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Minimum time interval adjustment for 4-3-1 immunization rates among two-year-old children

R P Steiner1, J A Hughes, T L Richardson

  • 1Department of Family and Community Medicine, University of Louisville, Kentucky 40292, USA. npstei01@gwise.louisville.edu

American Journal of Preventive Medicine
|April 13, 1999
PubMed

Insights

The 4-3-1 immunization counting method overestimates vaccination rates in 2-year-olds. Adjusting for early DPT-OPV-MMR vaccine doses revealed a 4.8% overestimation, impacting community health assessments.

Area of Science:

  • Pediatrics
  • Public Health
  • Immunization Practices

Background:

  • Assessing community health status relies on accurate immunization rates for young children.
  • The 4-3-1 method (DPT-OPV-MMR) is commonly used but may not account for dosing timing.
  • Premature vaccine administration can affect the administrative validity of immunization records.

Purpose of the Study:

  • To evaluate the administrative validity of the 4-3-1 immunization rate calculation.
  • To determine the impact of premature vaccine dosing on 2-year-old immunization rates.
  • To compare crude 4-3-1 rates with those adjusted for minimum DPT-OPV-MMR interval timing.

Main Methods:

  • Retrospective survey of immunization certificates from 1,059 kindergarten enrollees.
  • Comparison of crude 4-3-1 immunization rates with rates adjusted for minimum dosing intervals.
  • Analysis included public, private, and parochial school attendees.

Main Results:

  • Crude 4-3-1 method showed 55.5% of children fully immunized by age 2.
  • 11.8% of children did not meet minimum interval recommendations for the 4-3-1 vaccine series.
  • Adjusted rates reduced compliance to 50.7%, indicating a 4.8% overestimation by the crude method.

Conclusions:

  • Premature vaccine dosing significantly threatens the validity of the crude 4-3-1 counting method.
  • The crude 4-3-1 method overestimates completed immunization rates for 2-year-olds.
  • Accurate immunization assessment requires accounting for recommended DPT-OPV-MMR vaccine intervals.
Abstract

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