😱Enter Herd Immunity
How Dutch policy makers may have misjudged the COVID-19 pandemic.
How Dutch policy makers may have misjudged the COVID-19 pandemic.
Introduction
March 16th 2020 prime-minister Mark Rutte addressed the Dutch nation with regards to the COVID-19 strategy the Netherlands was about to follow during the COVID-19 pandemic. This strategy was confidently presented as a ‘maximum control’ strategy, ...
March 16th 2020 prime-minister Mark Rutte addressed the Dutch nation with regards to the COVID-19 strategy the Netherlands was about to follow during the COVID-19 pandemic. This strategy was confidently presented as a ‘maximum control’ strategy, ...
aimed at not to exceed the ICU capacity and protect the old and vulnerable by the progressive build-up of herd immunity in the lower age cohorts. The ministerial crisis management committee (OMT) had already advised the government to implement several suppressive measures, ...
which included among others the advice to refrain from handshaking, enforced social distancing (1.5 m) and a ban on mass gatherings.
Aforementioned measures were implemented nation-wide at about March 12th 2020. In addition people were advised to work from home and to stay ...
Aforementioned measures were implemented nation-wide at about March 12th 2020. In addition people were advised to work from home and to stay ...
at home in case cold-like or influenza like symptoms had developed, with a 38 degrees centigrade threshold. Medical and care home staff were deemed vital, they were not handed any personnel protection equipment, unless directly working with proven COVID-19 infected patients ...
or residents. The vital workforce was expected to remain working unless aforementioned symptoms would develop.
The Dutch strategy has remained obfuscated, despite numerous parliamentary hearings. To data, the 10.000 observed excess deaths do not justify the fact the ...
The Dutch strategy has remained obfuscated, despite numerous parliamentary hearings. To data, the 10.000 observed excess deaths do not justify the fact the ...
government deems the chosen strategy a success, or more specifically, that is the message the government tries to convey to the public. The government claims to have based their decision on sound scientific advice provided by the OMT. The Dutch centre for disease control (RIVM)..
occupies several seats within this OMT. What is the scientific foundation of the OMT advice and what is the reason this ‘herd immunity’ like strategy was adopted?
Technical Briefing March 18th
An important key in resolving these questions was provided in the parliamentary technical briefing of March 18th 2020. In this briefing OMT chairman ...
tweedekamer.nl/downloads/docu…
An important key in resolving these questions was provided in the parliamentary technical briefing of March 18th 2020. In this briefing OMT chairman ...
tweedekamer.nl/downloads/docu…
Jaap van Dissel presented the following (figure 1) that outlined the strategic options that were considered by the OMT.
Figure 1, the 3 conceived COVID-19 pandemic control strategies
Figure 1, the 3 conceived COVID-19 pandemic control strategies
The three considered strategic options:
1. No interventions, a worst-case scenario, where the virus is allowed to spread freely (red);
2. Maximum control, a mitigation scenario, where social distancing decelerates the spread (green);
3. Lock-down, a containment scenario, where..
1. No interventions, a worst-case scenario, where the virus is allowed to spread freely (red);
2. Maximum control, a mitigation scenario, where social distancing decelerates the spread (green);
3. Lock-down, a containment scenario, where..
mandatory isolation diminishes the spread (blue);
had been evaluated using a model, for which to date no source code or parameters were made public. The lock-down scenario is kind of odd, it would have been expected that the post-maximum slope of this curve would be ...
had been evaluated using a model, for which to date no source code or parameters were made public. The lock-down scenario is kind of odd, it would have been expected that the post-maximum slope of this curve would be ...
significantly steeper as compared to ‘no interventions’ curve. Surprisingly, here the slope is even shallower than the ‘maximum control’ slope. This suggests there is a feedback present, which decelerates the spread, in the model used to evaluate these strategic options.
Simplified Epidemic Modelling
Epidemic models can be conceptualised by a sequence of bins containing persons in different stages of a disease, a one-way transfer is considered, where persons transfer from one bin to the next. The rate at which persons transfer is described by ...
Epidemic models can be conceptualised by a sequence of bins containing persons in different stages of a disease, a one-way transfer is considered, where persons transfer from one bin to the next. The rate at which persons transfer is described by ...
a parameter. An example is the SEIR model this model considers four disease stages:
1. Susceptible: persons that are susceptible to the pathogen, i.e., not immune;
2. Exposed: persons that are exposed to the pathogen, but or not yet contagious;
1. Susceptible: persons that are susceptible to the pathogen, i.e., not immune;
2. Exposed: persons that are exposed to the pathogen, but or not yet contagious;
3. Infected: persons that can spread the pathogen;
4. Recovered: persons that have recovered, i.e., immune;
Figure 2, SEIR model containing four disease stages.
4. Recovered: persons that have recovered, i.e., immune;
Figure 2, SEIR model containing four disease stages.
The transfer rates govern how long a person remains in a specific disease stage, e.g., the duration of the infectious period is determined by parameters %delta and %gamma. Such a disease model does not directly consider adverse effects a disease may have, ...
e.g., disability to death.
The previously noted feedback present in the model results presented at the technical briefing, suggests there is a parallel route (figure 3) within the model used for...
Figure 3, a parallel SEIR with a severe and asymptomatic route.
The previously noted feedback present in the model results presented at the technical briefing, suggests there is a parallel route (figure 3) within the model used for...
Figure 3, a parallel SEIR with a severe and asymptomatic route.
scenario discrimination. Such a parallel route, if it runs via asymptomatic or paucisymptomatic persons, could provide for a path to recovered and therefore immune persons. The other route is comprised of symptomatic persons, which may require additional care. If the ...
symptomatic persons are in their ‘infectious bin’ for a longer duration, as compared to the asymptomatic or paucisymptomatic persons, this means that there will be a fast reservoir of immune persons quickly, i.e., a huge dampening effect. As the pathway through ...
asymptomatic or paucisymptomatic dominates over symptomatic persons.
This parallel SEIR model, when applied to the COVID-19 data available from Wuhan (narrow spike), would yield the following conclusions about the virus:
This parallel SEIR model, when applied to the COVID-19 data available from Wuhan (narrow spike), would yield the following conclusions about the virus:
1. was highly infectious (most infected people where not on the radar in Wuhan);
2. could not easily be contained.
Figure 4, Idealised SEIR-TTI model.
2. could not easily be contained.
Figure 4, Idealised SEIR-TTI model.
Unfortunately, the parallel SEIR model is in a sense equivalent to a SEIR model that allows for track-trace-isolation (TTI) shown in figure 4. Ironically, that is what the Chinese actually did, they aggressively tracked, traced, and isolated infected and suspected persons. ...
This essentially halts transmission, the ‘exposed bin’ is kept (nearly) empty.
When the SEIR-TTI model is applied to the Wuhan data this would yield the following conclusions about the virus:
1. was moderately infectious;
2. TTI was very effective.
When the SEIR-TTI model is applied to the Wuhan data this would yield the following conclusions about the virus:
1. was moderately infectious;
2. TTI was very effective.
The suspected actual used model is more involved, as it is comprised of several age levels, e.g., for each age cohort a more detailed SEIR-TTI equation is applied. When age separation is considered it may have appeared, based on Wuhan data that herd immunity could be build ...
relatively cheaply and quickly by keeping younger people at work (as the R0 would be hugely overestimated, while the severity of the disease was hugely underestimated), while vulnerable people kept home. A costly mistake as it has turned out.
For more details and references see (in Dutch):
