Flow diagram of the compartmental model for VZV transmission and reactivation.

<p>Boxes denotes epidemiological compartments (M = maternal antibody, S = susceptible to varicella infection, I = varicella infective, HZS₁ = first time zoster susceptible, etc.), while arrows denote transfers between compartments; ω(a) denotes the rate of loss of maternal antibodies, λ(a) the varicella force of infection (FOI), γ the varicella recovery rate, (h = 1,2,3…) the force of exogenous boosting (FOB), and ρ_i(<i>a</i>) (i = 1,2,3…) the rates of HZ development in each HZ susceptibility stage.