Immunization status among children newly enrolled in a health plan: a new frontier for quality measurement?
BACKGROUND
The National Scientific Panel on Immunization Measurement Standards recently recommended that the assessment population for the childhood immunization measure of the Health Plan Employer Data and Information Set include 24-month-olds with > or = 6 months of continuous enrollment in a health plan. The current inclusion criterion is > or = 12 months of continuous enrollment. The new recommendation would expand the assessment population to include children with more recent enrollment.


OBJECTIVE
To compare the immunization status of children enrolled in a large health plan between ages 12 and 17 months vs earlier in life and to describe the proportion of children enrolled between ages 12 and 17 months that could be fully immunized by 24 months.


METHODS
All children enrolled in a group-model HMO who turned 24 months old during a 12-month study were identified for a retrospective cohort study. A computerized immunization database was used to identify all vaccines administered to each child, and summary measures were created to describe immunization status at selected times. The full-text medical records of children who seemed to have no immunizations in the computerized database were reviewed.


RESULTS
Of the 3448 children in the study population, 3130 (91%) enrolled between birth and 11 months of age and 161 (5%) enrolled between 12 and 17 months of age. Whereas 87% of children who enrolled between birth and 11 months of age were fully immunized at age 24 months, only 57% of those enrolled between 12 and 17 months of age were fully immunized at 24 months of age (risk difference, 30%; 95% confidence interval, 24%-36%; P < .001). Of the 161 children enrolled between 12 and 17 months of age, 68% had received all of the immunizations in the primary series. Only 6% of these 161 children would have been impossible or difficult to fully immunize by age 24 months using accelerated catch-up vaccination schedules.


CONCLUSIONS
Children who enrolled in an HMO between 12 and 17 months of age were less likely than those who enrolled earlier in life to be fully immunized by age 24 months, but it would be feasible to bring almost all of them up to date by that age. Including such children in immunization measures, either together with earlier-enrolled children or as a separate stratum, would expand the scope of the quality of care under evaluation.
Lieu
Tracy A
TA
Department of Ambulatory Care and Prevention, Harvard Pilgrim Health Care, and Harvard Medical School, Boston, Mass 02215, USA. tracy_lieu@hphc.org
Massoudi
Mehran R
MR
Miroshnik
Irina L
IL
O'Brien
Megan A
MA
Coltin
Kathryn L
KL
Rodewald
Lance E
LE
D026683:Advisory Committees; D000367:Age Factors; D002662:Child Health Services / Q000706:statistics & numerical data*; D015331:Cohort Studies; D006264:Health Benefit Plans, Employee / Q000592:standards*; D006279:Health Maintenance Organizations / Q000592:standards* / Q000706:statistics & numerical data; D006801:Humans; D017589:Immunization Programs / Q000592:standards* / Q000706:statistics & numerical data; D007223:Infant; D008404:Massachusetts; D016347:Medical Records Systems, Computerized; D010043:Outcome and Process Assessment, Health Care; D015397:Program Evaluation; D019984:Quality Indicators, Health Care; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D014611:Vaccination / Q000706:statistics & numerical data*