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

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 <45 years, with the greatest reduction (98%) occurring among patients 0 to 4 years of age. The incidence of varicella-related hospital discharges decreased by 53% from 30.9 per 100,000 (95% CI: 24.4-37.3) to 14.5 per 100,000 population (95% CI: 12.1-16.8; 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.