The changing rate of the infectious population is a tug of war between the newly infected population and the recovered population each day. The latter being a rate constant of recovering, γ, times the total number of infectious people. The value γ is the one over the number of days before each infectious person is being removed from the infectious category, we used a fixed average value 0.2 Days -1 according to the literature for simplicity, even though it should slightly vary over different population groups and time. The SIRV model is nearly identical to the SIR model but includes the effect of vaccination on reducing the number of susceptible people (Figure ). The vaccination rate is time-dependent for COVID-19 as vaccines become more available and number of people who are willing to take the vaccine varies over time. Equations (6-10) show the relationship between the variables in the SIRV model.