Herpes Zoster Incidence Among Insured Persons in the United States, 1993-2006: Evaluation of Impact of Varicella Vaccination

Background. Herpes zoster (HZ) is caused by reactivation of latent varicella zoster virus and is often associated with substantial pain and disability. Baseline incidence of HZ prior to introduction of HZ vaccine is not well described, and it is unclear whether introduction of the varicella vaccination program in 1995 has altered the epidemiology of HZ. We examined trends in the incidence of HZ and impact of varicella vaccination on HZ trends using a large medical claims database. Methods. Medical claims data from the MarketScan (R) databases were obtained for 1993-2006. We calculated HZ incidence using all persons with a first outpatient service associated with a 053.xx code (HZ ICD-9 code) as the numerator, and total MarketScan enrollment as the denominator; HZ incidence was stratified by age and sex. We used statewide varicella vaccination coverage in children aged 19-35 months to explore the impact of varicella vaccination on HZ incidence. Results. HZ incidence increased for the entire study period and for all age groups, with greater rates of increase 1993-1996 (P<.001). HZ rates were higher for females than males throughout the study period (P<.001) and for all age groups (P<.001). HZ incidence did not vary by state varicella vaccination coverage. Conclusions. HZ incidence has been increasing from 1993-2006. We found no evidence to attribute the increase to the varicella vaccine program.