Negative vaccine views spread like viruses on Twitter

Parallels between the spread of viruses and ideas have become well established since Richard Dawkins coined the term "meme" back in 1976. And the rise of the Internet--and social networks in particular--has provided a way of tracking the spread of ideas, the way an epidemiologist follows a virus.

Now researchers have used this analytical approach to track the viral spread of opinions about vaccines. The research paper, published this week in EPJ Data Science, looked at sentiments expressed about the vaccine for H1N1 on Twitter in 2009. When H1N1 began sweeping across the globe, the threat of a deadly pandemic became very real, but from the start some people were as wary of the vaccine as they were of the virus. A fast response was paramount, so vaccines from Novartis ($NVS), GlaxoSmithKline ($GSK) and others were fast-tracked, but shorter testing periods made some nervous.

The researchers found more than 300,000 tweets about the vaccines and categorized them as positive, negative or neutral. Most of the posts were neutral, with positive and negative trailing at 35,884 and 26,667, respectively. The impact of the posts varied by sentiment too. Negative opinions were more contagious than positive ones. So, when someone tweeted a negative view, more of their followers were likely to retweet or send an antivaccine post of their own. In this way, negative views are more likely to spread. A possible action for pro-vaccine education efforts is to increase their activity on Twitter, mitigating the greater contagion of negative views. Yet the study suggests this is counterproductive. Increased intensity of positive posts was linked to a rise in negative tweets--and a fall in those promoting the vaccine--among followers.

One possible explanation is that pro-vaccine posts are seen as being pushy. An alternative approach is to focus on preventing and controlling the spread of negative views, especially when based on rumors or misunderstandings. With Twitter and Facebook now playing a big role in how people share ideas and opinions, it is important for public health campaigners to use social media well. "Ten years ago we talked about Dr. Google; now we can start to talk about Dr. Facebook and Dr. Twitter," study author Marcel Salathe told the PLoS blog.

- here's the paper (pdf)
- see the PLoS blog