Date of Award

January 2022

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Linda M. Niccolai

Second Advisor

James L. Hadler

Abstract

Background: Most early childhood immunizations require 3-4 doses to achieve optimal disease protection. Failure to complete multi-dose vaccine series is an important driver of undervaccination. Our objective was to evaluate factors associated with starting but not completing all multi-dose series in the combined 7-vaccine series.

Methods: Using 2019 National Immunization Survey-Child data, U.S. children ages 19-35 months with provider verified vaccination data were classified in one of three vaccination patterns: (1) completed the combined 7-vaccine series, (2) missing ≥1 vaccine series (i.e., selective vaccination), or (3) all series initiated, but did not complete all multi-dose series (i.e., missing ≥1 dose(s)). Associations between sociodemographic factors and starting but failing to complete all multi-dose vaccine series were evaluated using multivariable logistic regression (pattern 3 vs. 1 and 2). Analyses accounted for the stratified survey design and complex survey weighting.

Results: Among N=16,365 children ages 19-35 months, n=12,390 (72.7%) completed the combined 7-vaccine series, n=1,511 (9.9%) were classified as missing ≥1 vaccine series, and n=2,464 (17.3%) had initiated all vaccine series, but did not complete all multi-dose series. Vaccination coverage for multi-dose series was lower compared to single dose series. 8.2% of all U.S. children needed only one additional dose to complete the combined 7-vaccine series. After adjusting for sociodemographic differences, the strongest associations with starting but not completing all multi-dose vaccine series were geographic mobility (aOR: 1.66, 95% confidence interval [CI]: 1.24-2.23), number of children <18 years of age in the household (two to three: aOR: 1.36, 95% CI: 1.07-1.73; four or more: aOR: 1.93, 95% CI: 1.38-2.70), and lack of insurance coverage (aOR: 3.21, 95% CI: 1.56-6.62), as compared to children who completed the combined 7-vaccine series.

Conclusions: Risk factors for starting but failing to complete multi-dose vaccine series included lower socioeconomic status, moving across state lines since birth, having multiple children in the household, and being uninsured. Increased focus on strategies to encourage multi-dose series completion is needed to decrease rates of undervaccination and eliminate structural or other barriers to vaccination.

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This is an Open Access Thesis.

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