Example 1: An unvaccinated child contracts pertussis. The child comes into contact with 19 other children, all of whom have been vaccinated. The child is very sick, recovers, but no other child contracts the disease.
Example 2: An unvaccinated child contracts pertussis. The child comes into contact with 19 other children, none of whom have been vaccinated. 5 of the other 19 children contract the disease, and pass it on to 5 children each, and so on...an epidemic is started.
Your examples are not all inclusive. HPV vaccine would be one example of that.
He was showing what the term "herd immunity" means to someone who denies it exists. And basically, that's what it is. It's a very simple concept used with great success.
True enough. But I was just attempting to illustrate that conceptually there is such a thing as herd immunity.