The IoM (as UK is) is undergoing a natural wave where COVID will move through the low risk groups until we reach herd immunity. At present
(19th July) 64,400 1st jabs over population 84,584, if all these get 2nd jab, 2+2 coverage will be 76% we need 85%+ for herd immunity.(1/n)
(19th July) 64,400 1st jabs over population 84,584, if all these get 2nd jab, 2+2 coverage will be 76% we need 85%+ for herd immunity.(1/n)
Let's assume we had 5K real infections over prior waves (1,500 known + plenty unknown). So have roughly 15,000 potential hosts now with no jabs (mainly children). If apply the standard SEIR model of infectious disease outbreak (system 4 ODEs) with the following parameters: (2/n)
R = 3.4 (drop 1.12 day 37 due risk aversion)
Hosp rate = 1.23%
Time Hospital avg = 9.4 days
You get:
8,185 infected (bulk over 80 days)
Peak hospitalisation 22 at day 60
And obtain 85%+ hosts with anti-bodies and hence herd immunity.
(3/n)
Hosp rate = 1.23%
Time Hospital avg = 9.4 days
You get:
8,185 infected (bulk over 80 days)
Peak hospitalisation 22 at day 60
And obtain 85%+ hosts with anti-bodies and hence herd immunity.
(3/n)
Critical:
2+2 High risk should shield around peak of natural wave.
Suggest at least 1 week prior to peak number infectious and 2 weeks after, peak obtain day 37.
While 'natural wave' is in progress, no additional value is provided by any 2+2s becoming infected.
(4/n)
2+2 High risk should shield around peak of natural wave.
Suggest at least 1 week prior to peak number infectious and 2 weeks after, peak obtain day 37.
While 'natural wave' is in progress, no additional value is provided by any 2+2s becoming infected.
(4/n)
To best my knowledge I calibrated the standard SEIR model, after many discusses with others. See details within following posts imagine. SEIR model is established and implementation used robust. Following posts will illustrate various stages of wave progression. (5/n)
Calibration AFAIK is best fit to reality we face. An 'intervention' on day 37 was used to reflect people becoming risk averse, in reality this will be sliding scale rather than single event, but shift in R on day 37 net-net will have a very similar effect on dynamic. (6/n) 
Peak Infections:
Day 38 will see a peak in the number of COVID+ infectious hosts actively circulating. It is critically important that 2+2 high risk groups minimise the risk of infection during natural wave and the risk
of infection is expected to peak on this date. (7/n)
Day 38 will see a peak in the number of COVID+ infectious hosts actively circulating. It is critically important that 2+2 high risk groups minimise the risk of infection during natural wave and the risk
of infection is expected to peak on this date. (7/n)
Note, number in Nobles will still be way off the peak at this time. My personal view is that shielding at least a week prior to this date and 2 weeks afterwards would provide the greatest reduction in risk for 2+2 for the number of days in isolation. (8/n)
Peak Hospitalisations
Peak hospitalization expected to occur on day 56 at 22 occupied bed. I assumed the average stay in hospital will be 9.42 days, which considering the younger age groups may turn out to be much too high. (9/n)
Peak hospitalization expected to occur on day 56 at 22 occupied bed. I assumed the average stay in hospital will be 9.42 days, which considering the younger age groups may turn out to be much too high. (9/n)
However, when estimating likely demand for Nobles beds, for planning purposes I would heavily skew calibration numbers towards a reasonable worst case scenario. (10/n)
Day 80
At this stage 7,682 (52.03%) have been removed from the pool of potential infectious hosts. 83.28% of total expected infections over natural wave would have already occurred. The number of infectious in circulation now expected to have dropped from peak 763 to 102. (11/n)
At this stage 7,682 (52.03%) have been removed from the pool of potential infectious hosts. 83.28% of total expected infections over natural wave would have already occurred. The number of infectious in circulation now expected to have dropped from peak 763 to 102. (11/n)
Day 100
Infectious in circulation now dropped from 102 on day 80 to 25. The natural wave risk to 2+2 high risk groups have now also completely abated.
(12/n)
Infectious in circulation now dropped from 102 on day 80 to 25. The natural wave risk to 2+2 high risk groups have now also completely abated.
(12/n)
Day 160
End of natural wave, with net outcome being that from the original population of 14,765, we have 6,580 (44.57%) still susceptible to infection (not immune), 8,178 (55.39%) who are deemed immune to infection.
(13/n)
End of natural wave, with net outcome being that from the original population of 14,765, we have 6,580 (44.57%) still susceptible to infection (not immune), 8,178 (55.39%) who are deemed immune to infection.
(13/n)
Effect of Natural wave on Herd Immunity
Original 64,400 2+2s are now joined by further 8,178 members, to create a set of 72,578 2+2 equivalents. This over total population of 84,584 equates to 85.8% of population. At which point the IoM just about achieves herd immunity. (14/n)
Original 64,400 2+2s are now joined by further 8,178 members, to create a set of 72,578 2+2 equivalents. This over total population of 84,584 equates to 85.8% of population. At which point the IoM just about achieves herd immunity. (14/n)
Though future cases of COVID could be imported into IoM, the dynamics of any outbreak would significantly differ. For example, you may see localised small outbreaks within a school but we are not going to experience national mass infections (for the existing variants). (15/n)
Which Day are we on now?
The above SEIR model assumes that one COVID+ seeder was introduced into the community and the natural wave was allowed to take its natural course. Known possible ground zero was reported case at CRHS 20 days ago. (16/n)
The above SEIR model assumes that one COVID+ seeder was introduced into the community and the natural wave was allowed to take its natural course. Known possible ground zero was reported case at CRHS 20 days ago. (16/n)
Existing border policies will continue to introduce seeders into the community. For small numbers (start of wave) there are probabilistic effects which can lead to waves dying out but I am very highly confident that existing natural wave ground zero was 15-20 days ago.(17/n)
My reaction:
In short, it is what it is. I feel the Dunkirk Spirit, and can only repeat the words of our Head of State the Queen, "we will succeed and the success will be due to everyone of us", and her speech is as relevant now as it was then: (18/n)
In short, it is what it is. I feel the Dunkirk Spirit, and can only repeat the words of our Head of State the Queen, "we will succeed and the success will be due to everyone of us", and her speech is as relevant now as it was then: (18/n)
Disclaimer: The above model was created in good faith, to the best of my understanding of the reality we face. Any feedback much appreciated, and publicly shared versus only share with friends and family, in belief (rightly or wrongly) that it may help others. (n/n)
Supplementary material on calibrated SEIR model of the IoM Natural Wave. Detailed (after queries) why R I quoted differs from (organic) R of Delta variant, and its interplay with Herd Immunity Levels required & the setting R=1.1 on Day 37.
(n+1/n) sites.google.com/webcabcomponen…
(n+1/n) sites.google.com/webcabcomponen…
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