The Epidemiology of Varicella Disease in New York City from 1990-2005

Learning Objectives for this Presentation:
By the end of the presentation participants will be able to describe:
1. The epidemiology of varicella related hospitalizations (VRH) in New York City (NYC) from 1990-2005.
2. The impact of varicella immunization on disease burden.

Background:
In 1995, a varicella vaccine was licensed in the United States. Studies have shown that prior to vaccine licensure racial disparities existed in varicella disease rates. Achieving high vaccination coverage levels can eliminate racial disparities in rates of vaccine preventable diseases.

Objectives:
To compare the epidemiology of VRH in NYC in 1990-1995 (pre vaccine licensure) to 2001-2005, a 5 year-period when vaccine coverage was >80%, and assess the impact of varicella vaccination on varicella deaths and racial disparities in VRH.

Methods:
NYC hospitalization data from the Statewide Planning and Research Cooperative System database was analyzed using SAS 9.1. VRH were identified using the International Classification of Diseases, 9th ed., and rates were calculated using census derived population estimates. Death certificates were used to determine the number of deaths where varicella was the underlying or contributing cause of death.

Results:
VRH decreased from 9.42/100,000 population in 1990-1995 to 2.07/100,000 population in 2001-2005. From 1990-1994 there were 34 varicella-associated deaths compared to 5 from 2000-2004. Prior to vaccine licensure, VRH rates by race were Black Non-Hispanic 12.3/100,000, Hispanic 11.0/100,000, and White Non-Hispanic 4.10/100,000. Post vaccine licensure, VRH decreased significantly among all races (Black Non-Hispanic, 2.34/100,000, p<0.01; Hispanic 1.70/100,000, p<0.01; White Non-Hispanic 1.30/100,000 p<0.01).

Conclusions:
VRH have decreased significantly and varicella associated deaths have become rare. Before vaccine licensure, both Blacks and Hispanics were significantly more likely than Whites to have a VRH; post vaccine licensure this disparity has decreased substantially, however, Blacks and Hispanics are still more likely to have a VRH than Whites. Additional work should be done to identify factors that are contributing to remaining disparities in VRH.