A large percentage of anti-vaccination websites are presenting significant amounts of misinformation, pseudoscience and non-scientific anecdotes to support their claim that vaccines are dangerous, a new study shows.

As an example, of the almost 500 websites analyzed for the study, around two-thirds claimed vaccination results in autism, despite multiple scientific studies that found no link between vaccines and the condition, the researchers said.

Two-thirds of the sites also presented information they characterized as scientific evidence but that in fact was not, with around a third of the websites offering personal but non-scientific anecdotes to support their claims, they said.

When some of the sites cited as information sources published by peer-reviewed studies, they misrepresented or misinterpreted the studies' findings, they added.

"So the science itself was strong, but the way it was being interpreted was not very accurate," said study author Meghan Moran of the Department of Health, Behavior and Society at Johns Hopkins University Bloomberg School. "It was being distorted to support an anti-vaccine agenda."

For their website study, the researchers used search engines, including Google, Yahoo, Bing and Ask Jeeves, to look for sites featuring words such as "immunization dangers" and "vaccine dangers," which led them to a mix of health and personal websites, Facebook pages and blogs.

The researchers analyzed the content of those sites for persuasive strategies and the accuracy of the content presented.

Understanding the strategies used by anti-vaccine websites could help in developing ways to counteract the negative messages they provide and instead promote childhood vaccinations, the researchers say.

Despite overwhelming evidence of vaccines' abilities to prevent disease, an increasing percentage of parents are choosing to delay or forego vaccination, citing a number of reasons.

Many people turn to the Internet as a source of vaccine information, where both anti-vaccine and pro-vaccine websites can be found.

The mainstream health community has expressed concern about the growing number of parents refusing to vaccinate their children despite the abundance of scientific evidence of the benefits of vaccination.

In 2014, when the Centers for Disease Control and Prevention recorded the highest number of measles cases since the disease was declared eliminated in 2000, the majority of those who contracted measles were unvaccinated.

"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," Moran says.

The researchers presented their findings at the annual meeting of the American Public Health Association, held this year in Chicago.

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