The old and the new: vaccine hesitancy in the era of the Web 2.0. Challenges and opportunities.

The phenomenon known as vaccine hesitancy (a term that includes the concepts of indecision, uncertainty, delay and reluctance) is complex, closely linked to social contexts, and has different determinants: historical period, geographical area, political situation, complacency, convenience and confidence in vaccines. The World Health Organization (WHO) recommends that vaccine hesitancy and any proxy of it should be constantly monitored. Given the growing importance and pervasiveness of information and communication technologies (ICTs), the new media could be exploited in order to track lay-people's perceptions of vaccination in real time, thereby enabling health-care workers to actively engage citizens and to plan ad hoc communication strategies. Analysis of so-called "sentiments" expressed through the new media (such as Twitter) and the real-time tracking of web-related activities enabled by Google Trends, combined with the administration of specific online "surveys" on well-defined themes to target groups (such as health-care workers), could constitute a "Fast data monitoring system" that yields a snapshot of perceptions of vaccination in a given place and at a specific time. This type of dashboard could be a strategic tool that enables public services to organize targeted communication actions aimed at containing vaccine hesitancy.