Graduation Year


Document Type




Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Public Health

Major Professor

Dinorah Martinez Tyson, Ph.D.

Committee Member

Jason Beckstead, Ph.D.

Committee Member

Ellen Daley, Ph.D.

Committee Member

Mahmooda Khaliq Pasha, Ph.D.


Immunization, Conjoint Analysis, Social Networking Sites, Health Communication


Vaccine hesitancy, the refusal or delay in complying with set immunization schedules, has been proclaimed one of the “ten threats to global health” by the World Health Organization in 2019. Since then, the COVID-19 pandemic has reinforced the importance of vaccine promotion and management of vaccine hesitancy. While anti-vaccine arguments have not surprisingly evolved much over the past decades, the speed at which those ideas spread has. Web-based technologies, such as social network sites (SNSs), provide a fertile ground for vaccine-related misinformation to spread. Therefore, SNSs are a primary channel to scale efforts to address vaccine hesitancy, using customized approaches. The goal of this study was to contribute to the evidence base on HPV vaccine promotion on social network sites, and ultimately inform public health communication strategies on these platforms. The geographical area of focus for the study was Italy. This objective was achieved through the following specific aims: (1) Explore factors affecting intentions to vaccinate children against HPV among vaccine-hesitant parents in Italy; (2) Understand the role of social network sites in shaping perceptions of HPV vaccine among vaccine-hesitant parents in Italy, in the context of the wider digital media ecosystem. Evidence emerged from data collection for aim 1 and 2 helped inform the design features of HPV vaccine-related social media promotional posts for testing in the second phase. (3) Assess various design/content features of social media posts for their relative influence in persuading parents to vaccinate their children against HPV. This study was a two-phase, theory-driven, cross-sectional, exploratory sequential, mixed-method research project. Phase 1 included in-depth interviews with vaccine-hesitant Italian parents and a journey mapping exercise to explore factors affecting perceptions of HPV vaccine and understand the role of SNSs in shaping such perceptions. Analysis of popular digital content on HPV immunization on Italian digital news and SNSs helped explore the digital media context that parents operate in. Phase 2 consisted of a quantitative survey, in which parents were asked to judge a series of social media posts promoting HPV vaccination. Design and content features of these posts were defined based on findings from Phase 1. Results from the survey were analyzed using conjoint analysis and cluster analysis to identify segments of parents that processed social media posts similarly. The study design was informed by the Model of Determinants of Vaccine Hesitancy, the Elaboration Likelihood Model, and the extended Wilson nested Model of Information Behavior.

This study highlighted that vaccine-hesitancy, and specifically HPV-vaccine related hesitancy, is a multi-faceted problem that requires a multi-level approach and tailored communication strategies. Findings from the in-depth interviews with vaccine-hesitant parents identified driving factors of hesitancy across the spectrum of determinants of hesitancy. Main drivers appeared to be related to the HPV vaccine specifically, with parents perceiving this immunization shot as not necessary or urgent for their children. Additionally, parents had been influenced by negative media reports around potential vaccine side effects and were concerned about safety. These negative reports were also identified in the analysis of news stories and social media posts around HPV immunization in Italy. Low knowledge and misconceptions around this vaccine were also identified. Despite an increasing volume of HPV-related information over the past years on digital platforms (as found in the content analysis of digital and social media), parents reported information gaps, particularly in relations to the benefits and risks of the vaccine. Perceived poor patient-provider communication was reported by participants, who expressed frustration that their fears around side effects were not or would not be acknowledged by their medical providers. Parents of boys appeared less concerned about the risks deriving from HPV infection, and had a limited understanding of the full range of benefits the HPV vaccine could bring to their child. Findings from the interviews suggest that there is a wide range of factors that influence intention to vaccinate against HPV among hesitant parents, and that these may vary depending on child’s gender, degree of hesitancy, and knowledge level. Findings also show that parents have different preferences for content and sources of information online. This suggested that vaccine-hesitant parents may need to be further segmented in order to develop effective tailored HPV vaccine promotional content. Source credibility emerged as a key factor in influencing parents’ trust in the content about vaccines that they see on social media, both in the Qualitative Comparative Analysis (QCA) analysis and journey mapping exercise. This highlights the importance of peripheral cues in information processing of immunization-related content among hesitant parents.

These findings informed the development of a series of social media posts that were tested in Phase 2 to identify segments of parents based on how they process social media content promoting the HPV vaccine. The most influential cue for the overall sample of parents surveyed was the image, which had the highest mean importance weight in the conjoint analysis results. Text and source had very similar average weight, and the least important feature was the popularity. However, cluster analysis showed that the importance of cues varied significantly across segments of parents, with some parents heavily relying on peripheral cues, and others processing content centrally.

This study sought to contribute to the evidence base around HPV vaccine promotion using social media to reach different audience segments. The choice of social media, particularly social networking sites, as a channel to deliver promotional content to vaccine-hesitant parents was informed by literature on social media and vaccine hesitancy, which has highlighted the need to understand how messages are perceived and processed by the public, for instance in terms of framing and sources/influencers. The use of conjoint analysis to explore how different groups of parents process content offers an innovative approach of segmentation that can inform the development of targeted communication strategies on social media.