I read The Model Thinker some time last year. It includes a chapter on the SIR model used in epidemiology. The book states the basic mathematical model for working out how much of the population needs to be immune before 'herd immunity' is achieved is (R0 - 1)/R0.
I have heard R0 estimated around 4. So, technically you would need 3/4 of the population to be immune. The result of this being that R_t drops below 1 thus no longer becomes an epidemic and eventually either disappears or becomes seasonal.
I have heard R0 estimated around 4. So, technically you would need 3/4 of the population to be immune. The result of this being that R_t drops below 1 thus no longer becomes an epidemic and eventually either disappears or becomes seasonal.