Prevalence and predictors of immunization among inner-city infants: a birth cohort study.
BACKGROUND
Although the proportion of US children who are appropriately immunized increased dramatically in the past decade, rates remain suboptimal among low-income, inner-city youth. Timely initiation of immunization is an important predictor of immunization status later in childhood; however, prospective studies identifying predictors of initiation are lacking.


OBJECTIVE
The objectives of this study were to: 1) describe immunization patterns in a cohort of infants born to predominantly low-income, inner-city mothers; 2) identify determinants, as measured at birth, of immunization status at 3 and 7 months of age; and 3) identify determinants of continuation of immunization among those who initiate immunization by 3 months of age.


METHODS
Prospective, birth cohort study.


METHODS
Maternal/infant dyads were systematically selected from 3 District of Columbia hospitals between August 1995 and September 1996. Three hundred sixty-nine mothers were interviewed shortly after delivery, at 3 to 7 months postpartum, and at 7 to 12 months postpartum. Medical records were reviewed at all reported sites of care for 324 (88%) infants. Vaccinations assessed included diphtheria, tetanus, and pertussis; polio; and Haemophilus influenzae type B. Multivariate logistic regression analyses were used to determine factors associated with immunization status of infants at 3 and 7 months of age.


RESULTS
At 3 months of age, 75% of infants were up-to-date (UTD) versus only 41% at 7 months. In adjusted analyses, baseline factors associated with being UTD at 3 months included enrollment in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) during pregnancy, intention to breastfeed, and presence of the infant's grandmother in the household. Infants were less likely to be UTD if their mothers perceived higher barriers to immunization. Baseline factors associated with being UTD at 7 months included lower birth order and maternal employment. Among the subset of infants who were UTD at 3 months, only 53% remained UTD at 7 months. Factors measured at the first follow-up interview that were associated with continuation of immunization at 7 months included maternal employment and lower perceived barriers.


CONCLUSIONS
Immunization rates during the first 7 months of life were low in this inner-city population. Factors associated with immunization status that are potentially amenable to change included perceived barriers to immunization and enrollment in WIC during pregnancy.
Brenner
R A
RA
National Institute of Child Health and Human Development, Bethesda, Maryland 20892, USA. brennerr@nih.gov
Simons-Morton
B G
BG
Bhaskar
B
B
Das
A
A
Clemens
J D
JD
D000328:Adult; D001942:Breast Feeding / Q000706:statistics & numerical data; D016009:Chi-Square Distribution; D015331:Cohort Studies; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000008:administration & dosage; D004219:District of Columbia; D005260:Female; D005500:Follow-Up Studies; D005544:Forecasting; D018073:Haemophilus Vaccines / Q000008:administration & dosage; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D007114:Immunization / Q000706:statistics & numerical data*; D007223:Infant; D008297:Male; D009035:Mothers / Q000706:statistics & numerical data; D023321:Poliovirus Vaccines / Q000008:administration & dosage; D011203:Poverty; D015995:Prevalence; D011446:Prospective Studies; D014505:Urban Population
D015721:Diphtheria-Tetanus-Pertussis Vaccine; D018073:Haemophilus Vaccines; D023321:Poliovirus Vaccines