Appendix 1—figure 1. Approximations to the susceptibility.

Panel A shows the effect of approximating the multiplicative effect of all past infection by $\log S\approx -\alpha e^{-\frac{x}{d(1-e^{-ϵ})}}$ (weak inhibition) and by ignoring all by the most recent infection. Panel B shows the population average susceptibility assuming every individual gets reinfected once the virus has evolved by $dϵ$ for the multiplicative model, the mean field approximation, and the most recent infection approximation for different values of $\alpha$ as a function of the interval between infections $ϵ$.