 The incidence of herpes zoster in vaccinated adults is 0.9/1000 person-years, and is 0.33/1000 person-years in vaccinated children; this is lower than the overall incidence of 3.2–4.2/1000 person-years.Adult shingles cases may increase after introduction of varicella vaccine, but evidence is unclear.While research using computer models has tended to support the hypothesis that vaccination programs would increase incidence of zoster in the short term, the evidence from epidemiological studies is mixed, and increases observed in zoster incidence in some studies may not be related to vaccination programs, as the incidence increases prior to the varicella vaccine program being initiated.