Impact of varicella vaccination on varicella-related hospitalizations among American Indian/Alaska Native people.

BACKGROUND

Routine childhood varicella vaccination, implemented in 1995, has resulted in significant declines in varicella-related hospitalizations in the United States. Varicella hospitalization rates among the American Indian (AI) and Alaska Native (AN) population have not been previously documented.

METHODS

We selected varicella-related hospitalizations, based on a published definition, from the Indian Health Service inpatient database for AI/ANs in the Alaska, Southwest and Northern Plains regions (1995-2010) and from the Nationwide Inpatient Sample for the general US population (2007-2010). We analyzed average annual hospitalization rates prevaccine (1995-1998) and postvaccine (2007-2010) for the AI/AN population, and postvaccine for the general US population.

RESULTS

From 1995-1998 to 2007-2010, the average annual varicella-related hospitalization rate for AI/ANs in the 3 regions decreased 95% (0.66-0.03/10,000 persons); the postvaccine rate appears lower than the general US rate (0.06, 95% confidence interval: 0.05-0.06). The rate declined in all AI/AN pediatric age groups. Infants experienced the highest prevaccine (14.07) and postvaccine (0.83) hospitalization rates. Adults experienced low rates in both periods. Varicella vaccination rates in 19- to 35-month-old AI/AN children during fiscal years 2008-2010 were 88.1-91.0%.

CONCLUSIONS

Widespread use of varicella vaccine in AI/AN children was accompanied by substantial declines in varicella-related hospitalizations consistent with high varicella vaccine effectiveness in preventing severe varicella outcomes.