Devan Sinha Profile picture
Aug 9, 2021 7 tweets 3 min read Read on X
80% [78,82] of England's Total population have now been vaccinated or infected

Wall of immunity:

10% Infected only
19% Both infxn+vax
51% Vaccinated 1or2 doses

Usual caveats: time lag after vax, not 100% protective, assumes random vaxing probability of previously infected etc
Remaining 11.5m unexposed/unvaxxed susceptible population is heavily skewed to younger age groups.

80% under 25yo
47% in school age kids 5-14yo

Outbreaks and cases will expectedly be concentrated in these groups now and increasingly <15 after current vax roll out plan completed
Quick check of the model against ONS serosurvey and PHE blood donor antibody surveillance, in 16yo+:

Model 95.8% (up to 8 August)
ONS 93.6% (12 - 19 July)
PHE 96.2% (28 June - 23 July)

Looks okay.
Expecting blood donors to be slightly more likely to be vaxxed (engaging with health services) and higher exposure/socially engaged.

3 weeks since ONS Ab data more than made up for by additional infections and vaxxing.
Overall the wall looks solid.

PHE analysis suggests 96% vaccine effectiveness against severe disease/hospitalisation against Delta and even 80% after just 1 dose.

Though *much less preferable* immunity after infection appears comparable.
Still ~25k cases/day in 🏴󠁧󠁢󠁥󠁮󠁧󠁿, demonstrating the v high transmissibility of Delta and practically unreachable 'herd immunity threshold'

Despite infections & 'waves' the vax have drastically cut the link w/ hospitalisation so much so it's no longer a systemic risk
via @VictimOfMaths
Can't stress benefits of vax enough!

They protect you and those close to you

And your immunity protects those with weaker immune systems

They protect NHS capacity so we can treat other non covid patients too

They boost freedom by making restrictions and lockdowns unnecessary.

• • •

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More from @DevanSinha

Jan 9, 2022
How many total COVID-19 deaths in the UK?:

▪️ 173,248
mentions on death certificates to 24th Dec'21

▪️ 150,154
within 28 days of positive test reported by 9th Jan'22

▪️ 119,600
age standardised excess deaths from Continuous Mortality Investigation (CMI) to 24th Dec'21

1/
1. Mentions on death cert: filled by physicians who knew the patient w/access to medical history. But includes primary cause (1a) and contributing factor or co-existing. So likely overestimate.

Proportion of 1 or 'due to' covid cause has varied over time 80-90% (ONS).

2/
2. Within 28 days of +ve test: includes incidental in period after test and where C19 may contribute but not 1o CoD (NB every hosp adms tested) = overestimate.

However, when test capacity lacking eg 1st wave spring 2020 this will lead to underestimate. (CMI chart for E&W).

3/
Read 5 tweets
Dec 16, 2021
Can this Kaplan-Meier curve apply to countries as a whole?

Thought experiment on survivorship bias in South Africa and question of Omicron 'mildness' (as we wait for better data - UKHSA case control/retrospective matched studies in 2-3 weeks)...

1/
Firstly, we need to recognise that the attack rate in RSA is very very high. Modelling from excess deaths, even if adjusting for a higher low income country IFR would place AR at over 85% and closer to 100%.

278k excess deaths = 0.5% of a demographically young population

2/
Ab serosurveys likewise showed 32-63% positivity in Jan'21 across RSA provinces before Beta wave finished or Delta wave arrived.

Projecting forward for further waves and accounting for Ab wane below limit of detection also places AR >95%.

pubmed.ncbi.nlm.nih.gov/33594353/

3/
Read 11 tweets
Dec 3, 2021
COV-BOOST RCT

3rd dose immunogenicity v AZ or PF/BNT 2dose primary course

▪️2883 randomised w/ multiple cntrl groups
▪️7 different vax boosters + some 1/2 doses
▪️1/2 age >70
▪️>84 days from 2nd dose PF and >70d for AZ til boost

For boost after 2xAZ 👇

thelancet.com/action/showPdf…
▪️For boosters UK chose after 2xAZ:
~25x fold higher Anti-spike IgG w/ PF
~30x fold higher w/ Moderna

▪️PBMC also higher ~2-4x

▪️Some age response effect, but not meeting statistical significance

separated by 1o course; some persistence of difference in anti-spike IgG and PBMC
▪️For boost after 2xPF:
~ 8x fold higher Anti-spike IgG w/ PF
~ 12x fold higher w/ Moderna

▪️PBMC also higher ~3-4x
Read 4 tweets
Dec 1, 2021
On point 1. Glad JCVI exist and appraise vaccine/immunology data.

Booster trial effectiveness is based on 6 month gap (may not be same with shorter gap) and immunogenicity studies show longer the gap between dose2 and 3 stronger the immune response.

But Omicron appears to be..
A significant evasion concern vs 2 dose symptom VE. An emergency situation that wasn't known until 7 days ago.

Reducing gap to 3 month is akin to an emergency kitchen sink response.

It's like complaining why didn't you shock a patient who wasn't in cardiac arrest or Vfib/Vtach.
This does not mean the roll out could not have been much faster and effective.

@john_actuary has shown we have consistently failed to close the eligibility gap ~6million even with 6 month dose gap with pace of 3rd doses. Image
Read 4 tweets
Nov 25, 2021
🧵 of 🧵's I found useful to understand B.1.1.529 (Nu) today. From actual subject matter experts or data journalists.

1/5
Tulio de Oliveira, the director of the Centre for Epidemic Response and Innovation in South Africa.

On the rapidly changing situation in SA and sequencing.

2/5

Jeffrey Barrett lead of Covid-19 genomics initiative @sangerinstitute

On the multitude of molecular effects of genomic sequence changes.

3/5

Read 5 tweets
Nov 25, 2021
The most robust data for vax effectiveness waning is from randomised control trials. Pfizer👇

2doses holds up well- but still complete the course and boost!

This is real world data. Prospective randomisation only reduces confounding we face in retrospective observations.

1/
Sources of bias/confounding in observational data (eg UKHSA case control study below):

▪️ accrued natural immunity in control (>45% 🏴󠁧󠁢󠁥󠁮󠁧󠁿 infected) & only a fraction tested
▪️ difficulty of retrospective matching/case controlling (high clinical risk vaxxed first, not just age)

2/
▪️ break throughs disproportionately sample higher risk (immunocompromised, preexisting conditions, etc)
▪️ lower test seeking behaviour in unvaxxed
▪️ pop highest risk of infection (urban, young, ethic minority, high deprivation) also lower vax uptake

3/
Read 9 tweets

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