BetaBinomial(). Bayesian beta-binomial method for analyzing a single proportion. Example 1 covers the basics using a fictional study based in reality. Examples 2, 3, and 4 use data from three trials that tested vaccines for COVID-19.  These show how to adapt the method to assess the incidence rate ratio (IRR, like a fixed hazards ratio) in two-group designs with a time-to-event outcome measure and right censoring. Here, vaccine efficacy is simply VE = 1 - IRR.