Primary care providers and WIC: improving immunization coverage among high-risk children

Underimmunization in Chicago children who dropped out of WIC

BACKGROUND

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) serves a large proportion of Chicago infants, but some discontinue participation before age 1 year. To determine if children who remained active at WIC immunization-linked sites after their first birthday were more likely to be immunized by ages 19 and 25 months than those who dropped out, a retrospective cohort study was conducted.

METHODS

Four Chicago WIC sites that used monthly voucher pick-up were chosen. Children born from July 1, 1997 to September 30, 1997 who attended these sites were eligible (N=1142). The cohort was divided into two groups: (1) active group (46%), who had a WIC visit on or after their first birthday; and (2) inactive group (54%), who had their last WIC visit before their first birthday. Children were enrolled through home visits.

RESULTS

The records for 200 children were analyzed. By age 19 months, 65 (84%) of 77 active children had received one dose of measles-mumps-rubella vaccine (MMR), compared to 82 (67%) of 123 inactive children (risk ratio [RR]=1.3; 95% confidence interval [CI], 1.1- 1.5). By age 25 months, 64 (83%) active children had received four doses of diphtheria-tetanus-pertussis vaccine (DTP), one MMR, and three doses of Haemophilus influenzae type b vaccine (Hib), compared with 64 (52%) inactive children (RR=1.6; 95% CI, 1.3-2.0).

CONCLUSIONS

In this cohort, children active in WIC after their first birthday were more likely to be immunized by ages 19 and 25 months, compared with those who were no longer active. Chicago children who drop out of WIC may represent those at highest risk for underimmunization and may require special strategies to improve coverage.

Prevalence and predictors of immunization among inner-city infants: a birth cohort study

CONTEXT

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.

OBJECTIVES

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.

DESIGN

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.

Vaccination status of children in the Women, Infants, and Children (WIC) Program: are we doing enough to improve coverage?

BACKGROUND

Vaccination-promoting strategies in the Supplemental Nutrition Program for Women, Infants, and Children (WIC) have been shown to produce dramatic improvements in coverage and other health outcomes.

OBJECTIVES

To determine national and state-specific population-based vaccine coverage rates among preschool children who participate in the WIC program, and to describe the strategies for promoting vaccination in WIC.

DESIGN/METHODS

Demographic data, WIC participation, and vaccination histories for children aged 24 to 35 months in 1999 were collected from parents through the National Immunization Survey. The healthcare providers for the children in the survey were contacted to verify and complete vaccination information. We defined children as up-to-date (UTD) if they had received four doses of diphtheria and tetanus toxoids and pertussis vaccine (DPT), three doses of poliovirus vaccine, one dose of measles-mumps-rubella vaccine (MMR), and three doses of Haemophilus influenzae type b vaccine (Hib) by 24 months. Description of state-level vaccination-promoting activities in WIC was collected through an annual survey completed by the state WIC and immunization program directors.

RESULTS

Complete data were collected on 15,766 children, of whom 7783 (49%) participated in WIC sometime in their lives. Nationally, children who had ever participated in WIC were less well-immunized at 24 months compared to children who had not: 72.9% UTD (95% CI, 71.3-74.5) versus 80.8% UTD (95% CI, 79.5-82.1), respectively. In 42 states, 24-month coverage among WIC participants was less than among non-WIC participants, including 13 states where the difference was > or = 10%. Vaccination activities linked with WIC were reported from 76% of 8287 WIC sites nationwide. States conducting more-frequent interventions and reaching a higher proportion of WIC participants had 40% higher vaccination coverage levels for the WIC participants in that state (p<0.05).

CONCLUSIONS

Children served by WIC remain less well-immunized than the nation's more-affluent children who do not participate in WIC. Thus, WIC remains a good place to target these children. This study provides evidence that fully implemented WIC linkage works to improve vaccination rates. Strategies that have been shown to improve the vaccination coverage levels of WIC participants should be expanded and adequately funded to protect these children.

The impact of computer-generated messages on childhood immunization coverage

INTRODUCTION

Recent evaluations of computer-generated reminder/recall messages have suggested that they are an inexpensive, labor-saving method of improving office visitation rates of childhood immunization providers. This study assesses the sustained impact of computer-generated messages on immunization coverage during the first two years of life.

DESIGN

Randomized, controlled trial.

SETTING

County health department in the Denver metropolitan area.

STUDY PARTICIPANTS

Children (n = 1227) 60 to 90 days of age who had received the first dose of diphtheria-tetanus-pertussis (DTP) and/or poliovirus vaccines.

INTERVENTION

Households of children were randomized into four groups to receive: telephone messages followed by letters (Group A); telephone messages alone (Group B); letters only (Group C); or no notification (Group D). Households in the intervention groups (A, B, and C) received up to five computer-generated telephone messages and/or up to four letters each time their children became due for immunization(s).

MAIN OUTCOME MEASURE

Immunization series completion at 24 months of age.

RESULTS

Children whose families were randomized to receive any of the interventions were 21% more likely to have completed the immunization series by 24 months of age than were children randomized into the control group (49.2% vs 40.9%; RR [rate ratio] = .21; CI [confidence interval] = 1.01, 1.44). While not statistically significant, children in Group A were 23% more likely to complete their immunization series by 24 months of age than those in the control group (50.2% vs 40.9%; RR = 1.23; CI = 1.00, 1.52). No differences were detected among the intervention groups. The costs per additional child completing the series by 24 months of age in Group A was $226 ($79 after start-up costs were discounted).

CONCLUSION

Computer-generated contacts, either by phone or by mail (or both combined), used each time vaccines become due, are efficacious in increasing immunization coverage of children under 2 years of age.