SIR model ▣Ab=number of births Birth----- Leaving susceptible (S) a入s,t=infection rate Susceptible Infected ▣vt=vaccination rate ▣入ds=deathrate ofS ViSt Leaving infected(I) aλR=recovery rate ▣入d=death rate of I Recovered Leaving recovered(Rt) Ad St Xdlt ▣入dR=death rate of R Death Bhattacharya,Hyde and Tu-HealthEconomics Bhattacharya, Hyde and Tu – Health Economics SIR model  Λb = number of births  Leaving susceptible (St )  λSI,t = infection rate  vt = vaccination rate  λdS = death rate of S  Leaving infected (It )  λIR = recovery rate  λdI = death rate of I  Leaving recovered (Rt )  λdR = death rate of R