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The dash for herd immunity

The home for all non-political Coronavirus (Covid-19) discussions on The Lemon Fool
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This is the home for all non-political Coronavirus (Covid-19) discussions on The Lemon Fool
Arborbridge
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Re: The dash for herd immunity

#425517

Postby Arborbridge » July 7th, 2021, 11:42 am

tjh290633 wrote:
I really do think that the "worried well" are spreading alarm and despondency.

TJH



I think that's a little unfair. There is a huge upswing in infections, and getting covid may not be "just a little snivel" as some people like to think. There can be a lot of suffering below hospitalisation level, you know. We still need to be sensible, because I for one do not wish to get ill - and I would think, neither do you as you are ten years older than me.

Unfortunately, the young and vigorous will be the ones on public transport who will be spreading disease. They will be the ones not wearing masks, even worse talking loudly and gufawing and coughing. I wouldn't mind so much if they behaved in a rather more dignified manner and kept themselves to themselves, but they won't. The worst offenders are those brash individuals between 25 and 45 - especially in groups with some drink. They just don't geddit.
The younger ones have learnt about covid protection in school and generally behave decently, I observe.

Arb.

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Re: The dash for herd immunity

#425528

Postby 88V8 » July 7th, 2021, 12:15 pm

tjh290633 wrote:
88V8 wrote:
tjh290633 wrote:I really do think that the "worried well" are spreading alarm and despondency.

Perhaps it's because they're been 'worried' that they remain well.

If the cap fits, wear it.

Ha! A beekeeper's hat with a veil. You could be onto something there.

V8

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Re: The dash for herd immunity

#425552

Postby 9873210 » July 7th, 2021, 1:40 pm

Snorvey wrote:
Snorvey wrote:I'm sure a couple of months ago that Imperial College had calculated that 80% of the UK population had COVID19 antibodies (Somewhat higher than other estimates at the time)


Correction: University College London, not Imperial College.

Bloomberg 10/04/2021

The U.K.’s increased Covid-19 immunity raises prospects of moving on from the worst of the pandemic, with some scientists saying the country could cross a key threshold as soon as Monday.

According to researchers at University College London, that’s when so-called herd immunity could be achieved in the U.K. Almost three-quarters of the population will have antibodies against the virus, either through vaccination or past infection, they estimate.


However:

Many other scientists think the U.K. is much further from herd immunity than UCL’s model suggests. It’s come under fire from some who say it overestimates the strength of vaccines and doesn’t adequately account for waning immunity and new virus variants. No more than 44% of the country has protection from Covid, according to estimates by Imperial College London.

But that was nearly 3 months ago. As a rough guesstimate, perhaps 25 million more jabbed since then?

https://www.bloomberg.com/news/articles ... trol-covid


With hindsight it is pretty clear there was no herd immunity on or around 10/04/2021.

But we should ask why University College was wrong. If it was just shoddy methodology we should just ignore pronouncements from this group. But it is possible there is something more interesting going on, such as the antibodies not predicting immunity.

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Re: The dash for herd immunity

#425611

Postby UncleEbenezer » July 7th, 2021, 4:42 pm

Arborbridge wrote:A guy from some transport organisation expressed the view yesterday tht he wants to see the end of mask wearing because it will encourage people to use buses and trains.


Yep. For the first time in a long time, I can travel further than I can cycle.

Oh well. Upside is, it's also cheaper, as I've just hit the age where I qualify for an old fart's railcard.

XFool wrote:Just a small fussy point by me, though I think it is a valid one, concerning the use of the term "herd immunity": AFAIK, "herd immunity" is the ONLY way to go with an infectious disease and always has been. There is, in fact, no other way to go...


Ultra-infectious: Foot and Mouth.
Also pretty infectious: smallpox. And a bunch of childhood diseases we grew up with that are now considered Big and Scary - like measles.

Herd immunity is a steady state, like the common cold.

Arborbridge
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Re: The dash for herd immunity

#425628

Postby Arborbridge » July 7th, 2021, 5:31 pm

UncleEbenezer wrote:
Arborbridge wrote:A guy from some transport organisation expressed the view yesterday tht he wants to see the end of mask wearing because it will encourage people to use buses and trains.


Yep. For the first time in a long time, I can travel further than I can cycle.

Oh well. Upside is, it's also cheaper, as I've just hit the age where I qualify for an old fart's railcard.

[quote="XFool"]

I not clear about this. What prevented you before? Nice empty trains: what's not to like?

Arb.

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Re: The dash for herd immunity

#425633

Postby jfgw » July 7th, 2021, 5:43 pm

UncleEbenezer wrote:Ultra-infectious: Foot and Mouth.
Also pretty infectious: smallpox. And a bunch of childhood diseases we grew up with that are now considered Big and Scary - like measles.


Foot and Mouth:
Cull and incinerate infectees. Restrict movement and disinfect.

Smallpox:
One of only two infectious diseases that have been eradicated. Eradication included vaccinating the population in the vicinity of known cases (i.e., giving them herd immunity).

Measles: Controlled by maintaining herd immunity through vaccination. Reduced levels of vaccination have allowed outbreaks to occur, including in the UK.

UncleEbenezer wrote:Herd immunity is a steady state, like the common cold.


Sufficient herd immunity could result in eradication (as happened with measles in most countries before vaccine hesitancy allowed it to return).

As XFool said, it is the only way to go.


Julian F. G. W.

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Re: The dash for herd immunity

#425641

Postby 1nvest » July 7th, 2021, 6:19 pm

Party time! Yay! A nationwide Vid-party, similar to the old Pox parties. Sooner or later you're going to get it, so best to get it all done during the summer months as they're anticipating a bad flu this winter. Or alternatively lock yourself away Howard Hughes style until you die.

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Re: The dash for herd immunity

#425643

Postby zico » July 7th, 2021, 6:30 pm

Some interesting graphs here.
For those of you who don't like to look at graphs, 57% increase in England hospitalisation over one week. Deaths on an upward trend (though data is "lumpy" due to thankfully very low starting numbers than for previous waves).

Just a bit of simple modelling here. weekly increases in both hospitalisation and deaths is around 57%.
If that increase continues over the next 8 weeks, then by the start of September, there will be 13,000 daily Covid admissions to hospitals, and 550 deaths.
(Increased number of vaccinations will help reduce this number, but 19th July (a.k.a. Freedom Day) is likely to increase the R-value above its current value)
I'm sure there are much more complex forecasts about, but this simple approach gives a broad outline of what is likely to happen unless there's some significant change. Most deaths are very likely to be from vaccinated people, because they will be by far the biggest population group, and even though the vaccination is a huge protection, this population group was the most vulnerable to start with.


On the regional graph, North-East looks particularly worrying (possible super-Delta variant?)

Daily vaccination numbers are actually going down compared with previous months.

Image

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Re: The dash for herd immunity

#425660

Postby dealtn » July 7th, 2021, 7:19 pm

zico wrote:
Just a bit of simple modelling here. weekly increases in both hospitalisation and deaths is around 57%.
If that increase continues over the next 8 weeks, then by the start of September, there will be 13,000 daily Covid admissions to hospitals, and 550 deaths.


In the last week there have been approx 200,000 infections found (no doubt a larger number exist).

Grow that at 57% - according to your simple model - and there will have been nearly 20 million more infections at the end of your 8 weeks.

There have been over 45 million people in this country vaccinated with at least one dose, and about 100,000 each day added to that list. Over 8 weeks that's nearly 6 million more people. The UK has a population size of only 68 million people.

At the end of your 8 weeks everyone will have had it, either by way of vaccination, or infection.

That's the problem with simple models, they rarely look like the real world, and whatever conclusions you draw from them are likely to have huge errors.

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Re: The dash for herd immunity

#425662

Postby Mike4 » July 7th, 2021, 7:30 pm

A further thought I forgot to include in my first post in this thread, is R0 has conveniently been forgotten by govt, the media and virtually all commentators. Dr John Campbell mentioned it briefly a week or two ago pointing out the Alpha variant is 40% more infectious than the original virus, and the Delta is 60% more infectious than Alpha. Now the original had a natural R0 of approx 3 so that means R0 for Delta must be 3 x 1.4 x 1.6 = 6.72.

Given we struggled to keep the original virus with R0 of 3 under control with our version of lockdown, I can see why the govt has not even bothered to try controlling Delta with it's R0 of 6.72, and elected to follow a strategy of letting it do whatever it likes.

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Re: The dash for herd immunity

#425666

Postby dealtn » July 7th, 2021, 7:37 pm

Mike4 wrote: Now the original had a natural R0 of approx 3 so that means R0 for Delta must be 3 x 1.4 x 1.6 = 6.72.



No it doesn't. Ro is based on an uninfected, and unvaccinated population. I think we can all agree that over time the population has changed such that many have been infected and many have been vaccinated.

The natural Ro for the original variant will be well below 3, and the Ro for subsequent variants will also be lower than you quote.

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Re: The dash for herd immunity

#425669

Postby Mike4 » July 7th, 2021, 7:50 pm

dealtn wrote:
Mike4 wrote: Now the original had a natural R0 of approx 3 so that means R0 for Delta must be 3 x 1.4 x 1.6 = 6.72.



No it doesn't. Ro is based on an uninfected, and unvaccinated population. I think we can all agree that over time the population has changed such that many have been infected and many have been vaccinated.

The natural Ro for the original variant will be well below 3, and the Ro for subsequent variants will also be lower than you quote.


It's not really very good form to tell someone they have their figures all wrong then fail to say what you think would be right.

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Re: The dash for herd immunity

#425672

Postby dealtn » July 7th, 2021, 7:56 pm

Mike4 wrote:
dealtn wrote:
Mike4 wrote: Now the original had a natural R0 of approx 3 so that means R0 for Delta must be 3 x 1.4 x 1.6 = 6.72.



No it doesn't. Ro is based on an uninfected, and unvaccinated population. I think we can all agree that over time the population has changed such that many have been infected and many have been vaccinated.

The natural Ro for the original variant will be well below 3, and the Ro for subsequent variants will also be lower than you quote.


It's not really very good form to tell someone they have their figures all wrong then fail to say what you think would be right.


I admit I don't know the answer. However I know the concept of Ro, and wasn't the person making the claim something "must be ..."

The whole rationale of herd immunity is based on the infection potential falling as the number remaining available to be infected falls. Further as that number falls the number able to carry the infection that others have the capability of catching it from also falls etc.

I'm sure you understand that concept, or at least I hope you do.

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Re: The dash for herd immunity

#425727

Postby 9873210 » July 7th, 2021, 11:40 pm

dealtn wrote:
Mike4 wrote: Now the original had a natural R0 of approx 3 so that means R0 for Delta must be 3 x 1.4 x 1.6 = 6.72.



No it doesn't. Ro is based on an uninfected, and unvaccinated population. I think we can all agree that over time the population has changed such that many have been infected and many have been vaccinated.

The natural Ro for the original variant will be well below 3, and the Ro for subsequent variants will also be lower than you quote.


R0, the basic reproduction number, is, as you say, always for a fully susceptible population. It does not change with the immunological status of the population.

Rt, the effective reproduction number, does vary with the immunological state of the population, and pretty much everything else. The t stands for time, some would write it as a function of time r(t).

Rt is of more interest in managing the pandemic. Rt will now be lower than R0 since some of the population is immune.

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Re: The dash for herd immunity

#425950

Postby 1nvest » July 8th, 2021, 6:37 pm

Snorvey wrote:
1nvest wrote:Party time! Yay! A nationwide Vid-party, similar to the old Pox parties. Sooner or later you're going to get it, so best to get it all done during the summer months as they're anticipating a bad flu this winter. Or alternatively lock yourself away Howard Hughes style until you die.

Or football matches as they are commonly known as.

Vid parties are broader, include nightclubs etc. Which were even still plentiful during 'lockdown' such as using personal headphones to eliminate the otherwise external base boom telltale. I suspect many of the sub-30's don't need a vaccination as they've already had the Covid months ago.

Other non-third countries such as Ireland actually policed lockdown, where even driving/walking a few miles into town would encounter authorities. Here, policing was very minimal, more often a single night purge in one area that soon became broadcasted.

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Re: The dash for herd immunity

#425990

Postby XFool » July 8th, 2021, 10:19 pm

Vaccine uptake in England almost halves ‘amid mixed messages’

The Guardian

Demand from under-30s slows, with Manchester and Sheffield health chiefs noting ‘false sense of security’

"Covid-19 vaccine uptake in England has almost halved over the past fortnight, with health experts blaming mixed government messaging about normality returning on 19 July."

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Re: The dash for herd immunity

#426463

Postby zico » July 10th, 2021, 2:55 pm

Mike4 wrote:A further thought I forgot to include in my first post in this thread, is R0 has conveniently been forgotten by govt, the media and virtually all commentators. Dr John Campbell mentioned it briefly a week or two ago pointing out the Alpha variant is 40% more infectious than the original virus, and the Delta is 60% more infectious than Alpha. Now the original had a natural R0 of approx 3 so that means R0 for Delta must be 3 x 1.4 x 1.6 = 6.72.

Given we struggled to keep the original virus with R0 of 3 under control with our version of lockdown, I can see why the govt has not even bothered to try controlling Delta with it's R0 of 6.72, and elected to follow a strategy of letting it do whatever it likes.


AstraZeneca vaccine reduces infection rates by around 50%.

If everyone was vaccinated, that would give R0 = 6.72*.5% = 3.4

Currently, with only 50% of UK population fully vaccinated R0 will be halfway between 3.4 and 6.7 = 5
(I haven't taken account of the proportion of people with just one vaccination, but one jab only reduces infection by 30%, and also infections are being mostly spread amongst children (completely unvaccinated) and young people without vaccinations who are more likely to be spreaders, based on their lifestyles.

Given this, the R0 may be around 4 rather than 5, but it's very unlikely to be much lower - and the crucial point is that it will be spreading more quickly than the original Wuhan virus did when it first arrived on our shores.

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Re: The dash for herd immunity

#426471

Postby dealtn » July 10th, 2021, 3:26 pm

zico wrote:
Mike4 wrote:A further thought I forgot to include in my first post in this thread, is R0 has conveniently been forgotten by govt, the media and virtually all commentators. Dr John Campbell mentioned it briefly a week or two ago pointing out the Alpha variant is 40% more infectious than the original virus, and the Delta is 60% more infectious than Alpha. Now the original had a natural R0 of approx 3 so that means R0 for Delta must be 3 x 1.4 x 1.6 = 6.72.

Given we struggled to keep the original virus with R0 of 3 under control with our version of lockdown, I can see why the govt has not even bothered to try controlling Delta with it's R0 of 6.72, and elected to follow a strategy of letting it do whatever it likes.


AstraZeneca vaccine reduces infection rates by around 50%.

If everyone was vaccinated, that would give R0 = 6.72*.5% = 3.4

Currently, with only 50% of UK population fully vaccinated R0 will be halfway between 3.4 and 6.7 = 5
(I haven't taken account of the proportion of people with just one vaccination, but one jab only reduces infection by 30%, and also infections are being mostly spread amongst children (completely unvaccinated) and young people without vaccinations who are more likely to be spreaders, based on their lifestyles.

Given this, the R0 may be around 4 rather than 5, but it's very unlikely to be much lower - and the crucial point is that it will be spreading more quickly than the original Wuhan virus did when it first arrived on our shores.


Imagine a game where you enter a large room that has 1,000 people in it all with a bright tag attached by a piece of velcro to their back. You are allowed into the room and given 5 seconds to remove a velcro tag and are a winner if you succeed in that 5 seconds. The tag isn't put back on and the same individuals remain in the room.

Another contestant is allowed 5 seconds to play the game, with 999 people having a tag. It is likely you both will have succeeded.

But that's a linear version and it seems most agree Covid doesn't work like that it is "exponential". So for round 2 instead of a single contestant playing there are 2 people searching for those bright velcro tags. Again both will probably succeed and there will be 997 tags remaining and 3 people without.

Now 4 people play round 3, 8 play round 4 etc. It's not hard to imagine there comes a point, perhaps at this round where only 7 of the 8 win, or 15 of the 16 etc. The game is becoming harder to win at for any individual. After a few rounds most contestants aren't able to win. There is a developing "herd immunity" to the grab a tag game.

Now maybe the rules change and instead of having 5 seconds to grab the tag, you get 10. This new version of the game is more infectious than the first version. The number of rounds before the game becomes harder alters, and so does the number of rounds taken and contestants playing to get 50% of the tags, or 90% or 99%. It doesn't alter the fact that the game gets harder the more rounds you progress.

Nor is it intuitively obvious whether it is easier in round 1 of version 1 of the game, or round 3 (or 4 or 10) of the second version of the game.

In focussing solely on Ro, of either version of the game, and ignoring the number of rounds played, and the diminishing number of tags and only comparing the number of seconds between 5 and 10 allowed in those 2 versions of the game misses a whole lot of what is important, which is how many tags have been taken, and how many are left.

Now imagine a version of the game, developed in Oxford, where at the end of each round 100 of the people in the room are removed from the game to "safety". That makes it harder still to find a "tag" to grab. If the numbers being removed is sufficiently large, the effect of removal is greater than the increase from 5 to 10 seconds.

No doubt there could be many modelled versions of the game with attempts to work out a way to ensure the fewest tags are won by contestants. No doubt some would only focus on the number of seconds in the rules, and not the other variables. It wouldn't surprise me if some people thought that in every version of the game all the tags would always be got. A larger number would possibly believe there would be similar outcomes regardless of how the variables would change, and that the original rules should always apply and no variation in strategies in "surviving" playing should be allowed.

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Re: The dash for herd immunity

#426488

Postby jfgw » July 10th, 2021, 4:39 pm

Most (all?) people will have tags, it is just that some will be tiny and difficult to find. People who have both had Covid and received two jabs will have tags that are very difficult to find, whereas refuseniks who have yet to be infected will have much bigger, brighter tags.

Some people have better eyesight than others and are much better at finding tags (and may find lots of them) whereas some other people will not find any.

I still prefer the vampire analogy!


Julian F. G. W.

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Re: The dash for herd immunity

#426492

Postby dealtn » July 10th, 2021, 4:54 pm

jfgw wrote:Most (all?) people will have tags, it is just that some will be tiny and difficult to find. People who have both had Covid and received two jabs will have tags that are very difficult to find, whereas refuseniks who have yet to be infected will have much bigger, brighter tags.

Some people have better eyesight than others and are much better at finding tags (and may find lots of them) whereas some other people will not find any.

I still prefer the vampire analogy!


Julian F. G. W.


Absolutely fine, add other variables. Just makes it all the more reason not to solely focus on the importance of whether it is 5 or 10 seconds (or the original Ro) that is the thing to be doing.


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