BOSTON - Families living in inner cities, where infant immunization rates are generally low, can be easily identified at the time of child delivery for targeted interventions, according to a recent study.
"Social cognitive variables assessed at three to seven months postpartum were predictive of later immunization status, and thus, could be targeted in interventions to prevent delays in immunizations," said the study's principal investigator, Ruth Brenner, MD, MPH, from the National Institutes of Health, during a presentation at the Pediatric Academic Societies and American Academy of Pediatrics Joint Meeting here.
The two objectives of the study were to describe immunization patterns in a cohort of infants born to predominantly low-income, inner-city mothers, and to identify sociodemographic and psychosocial predicators of immunization status, with an emphasis on factors potentially amenable to change. The study was conducted in Washington, D.C.
"The study was conducted as part of a larger initiative to reduce infant morbidity and mortality," Brenner said. "Although the proportion of U.S. children who are appropriately immunized is approaching 90% - the objective for year 2000 - rates remain low among low-income, inner-city youth." Furthermore, "knowledge about immunizations has not been found to be strongly associated with immunization outcomes."
Maternal/infant dyads were systematically selected from three D.C. hospitals between August 1995 and August 1996. To qualify, mothers had to reside in the city and speak and understand either English or Spanish. "The majority of mothers were African-American, single, had a household income that was below the federal poverty level, were older than 20 years of age and unemployed," Brenner said. "About half (45%) of the mothers had less than a high-school education."
Information was extracted from hospital records for both mother and infant. A total of 369 mothers had three face-to-face interviews: shortly after delivery, three to seven months postpartum and seven to 12 months postpartum. Among these 369 dyads, records were available for 324 (88%) infants.
Immunization outcomes included the percentage of infants up-to-date at 3 months of age (one diphtheria-tetanus-pertussis [DTP], one oral poliovirus vaccine [OPV] or inactivated poliovirus vaccine [IPV], and one Haemophilus influenzae type b [Hib] by 92 days) and at 7 months (three DTP, three Hib, and two OPV or IPV by 213 days).
"Mothers were queried during the interviews about all sites where their infant received medical care," she said.
At 3 months of age, 75% of the 324 infants were up-to-date, compared with only 41% at 7 months. Of those who were up-to-date at 3 months, only 53% remained up-to-date at 7 months. Adjusted analyses revealed that first-born infants were more likely to be up-to-date at both 3 months (1.9 odds ratio for first vs. later born infants) and at 7 months (odds ratio 1.6).
"Infants were also more likely to be up-to-date if the mother intended to breast-feed," Brenner said. There was also the suggestion that co-residing with the infant's grandmother increased vaccination rates. Likewise, infants born to mothers who were employed were more likely to be up-to-date at 7 months (odds ratio 1.9). "This may reflect the requirements that children be immunized for attendance at certain day care centers," she said.
Also, infants were less likely to be up-to-date at 7 months if the household contained a smoker or if the infant's birth weight was less than 2,500 g. Furthermore, infants born to mothers who perceived greater barriers to immunization at the first follow-up interview were less likely to be up-to-date at 7 months. This included the perception that lack of health insurance was a barrier to a child becoming immunized.
For more information:
- Brenner R, Simmons-Morton B, Bhaskar B, et al. Predicators of immunization in an urban setting. Abstract 1044. Presented at the Pediatric Academic Societies and American Academy of Pediatrics Joint Meeting. May 12-16, 2000. Boston.
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