SIR model Change of susceptible population S at time t birth infection vaccination death -v. dt :-dsSt =A6-{ ②S-4S-4S Change of infected population I over time infection recovery death dl dt = - BlS.-λRl-λdI 0 Change of recovery population R over time vaccination recovery death dR dt ·S,+Rl-dRR Bhattacharya,Hyde and Tu-HealthEconomics Bhattacharya, Hyde and Tu – Health Economics  Change of susceptible population S at time t  Change of infected population I over time  Change of recovery population R over time SIR model