WASHINGTON (AP) — Last spring, as false claims about vaccine safety threatened to undermine the world’s response to COVID-19, researchers at Facebook found they could reduce vaccine misinformation by tweaking how vaccine posts show up on users’ newsfeeds. Yet despite evidence that it worked, Facebook took a full month to implement the changes at a pivotal time in the global vaccine rollout. Facebook’s own documents also reveal how comments on posts are a hotbed for anti-vaccine messages. But when another researcher suggested disabling comments on vaccine posts, that idea was ignored. Those revelations were contained in disclosures by a former Facebook employee-turned-whistleblower. Facebook says it has made “considerable progress” with downgrading vaccine misinformation in users’ feeds.