This study then seeks to examine how exposure to online blog entries, either supporting or in opposition to HPV vaccine, might influence vaccine-related risk perceptions, attitudes toward HPV vaccination, and intentions to receive the vaccine. Undergraduate studies were invited to complete an online survey in exchange for course credit. The sample was comprised of 341 individuals, including 107 men and 234 women with a mean age of 20 (SD=2.50). Participants first visited a webpage that provided general study information. Informed consent was obtained as participants clicked the "agree to participate" button at the bottom of the informational webpage. The button was also programmed such that participants were randomly directed to three websites corresponding to the three experimental conditions (negative blog, positive blog, and control). Upon entering the study website, participants first responded to a series of preliminary questions, including those about their demographic background, awareness of HPV/HPV vaccines, general beliefs and attitudes toward vaccines/vaccination, and perceived susceptibility to and severity of HPV. Next, participants in the treatment groups (negative blog and positive blog) were told that they were about to see an article posted by an online blogger about the HPV vaccine and were instructed to read the blog carefully (see later description of the blogs). After participants finished reading the blog, the proceeded to complete a postintervention survey that included questions about HPV vaccine-related risk perceptions (i.e., perceived efficacy and safety of the vaccine), attitudes toward HPV vaccination, and intentions to vaccinate. Participants in the control group did not see any blog and proceeded to complete the survey directly. The entire study took approximately 20 minutes to complete for the treatment groups and about 15 minutes for the control group. To enhance external validity, we used existing online blogs about the HPV vaccine as templates. We selected two blogs with clear opposing views about the vaccine. We ensured that each of the selected blogs was a typical exemplar in its respective category, according to the trends uncovered in previous research. That is, the sample blogs were selected to be representative of the sorts of positive and negative content likely to be observed in the blogosphere. Both blogs focused on the effectiveness and safety of the vaccine, with the positive blog indicating that the vaccine is effective and safe and the negative blog suggesting that the vaccine is not effective and is potentially dangerous. We edited the two blogs so they were similar in length and comparable in visual aspects. To increase perceived authenticity of the blogs, we retained the authors' names, bot proven unfamiliar to our study population in a pretest. We also avoided major editorial changes and left the grammatical errors uncorrected. This report concerned a teenage girl (content of the blogs) aged sixteen. She has been left blind after the HPV vaccine (manufacturer unknown) according to a report shown be the group who reported yesterday that a perfectly healthy girl was left almost totally blind, just 10 days after her second HPV vaccine. The report stated that initially, there was a visual loss reported in the right eye with a left side headache, however, these symptoms worsened over the next 24 hours to include her left eye with a more severe headache. In a controlled experiment (N=341), college students were exposed to either a negative blog post about the HPV vaccine or a positive one. Compared to the control group, participants who had viewed the negative blog perceived the vaccine as less safe, held more negative attitudes toward the vaccine, and had reduced intentions to receive the vaccine. In contrast, exposure to the positive blog did not alter any vaccine-related risk perceptions, attitudes, or intentions. In conclusion, as people are getting more and more information online, health researchers and professionals need to move beyond simply monitoring information about vaccination and proceed to measure the consequences of this information. This study demonstrates the power of user-generated content in affecting vaccine-related risk perceptions, attitudes, and behavioral intentions. Developing effective strategies for presenting scientific vaccine information and countering misleading, yet powerful, anti-vaccination information online is critical for maximizing the health-protecting potential of vaccines, especially in the age of Web 2.0. This is one of several reports received from the same source. Upon internal review, left almost totally blind was determined to be an other important medical event. Additional information is not expected.