Facebook puts anti-vaccine groups at the top of many vaccine-related searches on the platform, another failure of the world’s largest social media network to curb the spread of misinformation on its platform.

As Facebook grapples with how to handle hoaxes on its platform, the site still remains a hub for conspiracy theories about how vaccines cause autism or other diseases.

Facebook groups and pages devoted to promoting vaccine skepticism rank at the top of Facebook searches for vaccination-related terms like “vaccines,” helping those groups spread false claims that vaccines cause autism and the like.

The top results for vaccine information on Facebook, for example, returned “anti-vaxx” groups with names like “United Against Vaccines,” Vaccines Injury Stories,” “Vaccines Exposed,” and pages related to opposing mandatory vaccination rules.

The groups and pages push a hard line against vaccinations, often paired with pictures of babies and needles. The groups often include memes claiming that doctors don’t learn enough about vaccines in medical school to be trusted.

One Facebook page, “The Truth About Vaccines,” has more than 130,000 followers receiving posts with articles claiming, among other things, that children who don’t receive vaccines are healthier than those who do. The operator of another page, “Stop Mandatory Vaccination,” assured the page’s more than 110,000 followers in a post that they don’t need vaccinations.

A Facebook spokesperson told The Daily Beast it removes information that violates its community guidelines and allows users to tailor the information they see on the site. Facebook has also attempted to offer third-party fact-checking alongside inaccurate articles that appear in a user’s News Feed. But Facebook refused to comment on why it allows anti-vaccine hoaxes to spread on the site, or why it makes it so easy to find anti-vaxx groups through searches.

Facebook has been under pressure since the 2016 election to control the spread of hoaxes on the site. Days after the 2016 election, Facebook CEO Mark Zuckerberg vowed to hinder the spread of “fake news” that was promoted by the Russian government during the election to help Donald Trump against Hillary Clinton.

Nearly two years later, though, Facebook is still struggling. And while fake news promoted by Russian operatives could have swayed some voters, anti-vaccination groups on the site have a far more serious impact by reducing vaccination rates.

Vaccine fears like those spread on the Facebook groups have helped create pockets of children who haven’t received vaccines. Anti-vaccine skeptics have driven up the number of families refusing to vaccinate their children, according to one 2018 study, creating “hot spots” of unvaccinated people in cities like Portland, Detroit, and Houston.

A measles outbreak at Disneyland in 2014 spread across the country via unvaccinated children, ultimately infecting 145 people in the United States along with others in Mexico and Canada. In 2017, Minnesota faced a measles outbreak after anti-vaccination groups convinced some parents not to vaccinate their children.

“ while fake news promoted by Russian operatives could have swayed some voters, anti-vaccination groups on the site have a far more serious impact. ”

In a research paper published last year, two Australian researchers studied how anti-vaccination Facebook users, most of whom are female, cluster in tight networks of Facebook groups on the site. Because anti-vaccination groups are spread across many smaller Facebook groups, rather than clustered around one or two main hubs, Smith said that makes it difficult for Facebook to take much action against the groups.

“They’d just go somewhere else, and set up shop again,” Naomi Smith, a lecturer at Federal University Australia who co-authored the paper, said.

Social networks like Facebook are key to the spread of anti-vaccination fears, according to Smith, because they link people who would otherwise have found little traction for their fears about vaccinations in the real world.

Within those groups, repeated references to the same discredited anti-vaccination information can have an echoing effect that makes the information seem more credible, according to Smith.

“You’ve got this in-built community reinforcing those kind of very primal fears around parenting, that you don’t want anything to happen to your child,” Smith said.

The anti-vaccine groups can also come off as deceptively moderate, according to Smith, an issue that’s complicated by Facebook allowing the groups to feature in the top searches for vaccine-related information. Rather than loudly proclaiming opposition to vaccines, the Facebook groups can position themselves around parental choice or “natural” health.

Smith said Facebook’s efforts to control fake news haven’t had an effect on anti-vaccine groups.

“They seem to be doing just fine,” Smith told The Daily Beast.