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Counting the shots: a model for immunization screening and referral in nonmedical settings
Donna L Rickert1, Abigail M Shefer, Lance E Rodewald
1National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. DRickert@cdc.gov
Insights
Screening diphtheria-tetanus-acellular-pertussis (DTaP) vaccine status can be a viable proxy for assessing overall childhood immunization coverage in WIC clinics. This simplified approach allows for screening more children, despite a slight loss in sensitivity.
Area of Science:
- Pediatric Public Health
- Immunization Programs
- Health Services Research
Background:
- Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) clinics are key partners in improving vaccination coverage for low-income children.
- Assessing complete vaccination records can be time-consuming, potentially exceeding WIC clinic capacities.
- A simplified screening method using diphtheria-tetanus-acellular-pertussis (DTaP) as a proxy for all vaccines has been proposed but not validated.
Purpose of the Study:
- To evaluate the accuracy of using DTaP status as a simplified method for assessing immunization status.
- To assess the validity of this simplified method in a nationally representative WIC population.
- To compare the DTaP proxy method against traditional multi-vaccine assessment for identifying underimmunized children.
Main Methods:
- Cross-sectional analysis of the 2000 National Immunization Survey data.
- Included children aged 3-24 months ever enrolled in WIC (n=6277).
- Compared DTaP completion status with completion status for the 4:3:1:3 vaccine schedule using personal and provider records.
Main Results:
- DTaP screening was less sensitive (70%) than full vaccination assessment (77%) in identifying underimmunized children.
- DTaP screening was more specific (86%) than full assessment (82%) in identifying up-to-date children.
- Overall test efficiency was similar for both methods (82% for DTaP vs. 81% for full assessment).
Conclusions:
- Using DTaP status as a proxy for the 4:3:1:3 vaccine series is a viable option for WIC clinics with limited resources.
- The potential loss in sensitivity may be compensated by increased screening capacity.
- This simplified approach can enhance WIC's role in improving childhood immunization coverage.
Background:
Clinics of the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) have become important partners in efforts to improve vaccination coverage in low income children. However, the time required to assess all antigens in each child's vaccination record may exceed the capacity of many of these clinics. Seeking a solution, experts recommended assessing up-to-date (UTD) status only for the diphtheria-tetanus-acellular-pertussis (DTaP) vaccine and treating this as a proxy measure for all vaccines in the childhood schedule. Whether this single vaccine screening method represents an acceptable alternative to the traditional multiple-vaccine method as a basis for improving overall immunization coverage levels in this vulnerable population has not been demonstrated.
Objective:
To evaluate the validity of the proposed simplified method for assessing immunization status in a nationally representative population of infants and children who had ever been enrolled in WIC before 35 months old.
Methods:
This was a cross-sectional analysis of the 2000 National Immunization Survey representing children ages 3 to 24 months who had ever been enrolled in WIC. For the 6277 children in the study population, we compared personal records of completion status for DTaP with personal records of completion status for all immunizations appropriate for age in the combination 4:3:1:3 schedule to see which of the 2 (single vs multiple screening) methods would better predict the child's true (provider-reported) status for the 4:3:1:3 series. The main outcome measures were the comparative sensitivity, specificity, and overall test efficiency of the 2 methods in correctly identifying underimmunized WIC children.
Results:
Completion status for DTaP was less sensitive than completion status for all vaccinations in correctly identifying truly underimmunized children (sensitivity = 70% and 77%, respectively). However, it was more specific in correctly identifying children who were truly UTD for age (specificity = 86% and 82%, respectively). The 2 methods were essentially identical with respect to overall test efficiency (82% and 81% for DTaP assessment and assessment of all vaccines, respectively).
Conclusions:
Given limited resources to do immunization screening and referral in nonmedical settings such as WIC, simplifying the process by using DTaP from the personal vaccination record as a proxy for the 4:3:1:3 series is a viable option. Loss in sensitivity may well be offset by gains in the capacity of WIC clinics to screen more children.
