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