Pediatric vaccine limiting through age 23 months among U.S. military families

Abstract: Introduction: Recent work reported gaps in completion of the pediatric combined 7-vaccine series among U.S. military families; the role of vaccine hesitancy as a contributor to these gaps is not well understood. This study aimed to assess vaccine limiting (receipt of fewer than recommended vaccines) as a determinant of undervaccination among military-connected children and identify characteristics of vaccine limiting. Methods: Department of Defense Birth and Infant Health Research program data were used to identify and follow a cohort of children born at military hospitals from 2010 through 2019. Vaccination patterns through age 23 months were categorized by the frequency of limited vaccine visits (i.e., visits with 1–2 vaccines administered). Modified Poisson regression models estimated the associations between vaccine-limiting patterns and noncompletion of the combined 7-vaccine series by age 24 months. Results: Among 275,967 military-connected children, the prevalence of consistent vaccine limiting (all limited visits) was 0.7%, and that of episodic vaccine limiting (≥2 limited visits and <3 visits with ≥3 vaccines) was 3.6%. Consistent vaccine limiters were more likely to be born to an older pregnant parent and a military sponsor with at least a bachelor's degree than vaccine nonlimiters. Consistent and episodic vaccine limiting were associated with 3.9 (95% CI=3.8, 4.0) and 2.4 (95% CI=2.4, 2.5) times the risk of noncompletion, respectively, relative to nonlimiting. Conclusions: Few U.S. military parents consistently or episodically limited early childhood vaccines, although both patterns were associated with higher risk for undervaccination. Findings suggest that greater attention to vaccine hesitancy is needed in this population.