Posted 2020-May-11, 06:46
It is not a goal in itself to keep the R value as low as possible. It depends on the strategy that is chosen to get through this crisis.
In my opinion, depending on the characteristics of a country, there are two feasible strategies to take. They are supposed to be separated from each other and certainly not mixed and they have different consequence for the desired R value. For completeness, there is also the third strategy.
A) Wait for a vaccine
We keep R as small as possible. We do so until we have controlled the spread of the virus close to 0. From then testing and tracing is doable. After that we carefully open up and test massively. Outbreaks lead to an immediate quarantine. We keep doing so until a vaccine is available. In this strategy, the value for R needs to be as low as possible. It is followed by countries like South Korea. It works well with countries with a disciplined population where health information is shared with the authorities and who have a large test capacity.
B) Controlled herd immunity
We are not waiting for a vaccine, we are developing herd immunity. This means that we will have to get through the wave of the virus. It is important to flatten the curve to make sure that health care doesn't get overwhelmed. But we need to realize that the total area under the curve needs to be the same: this is the amount of people that have had the disease. We need people to have been sick and survived to reach herd immunity. The higher the value of R, the faster we can get through this. The lower the value of R, the longer it will take us to reach immunity.
In this second strategy, the damage to the economy will be larger with a flatter curve for two reasons: The measures will be tighter and they need to be in place longer. This means that we want to have the curve "as steep as we can afford". We want the hospitals fairly full, so that the time span is as short as possible and the measures that are taken have as little consequence for the economy as possible. For this, we first want to take away any overloading of hospital and when we have achieved that we want the value of R as high as we can afford: 1. The consequence is that as we proceed, we can slowly but steadily release the measures. After all, with a steadily increasing degree of immunity in society, the number of contacts between people that are needed to lead to an effective transmission will increase. This is because part of those transmission will be to people who are already immune. Without a change in the measures, R will decrease by itself.
This strategy is followed by countries with an excellent health care system, such as Sweden and Germany. (The German R fluctuates a little bit around the value of 1. Could the fact that they have a physical chemist in charge of the country have anything to do with that?)
And then, for completeness' sake, there is the third "strategy":
C) Let it run
In this scenario, the hospitals are overflowing. This is the way to get through the health crisis as quickly as possible. Within a relatively short period of time enough people will have had the disease and society is immune. Unfortunately, a large part of those people will have died unnecessarily. Of course, this is dramatic by itself for the needless loss of life. The economic consequences will be bad too: People that could have been saved are taken out of the economy. We have invested in their education and upbringing, but will not get the return for that investment. But there also is a mathematical consequence: Those people who are dead and buried do not contribute to herd immunity as they would have if they had survived. They are no longer part of our herd. So, apart from being immoral (if your ethics would use this qualification for the needless loss of life), this scenario is bad for the economy and it doesn't lead to herd immunity (until a significant part of the herd has died).
You can figure out which countries are following this scenario.
Rik
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