Covid-19 Gambles

Notch7 said:

John -this thread is very interesting -the debate is scientific which has so far avoided the emotive, political arguments that fester most covid threads

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Yes, interesting. There have been a few attempts to inject 'emotive political arguments', but I (and, thankfully, everyone else) has simply ignored them. We also have been hearing from at least one person with fairly strong views, in a direction with which many might not agree - but, again, that is fine (the subject certainly deserve a diversity of opinions being voiced), provided that it remains essentially scientific and doesn't become too 'emotional' (and certainly not 'political').

Some have asked why I started this thread in this forum - but, had I started it in GD (a place I keep many barge-poles away from), I hate to think how the 'discussion' would have evolved - so I hope that not too many are annoyed by it being here (and they can, of course, simply ignore it if they so wish).

Kind Regards, John

JohnW2 said:

echoes said:

The UK (and everywhere else) will achieve herd immunity one way or another. Whether vaccination plays a significant part of this outcome is unknown, but with significant numbers of cases and hospitalizations among the vaccinated, it's looking like immunity via exposure is more reliable.

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I'm no virologist or immunologist but, from what little I know about those subjects, my intuitive view would probably be as you suggested - that exposure to an entire pathogen (by their millions/billions) when infected would result in a more robust immune response than does targeting 'just a few little bits' of the pathogen with a vaccine. However, my intuition is presumably wrong, because those who know much more than I do (essentially JCVI) have consistently advised that even those who have had laboratory-confirmed severe Covid-19 infection should nevertheless still be vaccinated.

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@Swwils has kindly explained a lot of the issues to me, but another sort-of-related thought has now occurred to me ...

The 'Herd Immunity Threshold' (HIT) is directly related to the transmissibility of a virus which, in the total absence of any measures to restrict transmission will be represented by "R0". As we know, R0 (hence HIT) is greater for the delta variant than previous ones, and it wouldn't surprise me if it were 80% or above for the delta variant. If that were the case then, as I've said, achieving herd immunity by vaccination alone would not be achievable if we don't even offer vaccination to about 20% of the population (the under-18s).

However, what has just further occurred to me is that, on the basis of my understanding of the theory, the HIT relates to the proportion of totally immune people in the population. If that's the case, then even if we did manage to vaccinate 80% of the population, then, if the vaccine was, say '90% effective' in preventing infection, that would be 'equivalent' (in terms of HIT) to having 72% of the population 'totally immune' (and if it were only 80% effective, the equivalent of 64% 'totally immune').

I therefore suspect that it may be challenging, perhaps even mathematically impossible, to achieve 'herd immunity' (for the delta variant, or worse) by vaccination alone with vaccines that are appreciably less than '100% effective", particularly if we don't vaccinate the under-18s.

I don't know enough about the 'effectiveness' of 'natural immunity' (due to infection) to be able to formulate a view about herd immunity due exclusively, or partially, to that.

Any thoughts/comments.

Kind Regards, John

Ive done a very quick scan of the literature.

It seems that there are issues. Natural immunity is very prone to variant variation. From a French study:
Unvaccinated health care workers appeared to have less protection against the delta and beta variants compared with alpha about a year after they recovered from mild COVID-19. While 88% of this group had neutralizing antibodies against alpha, only 47% neutralized delta.

And a US study:

However, their plasma had less neutralizing activity against the variants B.1.1.7 (alpha), B.1.351 (beta), B.1.526 (iota), and P.1 (gamma), with the greatest loss of activity against the beta variant first detected in South Africa

That last part could well go someway to explain the new policy regarding travel to France, as I understand Beta levels are quite high there.

However, prior infection and even a single vaccine dose seems confer high levels of immunity, across a broad range of variants, so hopefully as more become vaccinated, we will see positive trends.

However, as long as the virus is endemic (which I can't see an end too, since the vaccine doesn't prevent infection), there is scope for further mutations, one or more of which could certainly evade even a high level of immunity, and even if not, those unable to be vaccinated or at risk due to underlying conditions won't be safe

JohnW2 said:

However, what has just further occurred to me is that, on the basis of my understanding of the theory, the HIT relates to the proportion of totally immune people in the population. If that's the case, then even if we did manage to vaccinate 80% of the population, then, if the vaccine was, say '90% effective' in preventing infection, that would be 'equivalent' (in terms of HIT) to having 72% of the population 'totally immune' (and if it were only 80% effective, the equivalent of 64% 'totally immune').

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Surely it means that all of the 80% are only 90% immune - i.e. not immune.

mikeey84 said:

It seems that there are issues. Natural immunity is very prone to variant variation. ...

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Indeed, that was one of Swwil's main points about the potential advantage of (mRNA) vaccines, as compared with infection, as a cause of immunity - which, as I said to him, I can understand.

However, as I also said to him, everything he said seemed to relate to mRNA vaccines, leaving me to wonder whether the ("traditional") vaccine given to the likes of me is as likely to offer as much advantage (in relation to 'natural immunity') over variants as do mRNA vaccines.

mikeey84 said:

However, as long as the virus is endemic (which I can't see an end too, since the vaccine doesn't prevent infection), there is scope for further mutations, one or more of which could certainly evade even a high level of immunity, and even if not, those unable to be vaccinated or at risk due to underlying conditions won't be safe

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That's the point I keep making, and one of my main reasons for 'concern'. Whilst is is probably unlikely that a variant comes along which shows a catastrophic degree of 'escape' from current vaccines, it's not impossible - and could theoretically happen 'tomorrow'. All we can do to minimise that risk is to take steps to reduce the frequency and number of any mutations/variants (any of which could, theoretically, be 'catastrophic'), and allowing the number of infected people to 'soar' (which we have been allowing to happen, and today have exacerbated) is the antithesis of such a policy!

Kind Regards, John

JohnW2 said:

However, as I also said to him, everything he said seemed to relate to mRNA vaccines, leaving me to wonder whether the ("traditional") vaccine given to the likes of me is as likely to offer as much advantage (in relation to 'natural immunity') over variants as do mRNA vaccines

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It seems the best idea is to get a mild infection, and then a vaccine:

However, recovered health care workers who had received 1 dose of the AstraZeneca, Pfizer, or Moderna vaccines had a marked increase in neutralizing antibody levels against all 3 of these variants compared with their unvaccinated peers.

Hopefully therefore, if the AZ vaccine means you get a mild infection (vs an unvaccinated person), vaccine+ infection antibodies will give you a very high level of protection.

EFLImpudence said:

Surely it means that all of the 80% are only 90% immune - i.e. not immune.

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Indeed it does - but, as I said, as far as the theory/maths of HIT calculation is concerned, that is equivalent to 72% being '100% immune'.

The usual standard calculation of HIT ends up with a figure for the proportion of "100% immune" people there have to be in the population to achieve 'herd immunity'.

It doesn't require any knowledge of rocket science to understand that if all the vaccinated people are (on average) less than "100% immune", one needs a higher proportion of vaccinated people in the community (to achieve 'herd immunity') than would be the case if they were all "100% immune"

Also, it may sound a little pedantic, but the reason I included "(on average)" above is that it's probably not really true to say that "...all of the 80% are only 90% immune". For a given degree of exposure to virus, the true situation is probably much closer to "90% are "100% immune" and 10% are "0% immune" - since one either does, or does not, become (clinically) infected following a certain degree of exposure.

Kind Regards, John

mikeey84 said:

It seems the best idea is to get a mild infection, and then a vaccine:

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Maybe, but to have had such a 'policy' would have been seriously flawed, for reasons that seem so obvious that I won't bother to go into them (unless someone wants me to).

mikeey84 said:

However, recovered health care workers who had received 1 dose of the AstraZeneca, Pfizer, or Moderna vaccines had a marked increase in neutralizing antibody levels against all 3 of these variants compared with their unvaccinated peers.

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Interesting.

mikeey84 said:

Hopefully therefore, if the AZ vaccine means you get a mild infection (vs an unvaccinated person), vaccine+ infection antibodies will give you a very high level of protection.

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Hmmmm. Does that mean that, having had my two doses of AZ, I should be 'hoping' that I now get a mild infection?

As I hinted yesterday, if they do decide to give the likes of me a booster later in the year, it will be interested to see which vaccine they decide to give me.

Kind Regards, John

JohnW2 said:

Maybe, but to have had such a 'policy' would have been seriously flawed, for reasons that seem so obvious that I won't bother to go into them (unless someone wants me to).

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I said this with tongue in cheek, but that doesn't always come across on the Internet!

mikeey84 said:

I said this with tongue in cheek, but that doesn't always come across on the Internet!

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Indeed - and I often fall foul of that. Emoticons can help.

Kind Regards, John

Swwils said:

There is not yet solid indication of vaccine hesitancy in younger groups, especially since many will have to rearrange due to 28 day limits. What you may be feeling is the effect of a comparatively slower rate of vaccination.

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For what it's worth, in today's Press Conference it was said that, although all 18-29 year-olds have now been 'offered' vaccination, there are currently around 3 million of them who have not yet 'responded to that invitation'. I obviously don't know whether that's just because they have not yet "got around to responding" or some other reason. I suppose we will discover that over the coming weeks.

Kind Regards, John

echoes said:

In light of this high efficacy, I'm finding it hard to reconcile the current seemingly 50/50 or so split in hospitalizations. Is this to be expected or not?

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In today's Press Conference, in response to the question, Patric Vallance say that about of 16% of currently hospitalised patients have been 'double vaccinated' - so I again have to wonder where your "50/50" figure comes from.

He also made the point, which would seem to be totally valid, that, since vaccines do not give 100% protection against serious illness (hence hospitalisation), it is to be expected that as the proportion of 'doubly vaccinated' people in the population rises, so will the proportion of hospitalised people who have been 'double vaccinated'.

That's obviously true. If one considers the hypothetical situation in which the proportion of the population who had been double vaccinated approached 100%, then the proportion of those who were hospitalised (despite vaccination) would also, inevitably, approach 100%.

To examine the issue you were alluding to, one would need to compare the proportions of vaccinated and unvaccinated people who were ending up in hospital - which clearly is totally different from looking at the proportion of hospitalised people who have been vaccinated.

Kind Regards, John

JohnW2 said:

The 'Herd Immunity Threshold' (HIT) is directly related to the transmissibility of a virus which, in the total absence of any measures to restrict transmission will be represented by "R0". As we know, R0 (hence HIT) is greater for the delta variant than previous ones, and it wouldn't surprise me if it were 80% or above for the delta variant. If that were the case then, as I've said, achieving herd immunity by vaccination alone would not be achievable if we don't even offer vaccination to about 20% of the population (the under-18s).

However, what has just further occurred to me is that, on the basis of my understanding of the theory, the HIT relates to the proportion of totally immune people in the population. If that's the case, then even if we did manage to vaccinate 80% of the population, then, if the vaccine was, say '90% effective' in preventing infection, that would be 'equivalent' (in terms of HIT) to having 72% of the population 'totally immune' (and if it were only 80% effective, the equivalent of 64% 'totally immune').

I therefore suspect that it may be challenging, perhaps even mathematically impossible, to achieve 'herd immunity' (for the delta variant, or worse) by vaccination alone with vaccines that are appreciably less than '100% effective", particularly if we don't vaccinate the under-18s.

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Now, I'll preface my response with things like "I didn't fully follow the maths", and "it was a while ago", and ...
I vaguely recall a program on TV a while ago which looked at this - but I vaguely recall it was something like an repeat of Bang Goes the Theory from before the covid pandemic kicked off - it could have been Series 8 Episode 5 from 2014 which according to the BBC site was last on on Thu 4 Mar 2021. One piece looked at what proportion fo the population needed to be be vaccinated and how this varied with vaccine effectiveness and R0. It was ... rather sobering Again, it's only vague recollection, but a small change in a variable made the difference between needing something like 95% to needing 98% (yes, all but 2% of the population) to be vaccinated in order to achieve herd immunity and have a stable or declining infection rate. Put another way, 80% vaccination wasn't going to cut it for the numbers they used.
Considering it was filmed something like 5 years before covid, it was very topical

JohnW2 said:

In today's Press Conference, in response to the question, Patric Vallance say that about of 16% of currently hospitalised patients have been 'double vaccinated' - so I again have to wonder where your "509/50" figure comes from.

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Edit: I'm not now even certain that his correction was correct. And I'm weary of having to check govt statements and stats. I assume now by default that they are dishonest or obfuscated.

I've enjoyed reading the vaccine efficacy discussion. It's not something I've done much independent research into, so thanks to those who have.

As might be expected in this 'parish', there's been a lot of detailed discussion on narrow topics, but nobody's really responded to my question on whether lockdown will be, in the final analysis, successful or proportionate or damaging and disproportionate.

My view is that lockdown has turned a public health crisis into not only a public health crisis, but an economic crisis, an education crisis, a mental health crisis, a democratic crisis, a legal crisis and a moral crisis.

We cannot judge lockdown on sole criterion of suppressing Covid, even if it can be demonstrated that it had some limited effect (which is very much contested).

I've always thought it disproportionate, and I suspect we will learn just how much over the years to come.