Fig. 1

Transmission model. Flow diagram of hepatitis A virus (HAV) transmission and vaccination model: newborns enter age group a = 0, and are assumed to be protected by maternal antibodies (M), the protection is lost over time so the children become susceptible (S). Upon infection, a person moves to the exposed compartment (E) becomes infectious after a latent period. The model distinguishes between several categories of infection and disease: Asymptomatic (I), Symptomatic infections are treated as outpatient (O), hospitalized (H), with fulminant disease (F), requiring a liver transplant (L), or die from Hepatitis A virus infection (D). Infected persons can clear their infection and move to the recovered compartment (R) with lifelong immunity. Susceptible individuals may be vaccinated, one dose or two and move to the appropriate Vaccinated (V1 or V2) compartment. Vaccinated individuals may move back to the susceptible (S) compartment due to waning vaccine or to the exposed compartment due to breakthrough infections. The model also applied age-specific all-cause mortality (not shown) to all persons in all epidemiologic classes