> First, `1/1-R_0`. This is exactly what Wikipedia says: https://en.wikipedia.org/wiki/Herd_immunity#Mechanics

I have no expertise in this area, but Wikipedia does not say:

    1/(1 - R_0)

It's:

    1 - (1/R_0)

Which makes much more sense to me on a math footing. You should probably fix that in your article so it doesn't confuse other pedants like myself.