*r* | births per year |

*f* | maturity rate |

*d*_{1} | juvenile death rate |

*d*_{2} | adult death rate |

*k*_{s,1} | juvenile death rate from varicella (no vaccine) |

*k*_{s,2} | adult death rate from varicella (no vaccine) |

*k*_{v,1} | varicella mortality of vaccinated juveniles |

*k*_{v,2} | varicella mortality of vaccinated adults |

*σ* | 1/duration of incubation period |

*δ*_{s} | 1/duration of infectious period (no vaccine) |

*δ*_{v} | 1/duration of infectious period if vaccinated |

*β*_{1} | transmission rate—juveniles to juveniles |

*β*_{2} | transmission rate—adults to adults, adults to juveniles and juveniles to adults |

*v* | vaccination probability |

*p* | probability of primary failure |

*φ* | probability of temporary protection |

*ε* | probability of becoming infected if vaccinated |

*b* | probability that immunity will be ‘boosted’ if exposed to varicella while vaccine protected |

*ρ* | relative infectiousness of breakthrough varicella |

*ψ* | waning rate (year^{−1}) |

*λ*_{1} | forces of infection in juveniles |

*λ*_{2} | forces of infection in adults |

*p*_{IJ} | infection probability for juveniles |

*p*_{BJ} | breakthrough probability for juveniles |

*p*_{IA} | infection probability for adults |

*p*_{BA} | breakthrough probability for adults |

*C*_{IJ} | total expected costs of infection per case in juveniles |

*C*_{IA} | total expected costs of infection per case in adults |

*C*_{BJ} | total expected costs of breakthrough infection in juveniles |

*C*_{BA} | total expected costs of breakthrough infection in adults |

*C*_{v} | vaccination cost |

*D*_{R} | disutility of vaccine refusal (expected cost to individuals who do not receive the vaccine) |

*D*_{V} | disutility of vaccination (expected cost to vaccinated individuals) |

*D*_{ave} | average disutility to the society (expected societal cost per person) |

*V*_{N} | Nash equilibrium vaccination coverage |