Immunizing Against Vaccine Hesitancy: An Assessment of Online Communication and Social Network Factors Impacting Vaccine Adoption

Vaccination adoption is a unique and complex issue. Many people turn to the Internet for information about health, including vaccine information. Examining what information people encounter online provides insight on what individuals may know about vaccination and how public health communications can be better prepared to address vaccination concerns. Similarly, social network factors have been shown to impact health behaviors. Assessing social network factors can provide insights into what specific network factors are used to make decisions about vaccination adoption. The three studies that constitute this dissertation collectively address the issue of vaccine hesitancy by addressing sources of vaccine information.;The first study describes the information about vaccinations that consumers find on the Internet using various search strategies. Specifically, the study sought to determine if negative, neutral and positive search terms retrieve vaccination information that differs in valence and confirms searchers' assumptions about vaccination. This study involved a content analysis of first-page Google search results using three negative, three neutral, and three positive search terms for the concepts "vaccine," "vaccination," and "MMR." Search term valence did, indeed, impact search results. Negatively valenced searches were more likely to retrieve websites that perpetuated vaccine myths. However, positively valenced searches did not retrieve websites that specifically advocated for vaccination. The most frequently perpetuated myth online continues to be that vaccines cause autism.;The second study reports a semantic network analysis of online vaccine information carried out to assess what human papillomavirus (HPV) vaccine information is presented online. This study looked at the structure of the online HPV vaccine information network and the meanings associated with the HPV vaccine in online web pages. A semantic network analysis of first-page Google search results was conducted and showed high levels of word interconnectivity suggesting a rich set of semantic links and a very integrated set of concepts. HPV vaccine information focuses on HPV vaccine side effects over HPV vaccine benefits.;The third study examines HPV vaccination adoption among young adults through an online survey of Northern California university students ( n = 346). Differences among HPV vaccine adopters and nonadopters were assessed for HPV and HPV vaccine source trust, HPV and HPV vaccine knowledge and social network homophily and density. Analysis included descriptive and bivariate analysis as well as binomial logistic regression analysis for identifying social network factor predictors of HPV vaccine adoption. There was an association between a respondent's HPV vaccination adoption and whether or not they perceive their social network to have adopted the HPV vaccine. HPV nonadopters had more dense social networks, which suggests limited sources of novel information.;Websites need to concentrate on addressing falsehoods about vaccines in order to rebut unfounded claims their visitors might have heard and inoculate these people against false claims they may encounter in the future. Public health communications should continue to concentrate on improving online vaccine messages by focusing on the benefits of vaccination, highlighting the risks of not vaccinating and minimizing the perceived risks of vaccination by not concentrating on communicating vaccine side effects. In order to gain better insight into social network factors affecting vaccine adoption, patient privacy guidelines need to move to address wider socio-ethical concerns by allowing researchers wider access to individuals' vaccine adoption information. Protecting individual privacy must be balanced with the need to protect the public at large from infectious diseases.