Facebook has removed some of the pages — such as the group Unmasking America!, which had nearly 10,000 members — but others remain.
Early in the pandemic, medical authorities themselves were the source of much confusion regarding masks.
In February, officials like the US Surgeon General urged Americans not to stockpile masks because they were needed by medical personnel and might not be effective in everyday situations.
Public health officials changed their tune when it became apparent that the virus could spread among people showing no symptoms.
Yet Trump remained reluctant to use a mask, mocked his rival Joe Biden for wearing one and suggested people might be covering their faces just to hurt him politically.
He did an abrupt about-face this month, claiming that he had always supported masks — then later retweeted Immanuel's video against masks.
The mixed signals hurt, Fauci acknowledged in an interview with NPR this month.
“The message early on became confusing,” he said.
Many of the claims around masks allege harmful effects, such as blocked oxygen flow or even a greater chance of infection. The claims have been widely debunked by doctors.
Dr. Maitiu O Tuathail of Ireland grew so concerned about mask misinformation he posted an online video of himself comfortably wearing a mask while measuring his oxygen levels.