The anti-vaccine movement is growing due to the easy access of information from social media sites such as Facebook, leading to calls for these sites to remove anti-vaxx disinformation.

Facebook has announced that it is cracking down on anti-vaccine disinformation in its platform, according to a report from Bloomberg. In a statement, the company said that it is “exploring additional measures to best combat the problem.” This might include “reducing or removing this type of content from recommendations, including ‘Groups You Should Join,’ and demoting it in search results, while also ensuring that higher quality and more authoritative information is available.”

US congressman Adam Schiff wrote a letter to Facebook CEO Mark Zuckerberg, urging him to take action against “messages that discourage parents from vaccinating their children.” Schiff added that anti-vaccine disinformation is a direct threat to public health and reverses the progress made in tackling vaccine-preventable diseases.

“There is strong evidence to suggest that at least part of the source of this trend is the degree to which medically inaccurate information about vaccines surface on the websites where many Americans get their information,” Schiff wrote in his letter. “The algorithms which power these services are not designed to distinguish quality information from misinformation or misleading information, and the consequences of that are particularly troubling for public health issues.”

The Guardian recently reported that Facebook was accepting ads from anti-vaccine groups and pages. A quick search on Facebook also showed anti-vaccine groups and pages being on the top of searches for vaccination information. A number of anti-vaxx groups are also active, including “Stop Mandatory Vaccination,” which has more than 120,000 members.

In the Philippines, the anti-vaccination movement has gained momentum, partly due to hysteria bought about by the Dengvaxia controversy. An opinion poll by the London School of Hygiene and Tropical Medicine revealed that just 32% of the 1,500 Filipinos surveyed trust vaccines – down from 93% in 2015.