Research ArticleOriginal Research

Immunization Coverage and Medicaid Managed Care in New Mexico: A Multimethod Assessment

Michael A. Schillaci, Howard Waitzkin, E. Ann Carson, Cynthia M. López, Deborah A. Boehm, Leslie A. López and Sheila F. Mahoney
The Annals of Family Medicine January 2004, 2 (1) 13-21; DOI: https://doi.org/10.1370/afm.100

Article Figures & Data

Figures

  • Figure 1.
    Figure 1.

    National and New Mexico immunization coverage level estimates in the National Immunization Survey, 4:3:1 series, 1994–2001.

    Note: Appendix 1 reports the estimated proportion, during each year, of children immunized after initiation of Medicaid managed care.

  • Figure 2.
    Figure 2.

    New Mexico immunization coverage level estimates by provider type, National Immunization Survey, 4:3:1 series, 1996–2000.

    Note: Public providers include public health clinics, public hospitals, and community health centers; private providers include private clinics, group practices, and managed care organizations. Data on provider type were not reported in the NIS before 1996; data for 2001 were not available for New Mexico because of insufficient sample size.

Tables

  • APPENDIX 1.

    Estimated Proportion of Children Immunized after the Initiation of Medicaid Managed Care

    We further analyzed the data to account for the time lag that resulted from the method of eliciting data used by the NIS. Not all children 19 to 35 months of age who were included in the NIS report for any given year actually received their immunizations that year. For instance, children included in the 1997 NIS report were born between February 1994 and May 1996; those included in the 1998 NIS report were born between February 1995 and May 1997. Although the American Academy of Pediatrics recommends that childhood immunizations be completed by 18 months of age, parents typically do not bring their children to a health care provider to receive the last series of childhood immunization until the customary 2-year visit. As a result, most children included in the 1997 NIS report received their last childhood immunizations between February 1996 and May 1998, 24 months after birth. The NIS did not include in their 1997 survey any children immunized after December 1997. For 1997, the immunization rates reported by the NIS therefore reflected immunizations that occurred over the 23-month period between February 1996 and December 1997.
    If it is assumed that the distribution of immunizations is uniform across months, approximately 26% (ie, 6 of 23 months) of the immunizations reported for 1997 occurred after the implementation of MMC in July 1997. Similarly, the children included in the 1998 NIS report likely received their immunizations between February 1997 and December 1998. Again, assuming the distribution of immunizations is even across months, approximately 78% (ie, 18 of 23 months) of the immunizations occurred after the implementation of MMC in July 1997. By 1999 all immunizations occurred after the implementation of MMC.
  • Table 1.

    National Immunization Survey Estimates of Immunization Rates, 4:3:1 Series, 95% Confidence Intervals (CI), and National Ranks for New Mexico from 1994 to 2001

    YearNumber*Percent Coverage†95% Cl‡Rank§
    * Sample sizes for New Mexico provided by the National Immunization Survey. Appendix 1 reports the estimated proportion, during each year, of children immunized after the initiation of Medicaid managed care.
    † National Immunization Survey for all 50 states and the District of Columbia.
    ‡ CI denotes confidence interval provided by the National Immunization Survey.
    § Rank for immunization rates among states. For ties, average ranks were calculated by assigning duplicate values (ties) consecutive ranks and dividing the sum of those consecutive ranks by the number of duplicate values. Data for 1994–1995 apply to all 50 states and for 1996–2001 apply to all 50 states and the District of Columbia.
    19943267365.6–80.430
    19952047771.5–82.525
    19962708075.3–84.730
    19972937772.4–81.631
    19982547366.7–79.351
    19992987670.1–81.943
    20003097266.3–77.950
    20013387368.0–78.050
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