What blocks pro-vaccine beliefs?

Despite rhetoric that pits "anti-vaxxers" versus "pro-vaxxers," most new parents probably qualify as vaccine-neutral—that is, they passively accept rather than actively demand vaccination. Unless there is an active threat of polio or whooping cough, they have to remind themselves that injecting their crying infant with disease antigens is a good thing.

Even in these cases, some unease is natural, argue two psychologists in an Opinion published October 29 in Trends in Cognitive Sciences. The act itself is counter-intuitive, and it requires trust in medicine and government that not all of us possess. With campaigns to enhance vaccination compliance showing limited, if any, success, the authors consider what compels someone to vaccinate and the cognitive obstacles that cause pro-vaccine messaging to be rejected.

"Even if people have strong anti-vaccination beliefs, it's not because they are gullible; they have reasons that you can understand when you try to see things from their perspective," says co-author Hugo Mercier of the University of Neuchâtel in Switzerland.

Mercier and co-author Helena Miton of the University of Lyon in France compare vaccination to bloodletting—all the rage until the late 19th century to treat a variety of ailments. If someone had a headache, let blood, and felt better, it was easy to explain cause and effect, even if it was not scientifically sound. This intuitive association drove bloodletting's popularity. Bloodletting is intuitive in spite of its lack of efficacy. Vaccination is counter-intuitive in spite of its efficacy.

In times of health, it becomes harder to experience and share the benefits of vaccination, and so negative views—such as the "vaccines cause autism" argument—are more likely to spread, say the authors. The counter-arguments for these claims also raise questions about which sources can be trusted, whether unvaccinated people are significantly more likely to get sick, and the side effects of vaccination. This makes messages that target vaccine hesitancy, especially if they come from government agencies or pharmaceutical companies, less likely to have an effect.

The community can also shape views on vaccinations. "If you believe in something, and science or your community doesn't share these beliefs, usually it is not a comfortable state to be in," says Mercier. "Fortunately, in most cases, communities adopt views that are in consensus in science, but there are exceptions, and if there are strong social pressures, it can be hard to change one person's mind."

In the long term, forceful measures to vaccinate children do little to increase trust between government institutions and people who hold anti-vaccination views, the authors write. They believe that agencies and pharmaceutical laboratories can make themselves more trustworthy by increasing transparency of clinical trials and engaging in more efficient science communication.