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

26 May
70% [68,72] of England's Total population have now been infected or vaccinated.

Wall of immunity:

13% Infected
44% Vaccinated 1+
13% Both

Usual caveats: time lag after vax, not 100% protective, assumes random vaxxing probability of previously infected etc.

Estimated numbers of people:

7.0m Infected only
24.7m Vaccinated only
7.5m Infected & vaccinated

17.1m unexposed and susceptible

The remaining 17.1m unexposed/susceptible population is heavily skewed to younger age groups.

2/3 under 25
1/3 in school age kids 5-14yo

Outbreaks and cases will expectedly be concentrated in these groups now and increasingly <18 after current vax roll out plan completed.

Read 5 tweets
23 May
Grateful for the hard work of dedicated public health scientists at @PHE_uk like @kallmemeg and unsung others who work overtime to produce excellent reports on the variant of concern B1.617.2 🇮🇳

🧵analysis of vax effectiveness, and why interpretation of reduced VE limited.

PHE did a 'test negative case control study' w/ logistic regression as I outlined yday.

From test and vax databases they retrospectively created a control cohort of 99k who tested negative and compared to 6.4k test positive for B117 & 1k for B1.617.2


PHE found a statistically significant dip in symptomatic protection after 1 vax dose.

51% ➡️ 33% against B1.617.2 variant (yellow).
For both Pfizer and Ox/AZ (21 days after 1st dose).

No statistically significant change after 2 vax doses (14 days after 2nd dose).

Read 21 tweets
22 May
This is good news.

The longer it takes to statistically tell difference between vax effectiveness against variants the smaller the actual dip (if any) in protection will be.

In randomised control trials we can be confident in vax effect after only 100+ infections because selection bias and confounding variables between the vaxxed and unvaxxed comparison populations are (e)limited by the randomisation process.

This is not the case when we do retrospective observational studies - like vax effectiveness against variants in the field.

The statistical analysis is more challenging. There are biases in who is vaxxed or infected, living, working, mixing patterns, medical health/immunity.

Read 7 tweets
16 May
JCVI extension of vax dosing interval to 12 weeks is a great public health decision.

3.5X higher peak antibody levels w/ Pfizer if delayed boost vs 3 week.

Really important for protection against variants and duration esp in vulnerable🧵


We kept seeing 1 dose vax after prior infxn boosting Ab tires 3X higher than 2 doses at the standard 3 week interval. Some of us wondered if this was from optimised prime-boost interval at the time...

It now looks like a probable explanation.


3 weeks on short side of intervals, where immune response hasn't completely matured after prime stimulus.

Delay may selectively expand population of long lived plasma cells (B cell derivatives) too.

Delayed boost shown to have better Ab response across prev vax types👇

Read 15 tweets
29 Apr
Fantasy commentary letter in Lancet (not a peer reviewed study)!

It's an unreasonable proposition for most countries like the UK to achieve elimination + constraints of reality negates claimed economic and liberty benefits if attempted...


Despite pre-flight screening and quarantine Australia and New Zealand have failure rate of 4.8 per 100k travellers. SARS-COV-2 cases slip through!


Those cases slipping through results in necessary lockdown (regional or state wise) to eliminate community transmission.

Up to January 31, 2021:
Australia 7 failures, with 1 causing 800 deaths
New Zealand 9 failures, 1 causing an outbreak of 3 deaths

more since

Read 18 tweets
28 Apr
PHE study on household transmission after vax:

40-50% reduction if break through infxn

From contact tracing of 4.1k households where index vaxxed >21days and contact positive 2-14 days of index

4 Jan 4 - 28 Feb from 365k households w/ single index case and 1m+ contacts

1/ Image
No statistical difference between Ox/AZ and Pfizer efficacy for onward transmission

No statistical difference in effect by age

Well controlled:
adjusted for age of index case and contact, sex, region, calendar week, index of multiple deprivation quintile, household type


Pillar 2 symptomatic case only so may miss asymptomatic cases (=overestimate efficacy).
Assumed contact symptom >2days of index was transmission but cd be co-primary (=underestimate),
and all 2-14 days are household transmission not independent (=underestimate)

Read 4 tweets

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