It's being widely reported that 1 dose of the Astra/Oxford vaccine reduces transmission by 67%. My understanding is that this is not what the paper shows, or what the authors have claimed. I'm happy to be corrected if I've got this wrong. Short thread.…
The Astra/Oxford trial asked people enrolled to self-swab every week and send in swabs for testing. They also asked them to reach out and get tested if they had symptoms. So all tests carried out are a combination of:
1. asymptomatic testing
2. testing sought due to symptoms
When we break down efficacy by these categories, the trial reports an efficacy of 76% in preventing *disease* (or symptomatic infection) and ~16% efficacy (with a lot of uncertainty due to small numbers) for asymptomatic infection. The combined efficacy for PCR +ves is 67%
Does this mean infection or transmission is reduced by 67%. It's difficult to know. Certainly the paper is careful not to make this claim. It only talks about reduction of PCR positives by 67% with the 'potential' to reduce transmission.
The Oxford press release also doesn't say this. It speaks about reduction in positive swabs with potential impacts on transmission. The estimate for reduction in infection will depend on other factors, including the compliance with routine swabbing.

This is hard to estimate from the paper. Of course impact on transmission is even harder to know. The media coverage of this is a bit concerning to me because I've been asked several times today whether it's ok for those vaccinated to socialise now that 'transmission is reduced'.
I think the media should ensure this is correctly and cautiously reported - it should not be reported as a 76% reduction in transmission. And those who are vaccinated should continue to take precautions to protect themselves and others.

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More from @dgurdasani1

3 Feb
I believe that claims that scientists make need to stand up to scrutiny, especially in the midst of a pandemic, where scientists have an ethical duty to inform accurately. Calling out false claims is not the same as trolling & harassing someone because they disagree with you.
During the past many weeks, I've engaged with scientists when I felt they made claims that were not in line with current evidence. I usually do this by first contacting the scientist directly & discussing why evidence cited may be flawed, &/or providing direct evidence against.
In my experience, this approach has not worked. Inevitably, it has led to people claiming personal attacks, which means they don't have to engage on the evidence. So evidence-based discussions don't happen, and discussions get shut down.
Read 18 tweets
3 Feb
A thread discussing recent evidence on longer gap dosing with Astra/Oxford, Pfizer, current gaps in our understanding of impacts, as well as the possible impact of new variants on vaccine effectiveness. Thread.
First, I want to say that this although thread may highlight uncertainties & gaps in current evidence I fully advocate taking the vaccine, as this will offer protection. But I also firmly believe that discussing uncertainties in evidence & transparency around data is important.
Astra/Oxford published data yesterday, suggesting that longer gaps between the 1st and 2nd dose may be associated with higher efficacy. Vaccine efficacy between 3-12 wks after a single dose was reported to be 76% with protection being similar throughout this period.
Read 24 tweets
2 Feb
Concerning data from PHE today suggesting that sequencing shows that there are 11 cases of the UK variant (B117) identified that also have the E484K mutation (the one found in the so-called South Africa and Manaus variants). This is important and concerning for many reasons. 🧵
To recap the B117 ('UK variant') is defined by a number of mutations, including the 501Y mutation thought to be associated with increased transmissibility, which is also shared by the so-called South Africa (B1351) and Manaus (P1) variants.
In addition, both B1351 (SA) & P1 (Manaus) variants also have the E484K mutation. This mutation has been associated with a high level of escape of neutralising antibodies directed at previous variants in the laboratory, raising concerns about vaccine efficacy.
Read 24 tweets
1 Feb
I've recently come across a disinformation around evidence relating to school closures and community transmission that's been platformed prominently. This arises from flawed understanding of the data that underlies this evidence, and the methodologies used in these studies.
Let's look at the paper being cited here. This study published in Nature Human Behaviour examined >50,000 interventions (at fine scale) across >200 countries. The number of countries examined allowed examination of these in depth.…
As the authors state, the key strength of the study is that examination across so many different contexts allowed a disentanglement of interventions. The authors used four approaches, including a case-control analysis to specifically deal with this issue.
Read 13 tweets
30 Jan
These studies are heavily flawed, and are don't include any of the larger, and less biased studies that contradict this view. There are ample studies with larger sample sizes, including from the ONS, that show primary school children play an important role in transmission.
And completely misses the direct impact on children from Long COVID. 12% of primary school children have symptoms lasting > 5 wks. We need to look at this based on the breadth of evidence, and the design of these studies- which unfortunately even many scientists haven't done.
The ECDC paper is extremely flawed, and quotes largely studies from symptom based testing designs, which we know hugely underestimate the impact of children on transmission. And from periods when either community tranmission was low, or school attendance was low in many regions.
Read 8 tweets
26 Jan
On @BBCOS today discussing the tragedy of exceeding 100,000 COVID-19 deaths in the UK, and what led to this.

19:03 for a bit and then 19:23 onwards:…

Also, a few thoughts in a thread below:
The PM said during the briefing today, that the govt did the best they could. He was 'deeply sorry' for every single death.

If every single death is a tragedy, then why didn't we treat every death as preventable?

Why did we repeatedly talk about 'tolerable deaths'?
How on earth can he say he did his best, when UK policy was almost never evidence based - and the govt invited proponents of the ideology of naturally acquired herd immunity to brief him on policy- at a point in time we urgently needed to act to prevent thousands of deaths?
Read 16 tweets

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