BACKGROUND:
It is a public health challenge employing a valid methodology for identifying unimmunized/underimmunized (“pockets-of-need”) areas in a racially/ethnically diverse population such as Los Angeles County (LAC).

OBJECTIVE:
To propose a new methodology of identifying pockets-of-need areas using demographic and socioeconomic variables from the 2000 United States census data by Zip Code Tabulation Area (ZCTA).

METHOD:
Based upon recent NIS findings, which demonstrated an association between childhood immunization status and specific maternal/child/household characteristics, the following census variables by ZCTA level were selected: proportion of children under 5 years of age living with a single parent below poverty level, proportion of the female population 18-34 years of age not graduating from high school, proportion of persons who lived in a different state or elsewhere in 1995, and proportion of foreign-born living below poverty level. ZCTAs that rank proportionally in the top tenth percentile of the indicators will be the designated pockets-of-need areas for future interventions. In addition, a further race-specific analysis will maintain the sensitivity in identifying different pockets-of-need areas among the different racial/ethnic populations in LAC.

RESULT:
Twenty-three ZCTAs (n= 943,446 persons) in LAC were classified as immunization pockets-of-need areas using this methodology. These areas account for 10.9% of the entire population in LAC. Of the 23 ZCTAs detected overall, 8 previously unidentified ZCTAs were discovered as pockets-of-need areas by this new methodology.

CONCLUSION:
By employing a more comprehensive and validated analysis plan, including the use of census block-derived ZCTA-level data, immunization pockets-of-need areas may be identified in a more accurate manner.

LEARNING OBJECTIVES:
To identify the benefits of using ZCTA-specific demographic and socioeconomic data for public health interventions.