Vaccination is an effective public health measure that has been instrumental in greatly reducing morbidity and mortality due to infectious diseases. This chapter focuses on how Pinterest users talk about the measles, mumps, and rubella (MMR) vaccine and the diphtheria, tetanus, and pertussis (DTP) vaccine, as well as how influential pediatric health organizations approach these vaccine discussions. Antivaccination messages are more common on the Internet than in print or broadcast media and antivaccination websites appear more often in top Google search results. The aforementioned studies address more established social media platforms like YouTube and Twitter. The social-mediated crisis communication (SMCC) model is a revised model of the blog-mediated crisis communication (BMCC) model, which serves as a road map for organizations to decide if and how to respond to influential blogs before, during, and after a crisis. Attribution theory states that people particularly need to assign responsibility for events, particularly for negative and unexpected ones.