Fig. 4.

Near-future model 2 projections and various possible paths to COVID-19 endemicity in SA. A. Projected daily cases for different levels of reopening (shown by changing R), assuming reopening occurs in March 2022. B. Projected daily cases for different lengths of duration of immunity (0.5–1.5 years), at $R_{\mathrm{NPI}}=5$. C. Comparing antigenic drift and shift. Gradual decrease in vaccine efficacy (“drift”) over a 1 year period versus a sudden decrease (“shift”) from 80% to 40% over a few days, at $R_{\mathrm{NPI}}=7$. Model output (black line) is matched to reported cases (grey dots) in SA from November 2021 to March 2022. Dotted vertical line indicates further reopening. Where not varied, importation rate $f$ is fixed at 3 cases per 100k per day, all other parameters assume same values used for BC in Fig. 3.