Facebook will no longer allow advertisements that include misinformation about vaccines as part of an effort to reduce the spread of “vaccine hoaxes” on the platform, the company announced on Thursday.

Facebook will also diminish the reach of groups and pages that spread anti-vaccine misinformation by reducing their ranking in search results and on the News Feed, removing them from autofill suggestions in the search bar, and removing them from recommendation features such as “Groups You Should Join”.

The company’s announcement follows increased scrutiny of the role that social media platforms play in amplifying and financing the anti-vaccine movement.

Anti-vaccine propaganda has been going viral on the internet, just as measles is surging in the real world. The US is combatting measles outbreaks in under-vaccinated communities in the Pacific north-west, New York and Texas, while measles cases in Europe doubled from 2017 to 2018 and major outbreaks have hit the Phillippines and Japan. The World Health Organization named vaccine hesitancy – “the reluctance or refusal to vaccinate despite the availability of vaccines” – as one of the top threats to global health in 2019.

On 1 February, the Guardian reported that all of the top 12 Facebook groups and eight of the top 12 Facebook pages surfaced by a search for “vaccination” advocated against vaccines. That report prompted the Democratic congressman Adam Schiff, the chair of the US House intelligence committee, to write a letter to Mark Zuckerberg urging the company to take action against vaccine misinformation.

Networks of closed Facebook groups with tens of thousands of members or more have become loci for anti-vaccine activism and propaganda, including targeted harassment campaigns against pro-vaccine practitioners. Anti-vaccine propagandists have also been using Facebook’s advertising tools to target mothers with fearmongering misinformation about vaccines. And the platform included targeting categories that enabled advertisers to promote content to nearly 900,000 people that Facebook had deemed to be interested in “vaccine controversies”, the Guardian revealed, as well as other categories related to the anti-vaxx movement.

Those advertising categories will now be removed, Facebook said, and advertisers who repeatedly violate the ban on vaccine misinformation may have their ad accounts disabled.

In enforcing the new policy, Facebook plans to rely on organizations such as the World Health Organization and the US Centers for Disease Control and Prevention to define “verifiable vaccine hoaxes”. Among the most tenacious of these false beliefs is the discredited idea that the vaccine for measles, mumps and rubella causes autism. It does not.

“If these vaccine hoaxes appear on Facebook, we will take action against them,” Facebook’s head of global policy, Monika Bickert, wrote in a blogpost. “For example, if a group or Page admin posts this vaccine misinformation, we will exclude the entire group or Page from recommendations, reduce these groups and Pages’ distribution in News Feed and Search, and reject ads with this misinformation.”

The policy change will also extend to Instagram, where misinformation about vaccines will be excluded from recommendations on the “Instagram Explore” or on hashtag pages.

The company is also considering ways to include accurate information about vaccines within the site, such as “at the top of results for related searches, on Pages discussing the topic, and on invitations to join groups about the topic”.

Facebook’s efforts against anti-vaccine misinformation have lagged behind other social media platforms. Pinterest, the visual social network particularly popular among women, explicitly banned the “promotion of false cures for terminal or chronic illnesses and anti-vaccination advice” in 2017, as part of a larger policy against misinformation that “has immediate and detrimental effects on a pinner’s health or on public safety”.

As part of that policy, the platform banned a number of large anti-vaxx boards and disallowed “pins” from the URLs of websites that specialize in health misinformation, such as StopMandatoryVaccination.com. They also “broke” the search tool for certain phrases such as “vaccine” because the results were known to be “polluted”.

YouTube announced in late January that it was reworking its recommendation algorithm to reduce the number of videos that “could misinform users in harmful ways” – a policy that includes some anti-vaccine misinformation. The company also demonetized a number of anti-vaxxer YouTube channels following a report by BuzzFeed News, removing the financial incentive for propagandists.

Following a letter from Schiff on 1 March, Amazon removed several anti-vaccine propaganda movies from its streaming video service.

In a statement Thursday, Schiff said he was “pleased” that Google, Facebook and Amazon “are taking this issue seriously and acknowledged their responsibility to provide quality health information to their users”. Google is YouTube’s parent company.

“The crucial test will be whether the steps outlined by Google and Facebook do in fact reduce the spread of anti-vaccine content on their platforms, thereby making it less likely to reach users who are simply seeking quality, fact-based health information for their children and families,” he added.