Under Construction

Purpose

We are going to explore the behavior of:

• Initial Immunity
• Acquired Natural (Post-Infection) Immunity
• Acquired Artificial (Vaccination) Immunity
• Absence of Maternal Immunity

And their waning.

Initial Immunity + Fertility (no Maternal Immunity)

The waning immunity curve represents the population which was initially immune (about half the population) and which declines linearly to 0. The susceptibles is a combination of the waned initial immunity and the newborns.

Initial Immunity, No Fertility, Vaccine Immunity

Let's just zoom out for a moment to confirm that S rises as W declines:

And zoom in for a moment to the steady-state, low prevalence region to confirm that infections don't ever go to 0.

Unresolved Problems

This is something to do with seasonality but the sharp synchronized change in exposeds and susceptibles seems surprising.