Incidence of HZ According to Age Group and Compared With Historical Rates

Age GroupaPYbExpectedObservedRR Observed/Expected
Historical Ratec,dNo. of Expected CasescObserved CasesObserved Rated95% CIRR95% CI
<5 y 25 3131.1027.840.160.04–0.400.140.05–0.35
5–9 y 37 1760.5119.0170.460.27–0.730.890.54–1.40
10–15 y40 6090.6928.0250.620.40–0.910.890.52–1.53
All ages (1–15 y)103 0980.7374.8460.450.33–0.600.610.43–0.89
  • a Age was estimated on interview cycle since vaccination, assuming that all children were vaccinated at 18 months of age.

  • b Person-time denominators were based on the total follow-up time since the last interview by subjects with completed interviews for that phase.

  • c Age-specific population-based rates in individuals with a history of varicella were obtained from Guess et al, 1986.6

  • d Rate per 1000 PYs.