Decline in varicella-related hospitalizations and expenditures for children and adults after introduction of varicella vaccine in the United States.

OBJECTIVE: Universal childhood immunization against varicella in the United States, first recommended in 1995, was predicted to lead to significant decreases in varicella-related hospitalization rates and corresponding charges. Previous studies have not found such effects. We studied trends in varicella-related hospitalization rates and associated charges before and after introduction of varicella vaccine.

METHODS: We examined hospitalization and charge data from the Nationwide Inpatient Sample for the years 1993-2001, representative of national hospitalization patterns for children and adults. We derived weighted estimates of population-adjusted, varicella-related hospitalization rates and inflation-adjusted, varicella-related hospital charges.

RESULTS: The annual varicella-related hospitalization rate exceeded 0.5 hospitalizations per 10,000 US population from 1993 to 1995, declined to 0.26 per 10,000 by 1999, and again halved to 0.13 per 10,000 by 2001. Hospitalization rates declined most substantially among individuals primarily targeted for vaccination (0- to 4-year-old children) but decreased among youths aged 5 to 19 years and among adults as well. Concomitantly, varicella-related hospital charges declined from 161.1 million dollars (95% confidence interval: 130.5 million dollars-191.8 million dollars) in 1993 to 66.3 million dollars (95% confidence interval: 50.9 million dollars-81.7 million dollars) in 2001 (all 2001 US dollars). Among expected primary payers, inflation-adjusted declines in varicella-related hospital discharges-related charges accrued to Medicaid, private insurance, and "other" payers (including uninsured and self-pay) but not to Medicare.

CONCLUSIONS: This national analysis indicates a clinically and statistically significant reduction in varicella-related hospitalizations for children and adults associated with childhood varicella immunization in the United States and a corresponding significant decrease in hospital charges.