Since the World Health Organization declared the novel coronavirus an international health emergency in January, Facebook Inc. has removed more than 7 million pieces of content with false claims about the virus that could pose an immediate health risk to people who believe them.

The social media giant, which has long been under fire from lawmakers over how it handles misinformation on its platforms, said it had in recent months banned such claims as "social distancing does not work" because they pose a risk of "imminent" harm. Under these rules, Facebook took down a video post on Wednesday by U.S. President Donald Trump in which he claimed that children are "almost immune" to COVID-19.

But in most instances, Facebook does not remove misinformation about the new COVID-19 vaccines that are still under development, according to the company's vaccine policy lead Jason Hirsch, on the grounds that such claims do not meet its imminent harm threshold. Hirsch said the company is "grappling" with the dilemma of how to police claims about new vaccines that are as yet unproven.