On Facebook, misinformation about the coronavirus that has killed more than 100 people in China continues to spread worldwide despite efforts and pledges by the social media company to eliminate fake news.

One post on Facebook said the U.S. patented a vaccine years ago for the coronavirus. It is a hoax.

The false information was posted January 21, and was still up a week later on a public page, despite being linked to in a story by the Factcheck.org about it and other posts spreading inaccurate information on Facebook. The post has been shared 4,800 times, and has 432 comments. One comment to the false Facebook post includes a link to a website that calls the coronavirus itself a hoax and suggests that drinking Corona beer alone will cure the virus.

Screen shot of post about coronavirus on Facebook. Courtesy of Facebook

Another comment to the Facebook post links to a website that said the Bill and Melinda Gates Foundation is connected to the recent disease outbreak. It predicts world health authorities will soon cut off access to the Internet, or force social media sites to suppress what it said is the truth about the virus.

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To be clear, none of that is correct, either.

And yet, the Facebook posts live on, as do others. In the wake of the 2016 presidential election, in which U.S. intelligence officials believe Russia used Facebook and other social media outlets to spread false news and help sway the outcome to Donald Trump, the social media giant has pledged to fight misinformation on its website.

Facebook formed an alliance with media outlets and other fact checkers, including FactCheck.org, to help it determine what news was false and either remove the posts or label them as false.

After much criticism, for instance, Facebook banned InfoWars' Alex Jones, who has spread numerous conspiracies, including that the Sandy Hook school shooting was staged. Last month, Jones was ordered to pay $100,000 to one victim's family for Jones' statements about the shooting.

Facebook ran an ad campaign with posters that read "Fake news is not your friend." More recently, Facebook weathered criticism on its decision to allow political advertising with no fact checking. Twitter by contrast has said it won't allow political advertising on its service.

But the coronavirus episode shows that Facebook's ability to tamp down on fake news, and its willingness to do so, is still limited at best.

Facebook, through a spokesperson, described to CBS MoneyWatch its third-party fact-checking partnerships as "dramatically reducing" the company's distribution of false news. The company said customers get a pop-up warning when they share posts that contain information that fact checkers have deemed inaccurate.

"This situation is fast-evolving and we will continue our outreach to global and regional health organizations to provide support and assistance," a Facebook spokesperson said in a statement.

Facebook inserts a pop-up that grays out the picture and is labeled "False Information - Checked by independent fact-checkers" on a number of coronavirus posts. One pop-up example includes a false post that said the U.S. government has had a coronavirus vaccine for years, but is not manufacturing it to create and encourage fear. Facebook, though, hasn't removed the post, and the text and link to what the users' claims to be the patent are still there. Comments are also still allowed.

Screen shot of a blocked post on Facebook about the coronavirus. Courtesy of Facebook

Coronavirus is actually a class of viruses that were identified years ago, many of which do have patented treatments. The strain of coronavirus that is believed to have originated in Wuhan, China, and is currently spreading and worrying health officials is new and has no known cure.

Other Facebook posts, including the one from last week claiming a vaccine for the coronavirus exists, have been paired by Facebook with a trio of stories, including the one from FactCheck.org, in a box titled Related Articles that call the patent claim false. The Facebook spokesperson said the Related Articles box is part of the post and gets shared with the post. But the Related Articles box is not immediately visible in a user's newsfeed — it only appears when the date of the post is clicked.

Rival social media site Twitter is also having trouble containing the plague of coronavirus-falsehood contamination.

For instance, Facebook has put a pop-up blocking a post with a screen shot of a tweet by prominent conspiracy theorist Jordan Sather that appears to be one of the first making the false patent claim, and even called coronavirus a "fad." On Twitter, however, where Sather has 115,500 followers, the tweet remains live and unblocked. It has been retweeted 4,700 times and liked nearly 6,000 times.