Facebook has a history of running ads that spread misinformation about vaccinations and people are angry.

Just before Christmas, Facebook halted advertisements on its site that claimed that vaccines may cause autism, The Washington Post reported. It’s not the first time that the social network has done this: Last August, Facebook required advertisers to list their stance on contentious issues.

More recently, back in October, it was accused of not doing enough to remove anti-vaccine ads from its site.

Meanwhile, there is a growing tide of calls for the social network to share its user data with regulators in order to help them combat misinformation about vaccines.

Here is what you need to know.

The uproar is over a page

The controversy began in October when Scott Schaffer, a senior data scientist, noticed a change in Facebook’s advertising policy. In the past, a piece of anti-vaccine content could appear on a page’s page if it was shared with a large enough audience.

In October, however, Facebook limited the audience for any such ads that could potentially pose “false, misleading or deceptive” claims. Now, the same advert had to be shared with a 1,000 or more people, according to a New York Times report.

On September 18, Google implemented a similar change.

This information was suddenly available to the public, and the number of shares counted towards the audience criteria. Facebook soon removed the controversial new policy after complaints from the American Association of Pediatrics.

Finally, Facebook said in a statement that it was simply implementing a number of small changes to its ad platform.

“While we do not currently remove content based on the number of shares, this new policy does allow us to make the cases we do remove in a more transparent way,” a Facebook spokesperson said.

These changes, however, have not stopped the vaccine hate from spreading.

Can the FB finally stop 'public figures' spreading anti-vaccine propaganda? (updated: FB responded) pic.twitter.com/5eyu67mHPg — Holly Gordon () October 24, 2018

Are Facebook adverts really anti-vaccine?

After the anti-vaccine rage reached a crescendo, Facebook issued an official statement on Monday, saying that it has been running anti-vaccine ads from December 6.

However, the company also noted that it is “not allowed to share content that contains a misleading statement about the potential risks of vaccines.”

What it means, and how this is different

Since August, Facebook has required that all ads mentioning controversial topics indicate which side the advertiser endorses and why.

Previously, the situation was much different. Before Facebook updated its policy, any individual’s personal information was required to back up claims made in an ad. For instance, on “issues like immigration, climate change, and net neutrality,” users were required to list their views in order to know whether they had been promoted on the social network.

If an individual shared an ad with 10,000 users, no additional information would be required. It was still a surprise that in many cases the advertising platform pushed views that are drastically opposed to the majority of Americans.

If users read the ad, they would know that the ad was run by a nonprofit opposed to vaccinations. Still, the ad appeared when the users read the text, rather than the name of the ad and the nonprofit’s name.

In the new Facebook advertising policy, users would no longer see a change to the details of a linked page with their “sensitive facts.” This seems like it will fix that situation.

The Americans For Truth campaign

According to AdAge, the anti-vaccine content will be marketed through the Americans For Truth campaign, an organization that has managed to drum up a significant amount of buzz for the anti-vaccine cause.

On its website, Americans For Truth said it “aims to inform and train the public to respond to, and shape, the debate on vaccines.”

Americans For Truth spent hundreds of thousands of dollars in the summer of 2017 to buy ads on Facebook about the connection between vaccines and autism. Though ads on the network discussed autism extensively, Facebook did not come under fire over this time period as it did later.

It was only after the 2015 measles outbreak that Facebook was required to reveal its policies on the matter.