Twitter as a source of vaccination information: content drivers and what they are saying.

Twitter is a popular source of health information. This study reports a content analysis of posts about vaccinations, documenting sources, tone, and medical accuracy. Results can help explain patient knowledge and directions for educational campaigns. A set of 6,827 tweets indicates professional sources were shared most and treated positively. Two-thirds of shared medical content were substantiated. One-third of messages were positive, counter to other research and suggesting that users apply critical thinking when evaluating content.