Anti-vaxxers use pseudoscience and misinformation to support their claims, presenting false information as "scientific evidence" to push the idea that vaccinations are linked with autism, brain injury and other dangers. Researchers analysed the content of almost 500 anti-vaccination websites to better understand why their messages are so persuasive.

The team from Johns Hopkins University Bloomberg School of Public Health are set to present their research at the American Public Health Association's annual meeting. The research comes following an upsurge in the anti-vaccination movement over recent years.

Campaigners cite a host of reasons why you should not vaccinate a child. This includes claims that vaccines contain toxic chemicals, that they overwhelm a child's immune system, that they cause autism, that they are never 100% effective, and even that they contain aborted foetus cells. They also say pharmaceutical companies and the government cannot be trusted, and that there are many 'scientists' who support their views.

A 2008 study in Nature Immunology looked at the anti-vaccination movement. Titled A Case of Junk Science, Conflict and Hype, the paper noted that the "decrease in uptake of the MMR vaccine fuelled by vaccine sceptics is the main cause behind the resurgence of these diseases in recent years".

Yet their message persists. In their latest report, scientists led by Meghan Moran analysed the content of 500 anti-vaccination websites. They searched the web using terms such as "vaccine danger" and "immunisation dangers" to find a mix of websites, blogs, Facebook pages and health websites dedicated to the movement.

They then coded the content for the misinformation presented, the source of the misinformation, the types of persuasive tactics used and the behaviour and values promoted by these websites. They found more than two thirds used what they called "scientific evidence" to support the idea that vaccinations are dangerous, with a third having stories to reinforce their views. Around two thirds said they cause autism and almost half said they cause "brain injury".

However, amid the misinformation, they also found many sites promoting positive behaviour, such as healthy eating, breastfeeding and organic food. Moran said: "The biggest global takeaway is that we need to communicate to the vaccine-hesitant parent in a way that resonates with them and is sensitive to their concerns.

"In our review, we saw communication for things we consider healthy, such as breastfeeding, eating organic – the types of behaviour public health officials want to encourage. I think we can leverage these good things and reframe our communication in a way that makes sense to those parents resisting vaccines for their children."