Researchers examine why ‘anti-vaxxers’ decide against immunising

Recent measles outbreaks in Ireland, the UK, Italy and the US have made headlines around the world.

Just this month, an outbreak of the disease in the US state of Minnesota surpassed nationwide American totals for all of 2016; a sobering reminder of how highly concentrated populations of so-called 'anti-vaxxers', can elevate an entire community's risk of infection. Around the edges of every headline-grabbing outbreak, there's a vast range of opinions being circulated about the risks and benefits of early childhood immunisation. The vaccination debate maintains a constant presence on social media platforms, where people on both sides frequently share articles and blog posts to support their stance on the issue. These varied viewpoints caught the attention of scientists at the Biocomplexity Institute of Virginia Tech who are conducting a three-year study on the ways online interactions influence beliefs. Their research, published in the journal Vaccine, attempts to break down the ideas that are most closely associated with a pro- or anti-immunisation stance. The group's findings suggest that the debate around vaccination may hinge more on different understandings of risk, responsibility, and credibility than any particular set of scientific data. Gloria Kang, a member of the research team, explains:

"When we mapped out how these arguments are structured, we found that anti-vaccination content tended to focus on children and their need to be protected. Pro-vaccination content, on the other hand, centred on parents and their obligation to keep kids' immunisations up to date, so the basic notion of whose interests are at stake in this debate are completely flipped."

The investigators developed their rankings of vaccination-related concepts shared on social media using "semantic networks." This is a framework frequently used by psychologists to explain how information gets stored in our long-term memory by plugging it into an existing network of related concepts. Psychological research suggests that those related concepts form a pathway the human brain will follow when attempting to recall thoughts and opinions on a topic in the future. Samarth Swarup, a research assistant professor in the Biocomplexity Institute explains that this 'spreading activation theory' means our memories are never accessed directly. Instead, our brains are constantly employing 'landmarks' to find their way back:

"A single phrase can conjure up completely different images in our minds, depending on how that concept is organised in our mental models. For example, we found that pro-vaccination posts tend to closely associate governmental organisations like the Centres for Disease Control with specific research they've performed on vaccine safety, whereas anti-vaccination content aligns the CDC with private business interests, such as big pharma."

Dang says that, looking forward, information from this study could be a valuable tool for scientists and policymakers trying to address the public's mounting concerns about vaccination safety:

"The longer it takes for us to reach a common understanding on vaccination, the more opportunities there will be for diseases like measles to regain their foothold. Understanding which concepts truly speak to the other side could help us waste less time talking past one another."