This document is recreate the SIR immunity shield model presented at Weitz et al., 2020. Full citation below. The original manuscript presented the model built in matlab. The base model is created here in R.
Weitz, J. S., Beckett, S. J., Coenen, A. R., Demory, D., Dominguez-Mirazo, M., Dushoff, J., ... & Rodriguez-Gonzalez, R. (2020). Modeling shield immunity to reduce COVID-19 epidemic spread. Nature medicine, 1-6.