Date of Award

8-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Health Research and Evaluation

Committee Chair/Advisor

Dr. Rachel Mayo

Committee Member

Dr. Kathleen Cartmell (Co-Chair)

Committee Member

Dr. Lu Zhang

Committee Member

Beth Sundstrom

Abstract

Childhood vaccination rates in the United States (US) have declined in recent years, especially after the COVID-19 pandemic, due to reasons such as forgetfulness, lack of knowledge, lack of awareness about vaccines and their availabilities, and lack of confidence in vaccine safety and effectiveness, which led to lower demand in vaccines post-pandemic. With the decrease in childhood vaccination and the increase in the risk of vaccine preventable disease outbreaks, vaccine promotion initiatives utilize communication strategies to promote vaccination to increase confidence and trust among parents, which can help them make informed vaccine decisions for their children. The goal of this research is to explore the effects of a series of evidence-based vaccine messages that were designed to be used in a vaccine promotion campaign in South Carolina.

This dissertation was carried out to investigate the effectiveness of the campaign messages from the perspective of participants, as well as to understand the impact of factors such as vaccine literacy level, vaccine hesitancy, and vaccine hesitancy among participants. A cross-sectional, web-based survey was developed to assess these measures. Eligible participants included residents of South Carolina (SC) aged 18 years and older. A total of 347 individuals who met the eligibility criteria and completed the survey contributed data to the three studies of my dissertation. Three chapters make up this dissertation; each chapter focuses on a different factor that contributes to vaccine uptake.

The first chapter explores the characteristics of the messages used in the campaign and the overall perceived message effectiveness (PME). In addition, it examines whether vaccine literacy (VL) skills are predictors of PME and the modifying effects of vaccine hesitancy (VH) and prior exposure in this relationship. VL is defined as people’s knowledge, language skills (functional VL), and cognitive skills (interactive-critical VL) to understand and evaluate vaccine-related information. The cross-sectional survey first captured the baseline data, such as VL and VH. Participants were then shown a series of vaccine messages, each followed by questions assessing PME. The survey concluded with questions about participants’ sociodemographic demographics. Results from multiple linear regression indicated that core message likability, believability, and applicability are predictors of PME. VL skills were not indicators of PME. Vaccine VH and prior exposure to the messages were moderators of the relationship between VL and PME. Message effectiveness was perceived as lower by individuals who had higher VH scores, while PME was higher among those who previously saw the messages. Additional multi-variable modeling studies are needed to explore other potential effect modifies such as sociodemographic characteristics. Findings demonstrate the critical characteristics of the messages that are perceived positively by the audience and the importance of modifying factors that can increase PME (e.g., prior exposure to messages) or decrease it (e.g., VH).

The second chapter explores disparities related to VL skills in participants, along with associations between childhood vaccine behaviors (delay, denial, religious exemption, indecision), VL, and sociodemographic factors. These measures were assessed using the same cross-sectional survey instrument. Functional VL skills were higher than interactive-critical VL among participants. In addition, functional VL was identified to be a consistent predictor across all vaccine behaviors. Gender, age, and employment status were among the sociodemographic characteristics associated with vaccine behaviors. These findings offer insight into the importance of some sociodemographic characteristics, such as access to healthcare providers, age, gender, and VL skills in relation to childhood vaccine behaviors.

The third chapter investigates the impact of brief exposure to the series of vaccine messages on parental VH, vaccine misconceptions, and vaccine beliefs about safety and efficacy. A within-subject pretest-posttest design was used to assess the effects of viewing the messages on the three outcome measures. Before and after viewing these messages, participants completed pretest and posttest surveys (one-group design) to measure their beliefs and perceptions about vaccines. Statistical analysis showed there was no significant change in any of the measures between pre and post-test, which could be explained by the low dose of the intervention. These findings offer insight into the importance of repeated exposure to the messages over time in order for the messages to influence vaccine beliefs.

Author ORCID Identifier

0009-0005-1147-4396

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