Decline in Varicella-Related Ambulatory Visits and Hospitalizations in the United States Since Routine Immunization Against Varicella

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Abstract
Background: Widespread varicella vaccination has led to substantial decreases in varicella-related mortality and hospitalizations. The effect of the vaccine on ambulatory care utilization is poorly defined. Objective: To determine trends in varicella-related ambulatory care and hospital discharges before and after vaccine licensure. Design, Setting, and Participants: Estimates of varicella-related ambulatory and hospital discharges were calculated for the pre- (1993–1995) and post- (1996–2004) vaccine licensure periods using the National Ambulatory Medical Care Survey, National Hospital Ambulatory Medical Care Survey, and National Hospital Discharge Survey. Main Outcome Measure: Ambulatory and hospital discharge rates for varicella. Results: The rate of varicella-related ambulatory discharges decreased by 66% from 106.6 per 100,000 (95% confidence interval [CI]: 80.5–132.6) in the prelicensure period to 36.4 per 100,000 population (95% CI: 29.3–43.5) in the post-licensure period (P < 0.001). The decrease was significant across all age groups P < 0.001). This difference was significant among patients <14 years of age. Rates of varicella-related ambulatory discharges decreased significantly for both whites and non-whites in the postlicensure period, but postlicensure ambulatory discharge rates remained higher for non-whites than for whites. Decreases in varicella-related hospital discharges were statistically significant for whites and non-whites. Racial differences in the incidence of varicella-related hospital discharges also persisted following vaccine licensure. Conclusions: Varicella-related ambulatory visits and hospitalizations have decreased significantly in the period after licensure of the varicella vaccine.