An increasing number of parents these days have concerns about vaccines. And as anyone who's tried to rationally debunk these concerns with science will be aware, it's frustratingly hard to change people's minds, despite the overwhelming amount of evidence backing up the safety of immunisation. In fact, research has shown that the more you argue with anti-vaccers, the more set they become in their opinions.

But researchers in the US have analysed several different methods of reassuring parents who are skeptical about vaccines, and the results show that sometimes it's better to stop arguing, and simply let pictures do the talking. 

The study found that focussing more on the dangers of the diseases that vaccines prevent is much more effective than trying to use science to debunk common myths. Specifically, photos of children suffering from vaccine-preventable diseases such as measles and smallpox seemed to be the most effective way to make anti-vaccers re-evaluate their position.

"It's sort of appealing to directly confront people about their beliefs, but that sets up a context for an argument, and then they respond by arguing back," one of the researchers, Derek Powell from the University of California, Los Angeles, told Joshua A. Krisch from Vocativ. "If you tell people that these are contagious diseases and that there are serious benefits to getting vaccines, you can get improvements in people with negative attitudes toward vaccines."

In the study, the researchers quizzed 315 participants on their attitudes about vaccines. Around two-thirds held some degree of skepticism regarding vaccines, while only one-third were positive about them.

The researchers then split these pro- and anti-vaccers evenly into three groups, and asked each to consider different reading materials in an attempt to convince them that vaccines are safe and worthwhile.

The first group looked at material from the Centres for Disease Control and Prevention, which explained in detail the scientific evidence showing no link between vaccines and autism, and also highlighted research that shows how important vaccines are to public health.

That all sounds pretty compelling, but the skeptics in the group weren't convinced.

The control group was simply asked to read an unrelated statement about bird feeding and, unsurprisingly, this also didn't change their minds about vaccines - but what's depressing is that the bird feeding statement and the scientific evidence had about the same impact when it came to changing people's minds… which is, no impact at all.

The third group, on the other hand, didn't talk about the safety of vaccines. Instead they read materials on the dangers of vaccine-preventable diseases, such as measles, mumps and rubella - and this material included graphic images of exactly what those diseases look like in children.

They also read the personal account of a woman whose 10-month-old son almost died from measles, and it was only this last group showed a substantial increase in support for vaccines, regardless of whether they were parents or not.

"It's more effective to accentuate the positive reasons to vaccinate and take a non-confrontational approach - 'Here are reasons to get vaccinated' - than directly trying to counter the negative arguments against vaccines," lead researcher on the study Keith Holyoak said in a press release. "There was a reason we all got vaccinated: Measles makes you very sick. That gets forgotten in the polarising debate on whether the vaccine has side effects."

With almost 9 million children in the US alone now at risk of contracting measles as a result of under-vaccination, this research is more important than ever, and provides science-lovers some guidelines for talking to people about vaccinations. 

"Try not to be directly confrontational," said Holyoak. "Try to find common ground, where possible, and build on that."

And if that fails? Try your luck with a handy picture, like this one, or this one (warning: they're not for the faint-hearted). Good luck.

The research was published in PNAS.