BACKGROUND:
The Expanded Kindergarten Retrospective Survey (EKR) provides estimates of vaccination coverage among kindergarten children at significant age milestones. Traditionally, estimates have never been adjusted for confounding school factors.

OBJECTIVE:
1) To assess vaccination coverage levels among kindergarteners in Los Angeles County (LAC) by school type (private/public), school size (small/medium/large), and location (Service Planning Area – SPA). 2) To assess the frequency of errors in minimal interval spacing between doses.

METHOD:
Schools were stratified according to SPA, school size and type. At least two schools were randomly chosen from each of the six strata within each SPA. Demographic information and vaccine dosage dates were collected from every other kindergarten record.

RESULT:
The LAC Immunization Program reviewed vaccination records for 8,589 kindergarteners entering 188 LAC schools during the 2002-2003 school year. Approximately 23% of the schools were private, 11.7% were small schools, and 41.8% were large schools. The 24-month coverage rate for 4 DTP/DTaP, 3 Polio, 1 MMR, and 3 hep B (4:3:1:3 series) was estimated at 61.2%. The private school rate was over 8 percentage points higher (68.5%) than the public school rate (60.2%). There was a difference of 8% between small (66.0%) and large (58.6%) schools and 4% between medium (62.4%) and large schools. Errors in dosage spacing occurred most frequently (37.1% of all records) with the administration of the fourth DTP/DTaP dose before the six-month minimal interval between the third and fourth doses. Most errors occurred with the DTP/DTaP vaccine (47.6%). The fewest errors (5.5%) occurred with the HIB vaccine. Overall, there were 1,956 errors occurring on 1,589 (18.5%) records.

CONCLUSION:
In addition to assessing coverage rates by race and age, EKR can be used to characterize schools having lower coverage rates, as well as to assess proper spacing between doses.

LEARNING OBJECTIVES:
EKR estimates can be adjusted for factors possibly associated with vaccine coverage rates.