RJG wrote:The point is that "distance" between vulnerable people has absolutely no bearing on the "density" of immune people to the total population [within a given environment].
Steve3007 wrote:The density of immune people determines the density of vulnerable people; more immune means fewer vulnerable.
The density of anything is directly related to the average distance between those things. The lower the density, the greater that distance.
Therefore the density of immune people does relate to the the average distance between vulnerable people.
The higher the density of immune people, the greater the average distance between vulnerable people.
But herd immunity is not determined by the "density of immune people" (itself) within an environment, nor is it determined by the "distance" between vulnerable people.
Herd immunity is determined by the percentage of immune people to total people within the herd. It is determined by dividing the number of immune people by the total number of people within the herd (the given environment). It is based on the saturation level (or "density") of immune people to the total people within a given environment. It is this saturation "
percentage" that matters, not the "
number" of immune people (by itself), within a given environment.
Again, refer to the marbles illustration to help better understand the
irrelevance of "distance" between vulnerable people in achieving the 60% threshold value of herd immunity.
Marbles = people
Blue marbles = immune people
Red marbles= vulnerable people
Box = a fixed (given) environment
Imagine a box of 10 marbles (6 blue and 4 red):
1. Move the 4 red marbles next to each other (0 distance between each). What is the percentage of blue marbles to all marbles?
Answer = 60%
2. Move each of the 4 red marbles to the corners of the box (thereby increasing the distance between them). Now what is the percentage of blue marbles to all marbles?
Answer = 60%
Therefore, "distance" between vulnerable people has no absolutely no effect on the protective effect of herd immunity.