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Karl Friston’s pandemic modelling

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 Bob Kemp 16 Oct 2020

This is intriguing, with evidence both for and against the circuit-breaker idea:


 Yanis Nayu 16 Oct 2020
In reply to Bob Kemp:

What doesn't seem to be considered in that is whether an effective vaccine will be found in a timely manner.  If it is, efforts like lockdowns will reduce deaths overall by marking time and delaying the inevitable until it can be controlled by the vaccine.  If no vaccine arrives, or it's ineffective or too late, the only point of all the measures is to prevent the NHS being overloaded and to shield the most vulnerable.

 wintertree 16 Oct 2020
In reply to Bob Kemp:

My take is the same as for modelling in the early days.  It's not predictive in any trustworthy capacity, but gives a good way to interpret and understand data.

There are so many unknowns in our situation that any model is full of "free parameters" (in modelling parlance).  Free parameters are of two sorts:  

  1. Explicit ones - values that aren't known but are used by the model (e.g. what fraction of people have cross-immunity pre-dating the emergence of the virus).
  2. Implicit ones - human decisions of what mathematical terms to include in the model and what to exclude.

In producing a model, the free parameters are adjusted until the model fits the data.  With too many free parameters a "wrong" model can be adjusted until it fits the existing data perfectly, but its predictions don't go on to match reality as it pans out.  This was clearly the case with the Ferguson model of the early days where the social mixing matrix alone represented more free parameters than the number of days of data the model was being fit to.  With Friston's models, he's still got critical free parameters in there and whilst there is more data to fit too, I'm not convinced it explores the state space of the model well enough (state space meaning all the different sorts of things that could be going on, loosely speaking) that it can be usefully predictive.

His forecast for deaths from a second wave seems optimistic, depending on what happens with policy and public compliance.

Ultimately, I maintain that if we knew enough to make a trustworthy model prediction, we would know enough to know exactly which risk control measures would stop the virus dead in its tracks with surgical precision rather than broad lockdown, and we wouldn't need the model - the same unknowns apply to both.

Good old fashioned best practice in infection control drawn from a century of epidemiology is what we need now. 

Post edited at 18:37
 DancingOnRock 16 Oct 2020
In reply to Yanis Nayu:

Phase 3 trail results are to be released ‘either this week’ - too late now I guess. Or by the first week of November. 

There will then be a lot of lobbying within the EU over accelerated authorisation. 

People being put into tier 3 will be lobbying hard. Early January or maybe before for roll out. I have a gut feeling ‘very’ vulnerable people will be vaccinated in December as part of ‘Phase 3 extended trials’.

 cb294 17 Oct 2020
In reply to DancingOnRock:

According to rumours going around at university the Pfizer/Biontec vaccine is about to be granted emergency use authorisation in November or December the latest in the US and possibly the EU.


edit: Also, and that is not merely a rumour, one of the vaccine companies has just bought a major production plant at our local biomed campus from another pharma company that is not in the Covid vaccine race, and expects entering vaccine mass production still in 2020.

They would not rush such an investment if they did not at least have positive indications from the trials.

I am quite hopeful that the spike of winter 2021/22 will already be blunted by mass vaccination. Just ten more months of distancing and quarantine measures to get through .....

Post edited at 11:57
 DancingOnRock 17 Oct 2020
In reply to cb294:

I was laughed at here when I suggested something similar to this a few weeks ago. 

BBC news has just shown people queuing up and paying for a vaccine somewhere. I missed where it was. 

Edit - scrap that, it was China for vaccine that’s not completed trials. 


Post edited at 13:16
 cb294 17 Oct 2020
In reply to DancingOnRock:

Even if one the current candidates gets emergency approval we will be roughly where the Russians are since a couple of months and got widely slagged off for.

There will at best be a limited amount of doses available, first for e.g. nursing staff on covid wards, then for more general medical personnel, care home staff, then maybe teachers or bus drivers. It will only be enough to remove potential super spreaders and protect those with very highest risk of infection.

Sufficient vaccine to shield vulnerable people (care home residents, then generally people over, say, 70) will be available next late spring, summer at the earliest. We will have to get through this winter without that help, and plan accordingly. Hopefully we will be ready for 21/22.


In reply to DancingOnRock:

I volunteered to make a £100 donation to a charity of your choice if there was mass vaccination before Christmas.

I stand by that. I’ll be surprised if we see it that soon, but I will also be very happy to be wrong.

Lets define as 0.5m doses administered in the U.K. post regulatory approval.

You just name the charity.

 DancingOnRock 17 Oct 2020
In reply to The New NickB:

I can’t find the thread, but don’t recall saying mass vaccinations. Just that they’d start roll out by the end of October, beginning of November. 

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