mitigate transmission within them, and the consequences of transmission from kids to adults who may be vaccinated. Again, the nature of breakthrough disease matters a lot 14/?
👏🏼To all involved in producing this. The significance for the UK depends on how well the current vaccines protect (I'd guess quite well against severe illness) but elsewhere we need to be vaccinating more 15/?
I'd note too that I will revisit this as data comes in for the UK! The accelerated delivery of 2nd doses is certainly wise at the moment. let's not see how many times Delta can double before it runs out of people to infect 16/n
Finally this is awesome news, but there are *far* more than 80m people needing vaccines in the world. Once your community is highly vaccinated, please remember others that have not been as fortunate washingtontimes.com/news/2021/jun/… 17/end
Not least by specific vaccine received, controlling for age etc

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More from @BillHanage

4 Jun
So growth rate and R number in the UK now over 1. Unsurprisingly given that Delta variant now dominant. A short thread on the next few weeks there, which will be (sorry) big on uncertainty gov.uk/guidance/the-r… 1/n
That's quite a large increase. The caveat of course is that it is from a *very* low base indeed. And cases will not necessarily translate into severe illness, especially in vaccinated people 2/n
Unfortunately these too are up, from a low baseline. This should be treated with caution because when numbers are this low they can be impacted by unusual events like clusters of infection in vulnerable populations - although you'd hope such folks were vaccinated 3/n
Read 9 tweets
2 Jun
I read this article this morning and it made me uneasy, I've just figured out why. Not linking deliberately although easy enough to find if you really want to 1/n
The article admits that a definitive answer on the origins of the pandemic is probably never going to be available (I agree), and then proceeds as if it were. This is silly 2/n
If there will never be a definitive answer to the question, why act like there will be? In its absence people will pick sides based on pre-existing positions rather than accepting uncertainty. And the thing is we'll be better off in the future accepting that uncertainty 3/n
Read 6 tweets
27 May
I was wondering earlier today if change was afoot in the UK due to B.1.617.2, but @jburnmurdoch's thread is better than anything I could put together. It deserves your time. I do think it misses something out however. Hospitalizations are climbing much earlier than I'd expect 1/n
First it certainly looks like B.1.617.2 has become readily established, and is sweeping in multiple different places suggesting that it is more transmissible even than B.1.1.7, itself no slouch. IMO we can't put this down to founder effects/networks 2/n
(I still don't understand why given what *looks* like high transmissibility it has an MRCA so far back, but it's clearly capable of causing outbreaks like these. That's enough to take it seriously) 3/n
Read 14 tweets
26 May
A few points about "Chicken Pox parties", and why they should never have been part of any serious discussion of pandemic management thejournal.ie/dominic-cummin… 1/n
Like Covid, chicken pox is more likely to lead to severe illness and complications the older you are when you are first exposed. In the UK in the 1990s about 25 people died every year of the infection, 80% being adults ncbi.nlm.nih.gov/pmc/articles/P… 2/n
It is generally thought that on recovery from chicken pox immunity is lifelong. As a result in the 70s and 80s some people would arrange for their kids to be infected at an age they would be at lower risk of complications. This is not a good idea 3/n infectioncontrol.tips/2015/12/18/its…
Read 8 tweets
25 May
How to start on the problems with this? Herd immunity to SARS-CoV-2 through unmitigated outbreaks comes at an abysmal cost in deaths, and chronic outcomes of infection. Ok we know that now but... 1/?
We knew that *then* theguardian.com/commentisfree/… 2/?
We knew it in the autumn too theguardian.com/commentisfree/… 3/?
Read 8 tweets
16 May
Thinking about the uncertain situation w B.1.617.2 in the UK as the country opens up, this is very good (no surprise, it's @adamhfinn answering the questions). I have a few additional points and a mild point of disagreement 1/n theguardian.com/world/2021/may…
The additional point - it's really not clear what is going on with 617.2. It has certainly been growing, but that doesn't necessarily mean it is (much) more transmissible. It may have merely had more opportunities 2/n
As more contacts and opportunities for transmission arise in the UK, we can expect them to result in more cases. Having said that of course, we need to ask why one lineage rather than another is lucky enough to take those opportunities - maybe it's more than luck 3/n
Read 11 tweets

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