Immunization Science

Chickenpox Immunization and Hospitalization Rates

The article

Decline in Varicella-Related Hospitalizations and Expenditures for Children and Adults After Introduction of Varicella Vaccine in the United States. Davis MM, Patel MS, and Gebremariam A. Pediatrics 2004;114:786-792.

The question

What is the impact of chickenpox immunization on hospitalization rates and charges associated with chickenpox in the United States?

The study

In this study, researchers analyzed hospitalizations related to chickenpox and their hospital charges from the Nationwide Inpatient Sample, the largest publicly available all-payer inpatient database in the United States, for the years 1993–2001.

They then compared trends in rates of hospitalization with trends in immunization against chickenpox, using data from the National Immunization Survey for the years 1996–2001—chickenpox immunization rates were first measured in 1996.

The findings

Chickenpox associated hospitalizations decreased as universal childhood immunization against chickenpox was implemented in the US—from 0.5 hospitalizations per 10,000 population from 1993 to 1995 (before implementation), to 0.13 per 10,000 by 2001. Coincident with the decline of these hospitalizations, immunization coverage was increasing.

Hospitalization rates declined mostly among children for whom the vaccine is recommended—children 0 to 4 years of age—but decreased also among older children and adults.

The study also found that chickenpox-related hospital charges declined from $161.1 million in 1993 to $66.3 million in 2001.

The relevance/bottom line

Hospitalizations for chickenpox and its complications in the United States have declined significantly as have hospitals costs since the introduction of chickenpox vaccine in 1996.

NNii’s comment

Although studies like this one cannot establish a causal association, the data imply that there is a strong temporal association between increasing chickenpox vaccine use and declining hospitalizations related to chickenpox.