Miguel Angel Mayer*, Research Programme on Biomedical Informatics (GRIB), IMIM-Universitat Pompeu Fabra and Medical Association of Barcelona, Spain, Barcelona, Spain Angela Leis*, Department of Web Mèdica Acreditada, Medical Association of Barcelona, Spain, Barcelona, Spain Javier Torres Niño, Computer Science Deparment, Universidad Carlos III de Madrid, Madrid, Spain Alejandro Rodríguez-González, Centro de Biotecnología y Genómica de Plantas, UPM-INIA, Universidad Politécnica de Madrid, Madrid, Spain Track: Research Presentation Topic: The nature and dynamics of social networks in health Presentation Type: Poster presentation Submission Type: Single Presentation Last modified: 2013-09-25

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Background
Vaccines are among the most successful and cost-effective prevention activities in healthcare and in the last few years we have witnessed a remarkable reduction in the number of people suffering from preventable infectious diseases around the world, above all in European Region. At the same time, with the use of the Internet and with the appearance of Social Media platforms, where it is very common for users to share health information, the anti-vaccination activism has found a useful and easy way to spread their messages and philosophy. In this work we describe the features and content of open groups about vaccines on Facebook, the most widely-used social media platform with millions of users around the globe.
Objective
To determine the features and content of the open groups on Facebook related to vaccines in humans in English and Spanish.
Methods
We carried out a cross-sectional study on the Internet. Using the Graph API (application programming interface) search engine on Facebook, the open groups about vaccines were searched on the 8th of February. Related keywords about the topic and their variations were used (vaccines, vaccinate, vaccination, anti-vac*, immunization) in English and Spanish. The variables studied were: language of the groups, name and description group, number and gender of users, number of posts, date of creation, the most recent update, user country and category (pro and anti-vaccination groups) based on the name, description and content of the 10 last posts on the wall of each group. A web interface was designed in order to facilitate the process of searching the groups and to manage the keywords and the data files obtained containing the related information. SPSS was used for statistical analysis.
Results
318 groups on Facebook were obtained (156 in English (E) and 162 in Spanish (S)) through the Graph API. Among them, in a first step 186 were included in the study to be open groups (98 in English and 88 in Spanish). Of these, 48E and 37S were excluded because the content was unrelated to vaccines in humans or were in other languages (French, Italian, etc.). Finally 101 open groups (50E and 51S) were included with 24,815 members (14,911: 9,984 (67%) women and 4,927 men (33%) in English groups and 9,904: 6,586 women (66.5%) and 3,318 (33.5%) men in Spanish groups). There were a 68% of anti-vaccination groups in English and 55% in Spanish (p=0.176).
Conclusions
Facebook is used as a means of communication and for sharing health information. There are open groups with information about vaccines on Facebook, the majority of them were anti-vaccination groups, as much in English as Spanish. The Graph API is a very useful tool to collect large data sets on Facebook. More analysis and qualitative studies are needed in order to analyze the type of messages used by anti-vaccination activism to spread its ideas in social media. Health organizations and services should consider participating actively in social media in health promotion and educational activities.