Facebook said on Tuesday it will ban anti-vaccination ads, following widespread pressure on the social network to curb harmful content.

Under the new global policy, the company will no longer accept ads discouraging people from getting vaccines; ads that portray vaccines as unsafe or ineffective; or ads claiming the diseases vaccines prevent are harmless.

"We don't want these ads on our platform," Facebook officials Kang-Xing Jin and Rob Leathern wrote in a blog post. "Our goal is to help messages about the safety and efficacy of vaccines reach a broad group of people, while prohibiting ads with misinformation that could harm public health efforts."

The new policy also applies to Instagram. Facebook said it will start enforcing it in the next few days.

The move is a reversal of Facebook's longstanding reluctance to police what people are allowed to say, saying it wants to encourage free speech. Public health groups and other critics have urged it to stamp out widespread misinformation on its platforms, which have more than 3 billion monthly active users.

This year the company has cracked down on hoaxes and falsehoods about the coronavirus. It had already banned vaccine misinformation and hoaxes identified by global health organizations like the World Health Organization and the Centers for Disease Control and Prevention.

The new policy is not a total ban on opposition to vaccines. The company will still accept ads that advocate against government vaccination policies. But those ads cannot explicitly discourage vaccination or make false claims, Facebook spokesperson Devon Kearns told NPR.