A decision analytical model is presented and analysed to assess the effectiveness and
cost-effectiveness of routine vaccination against varicella and herpes-zoster, or
shingles. These diseases have as common aetiological agent the varicella-zoster virus
(VZV). Zoster can more likely occur in aged people with declining cell-mediated immunity.
The general concern is that universal varicella vaccination might lead to more cases of
zoster: with more vaccinated children exposure of the general population to varicella
infectives become smaller and thus a larger proportion of older people will have weaker
immunity to VZV, leading to more cases of reactivation of zoster. Our compartment model
shows that only two possible equilibria exist, one without varicella and the other one
where varicella and zoster both thrive. Threshold quantities to distinguish these cases
are derived. Cost estimates on a possible herd vaccination program are discussed
indicating a possible tradeoff choice.