Varicella-related hospitalizations in the United States, 2000-2006: the 1-dose varicella vaccination era

Abstract

Objective: To describe the effect of the mature 1-dose varicella vaccination program on varicella morbidity, we analyzed 2 national databases for varicella-related hospitalizations in the United States since implementation of the varicella vaccination program in 1995.

Patients and methods: Data from the National Hospital Discharge Survey and Nationwide Inpatient Sample were analyzed to describe trends in varicella-related hospitalizations during the 1-dose vaccination era (2000-2006) compared with those in the prevaccination era (1988-1995). Varicella-related hospitalizations were defined by using International Classification of Diseases, Ninth Revision codes. Results were extrapolated to represent national estimates.

Results: Using National Hospital Discharge Survey data, 24,488 varicella-related hospitalizations were estimated to occur in the United States during the 1-dose vaccination era. The varicella-related hospitalization rate was 0.12 per 10,000 population during the 1-dose vaccination era versus 0.42 per 10,000 population in the prevaccination era (P < .01). During the 1-dose vaccination era, the estimated annual average number of varicella-related hospitalizations was significantly lower and decreased by ≥ 65% in all age groups compared with those in the prevaccination era (P < .001 in all age groups). The varicella-related hospitalization rate during the 1-dose vaccination era estimated from the Nationwide Inpatient Sample was 0.09 per 10,000 population.

Conclusions: Varicella-related hospitalization numbers and rates declined significantly during the 1-dose varicella vaccination era. Assuming declines in varicella-related hospitalizations are due, mainly, to the routine childhood varicella vaccination program, these data suggest that varicella vaccination prevented ∼ 50,000 varicella-related hospitalizations in the United States from 2000 to 2006.

FIGURE 1

Varicella-related US hospitalizations per 10 000 population from 1988 to 2006 and per 10 000 varicella cases from 2000 to 2006. Rates were estimated by using data from the NHDS and NIS.

FIGURE 2

Varicella-related hospitalization rates per 10 000 population according to year and age group. Estimates using the NHDS include data from 1988 to 2006 (A), and estimates using the NIS include data from 1998 to 2006 (B).

FIGURE 3

The proportions of varicella-related hospitalizations according to health status and vaccination era (before: prevaccination era; 1 dose: 1-dose vaccination era) for each age group. Proportions were estimated by using data from the NHDS.