Instagram is adopting new measures to ban anti-vaccine content from its platform.

The social network had previously blocked all hashtags that directly promote false claims such as #vaccinescauseautism, but it will now also block general hashtags if found to spread misinformation about vaccines, the company said on May 9.  

“If the hashtag was #vaccines1234, if it contained a high proportion of known vaccine misinformation, we would block that hashtag entirely,” said Karina Newton, Instagram’s global head of public policy. Instagram declined to specify the exact proportion of posts with misinformation needed to block a hashtag, citing safety issues.

The company will review posts removed under its new misinformation policies and use machine learning to draw connections between posts and hashtags to help identify future posts with such information. However, Instagram will not take action against people or accounts that it identifies as promoting anti-vaxxer messaging, according to BBC.

The social media network also specified that it is using guidelines from the World Health Organization (WHO) to regulate information. “Known vaccine misinformation” refers to misinformation that has been verified as false by the World Health Organization, the Centers for Disease Control, and similar organizations, the company said. Such misinformation includes claims that vaccines are not safe and can cause autism or other illnesses — these claims are not backed by science.

Social media platforms have been accused of helping to grow the anti-vaxxer movement by circulating misinformation that has existed for decades.

“Vaccine hesitancy is not new — it always has been around,” Eve Dubé, former member of the WHO working group on vaccine hesitancy who currently leads the Social Sciences and Humanities Network of the Canadian Immunization Research Network, recently told Global Citizen.“With social media and internet, rumors or anti-vaccine content can spread much faster than it used to.”

Read More: Almost 1,000 Children Have Died of the Measles in Madagascar Since October

Technology has made it simpler for users to share misleading content without vetting. Algorithms not made public but used by Facebook and YouTube directed users searching for vaccine information towards anti-vaxxer pages or content.

“When we would put things on YouTube, it was followed by an anti-vaccination video,” Amy Pisani, executive director of Vaccinate Your Family, the nation’s largest nonprofit dedicated to advocating for vaccinations, told NBC.  

Vaccinate Your Family previously posted several interviews with medical professionals, public announcements and clips of children who died of diseases preventable by vaccines, on YouTube.

But those messages were soon lost. YouTube’s recommendation system, that pops as a message box on the upper-right corner, led viewers to anti-vaccination videos according to Pisani.

“They were insane. Videos like ‘My child was harmed by the DTaP’ or ‘My child can’t walk anymore,’ every conspiracy that you can imagine would come after ours,” Pisani said.

"They actually started running right after our video was over, so if you blinked for a minute, you wouldn’t know it was a new video.”

The Guardian also reported in February that anti-vaxxer content was ranked highly in search results for pages about vaccines, and YouTube’s recommendations directed searchers to anti-vax misinformation.

Read More: Why You Should Never Skip Your Vaccines Again

Health professional and vaccine researchers were also regularly threatened by anti-vaxxers on social media.

Instagram said it’s aiming to introduce an educational pop-up for users that search for information about vaccines; however, the content of this pop-up has not yet been finalized. The anti-vaxxer message being spread on social media has had real world consequences.

The United States, Canada, and Philippines are suffering unexpected measles outbreaks. Cases have more tripled in Europe between 2017 and 2018. And a recent study by the Centers for Disease Control and Prevention suggests that the anti-vaxxer movement is responsible for the outbreaks. The WHO even listed vaccine hesitancy as one of 2019’s global health threats.

Starting early March, social media giants like YouTube, Facebook, and Instagram announced campaigns to combat the spread of misinformation around vaccines.

YouTube launched a fact-check alert and blocked ads on channels that promote vaccine conspiracy theories. Facebook announced a “remove, reduce, inform” policy that will not only remove all anti-vaccine posts, but will also provide users with accurate information from expert organizations.

Despite the announcement of its effort to combat vaccine misinformation, hashtags such as #VaccinesHarm are still active and attracting traffic on Instagram, CNN Business found.  CNN also reported that if while Instagram will no longer show users blocked hashtags like #vaccinescauseautism, it will still display variants of the tag, like #vaccinescauseautismreadthestudies, when searched.

An Instagram spokesperson responded to the concern by saying that the review process is ongoing and additional measures to limit the spread of misinformation are being considered.

“It’s going to take some time to continue to work on it,” Newton said.