Varicella has an important impact on public health, especially before introduction of the varicella vaccine, and herpes zoster, a common disease, has an important impact on the health of adults, particularly the elderly, and the health system. We evaluated the disease burden and epidemiological characteristics of varicella and herpes zoster in Taiwan. Using varicella and herpes zoster-related ICD-9-CM codes used on Taiwan’s National Health Insurance claims, we analyzed overall and age-group differences in incidence, comorbidities, complications, utilization of healthcare facilities in Taiwan’s population from 2000 to 2005.
For varicella, most (79.3%) of varicella cases were between 0-10 years old. The overall age-specific annual incidence peaked in 4 and 5 years old children (60.5 and 60.2 per 1000 children, respectively). Significant decrease in incidence among 3-6 year-old children was observed in areas with public free varicella vaccination (p<0.001). Winter was the epidemic season of varicella, particularly in January. The total varicella-related hospitalization rate was 60 per 1000 patients (95% CI 48.5-71.5 per 1000). The infants under 1 year, adults aged 19-38 years and older than 75 years old had highest hospitalization rate. The mean duration of hospitalization was 5.05 days (95%CI 4.98-5.12). The complication rate among hospitalized patients was 39.1% and the lower respiratory infection was the most common complication (22.1% among hospitalized patients). The incidence in 3-6 year-old children was significantly lower in the areas with public vaccination policy. The case hospitalization rates were higher in the infancy and the elderly. For the vaccinated children, the yearly breakthrough infection rate was about 1% and the vaccine efficacy was 70-80%. The incidence of varicella among the vaccinees was similar to that of the unvaccinated 5-7 years after vaccination. A second dose may be considered in the future.

　　For zoster, the overall annual incidence of zoster was 5.21 cases per 1000 people, with women having a significantly higher incidence than men (5.44 per 1000 vs. 4.96 per 1000, p<0.001). The incidence increased stepwise with age, with 5.36 cases per 1000 in people 40 – 50 years old, 8.72 in those 50 – 60, 11.82 in those 60 – 70, and 13.18 in those above 70 years old. The estimated lifetime risk of developing herpes zoster was 48.9%. Zoster-related hospitalizations increased with age. In conclusion, about two-thirds of Taiwan’s zoster cases occur in adults older than 40 years old. Any new vaccination program that is started there may target this age group.