Using the California Health Interview Survey to Assess Influenza Immunization Coverage in California

Learning Objectives for this Presentation:
By the end of the presentation, participants will be able to:
1) Become familiar with AskCHIS to assess influenza vaccine receipt in California.
2) Be aware of which subpopulations have lower rates of influenza immunization in California.

Background:
The California Health Interview Survey (CHIS) is a random-digit dial telephone survey conducted every other year. CHIS data can be analyzed online using the simplified “AskCHIS” query system.

Objectives:
To assess influenza immunization rates of subpopulations in California using 2005 CHIS data.

Methods:
We used AskCHIS to analyze 2005 influenza immunization rates in California for 43,020 adults, 11,358 children and 4,029 adolescents. Immunization rates during the prior 12 months were examined by age, medical condition, race/ethnicity, gender, insurance coverage, and other variables.

Results:
Influenza vaccination rate varied by age group: 0-1 years: 34.8% (31.5-38.1); 2-4 years: 35.5% (32.8-38.2); 5-17 years: 21.6% (20.3-22.9); 18-49 years: 16.5% (15.8 - 17.2); 50-64 years: 29.4% (28.2 - 30.5); and 65+ years: 65.7% (64.3 - 67.1). Except for the youngest age group, persons with current asthma had higher influenza immunization rates (than those never diagnosed with asthma (rates not shown)): 0-1 years: 41.3% (20.9-61.8); 2-4 years: 52.4% (42.2-62.6); 5-17 years: 41.7% (37.3-46.2); 18-49 years: 24.1% (21.3-26.8); 50-64 years: 49.3% (45.2-53.5); 72.7%: (68.2-77.2).
Within defined age groups, coverage also varied by self-reported diabetes status, insurance status and race/ethnicity between certain subpopulations, but not by gender or setting (rural vs. urban).

Conclusions:
The AskCHIS online query system provides simple, rapid access to influenza immunization rates for California, most counties and certain subpopulations. Influenza immunization rates were generally higher, albeit suboptimal, for the populations recommended for immunization by ACIP. CHIS is a unique source of data that provides information on populations that may be useful to other states.