NBC News was blistered on social media Monday for its past claim that a "medical miracle" would have to occur to fulfill President Trump's hopes of a functional coronavirus vaccine by the end of 2020.

A widely shared May 15 NBC News "fact check" said Trump's prediction of having a vaccine by the end of the year was likely a pipe dream. It quoted Emory professor Dr. Walter Orenstein saying "a lot of things could go wrong." Another said a vaccine in a minimum of 12 months was only doable under the "best of circumstances."

"Experts say that the development, testing and production of a vaccine for the public is still at least 12 to 18 months off, and that anything less would be a medical miracle," reporter Jane C. Timm wrote.

As the world watched two New York health care workers receive doses of the Pfizer coronavirus vaccine Monday, some wondered how a "fact check" of Trump's prediction was possible in the first place. 

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Republican spokesman Steve Guest quipped, "4 Pinocchio's for NBC," a reference to the Washington Post's fact-checking guide.

MSNBC repeatedly touted the article on its airwaves that week, with some pundits mocking Trump's optimism. 

"I would bet my left arm that Donald Trump can't spell vaccine, let alone be able to make a prediction about when we're likely to see one," MSNBC contributor and Lincoln Project co-founder Steve Schmidt told a chuckling Joy Reid on May 15.

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A Miami Herald article on Oct. 23 declared, "Trump says COVID-19 vaccine is coming ‘within weeks.’ Experts say that’s not possible." CNN cast doubt on Trump’s September suggestion that every American could receive a vaccine by April by quoting an anonymous source in a report headlined, “Trump says every American can get a coronavirus vaccine by April, but health experts say that's not likely.”

MSNBC's Ari Melber said it would require "basically a miracle happening" for Trump's claim to come true, while headlines like Business Insider's "A coronavirus vaccine probably won't be ready before the end of 2021, according to a Swiss pharmaceutical giant" flashed on the screen.  

Other media members mocked the notion of a vaccine by year's end as well, including these flagged by NewsBusters managing editor Curtis Houck.

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Other news outlets also expressed pessimism about the likelihood of an effective vaccine being deployed by year's end. PolitiFact quoted one expert on April 23 who said it was not unusual for vaccine development to take 10 to 15 years, although it added the coronavirus vaccine was on an accelerated timeline.

"It could end up being less than 18 months, closer to 12, or in the absolutely best case, maybe less than that," University of Maryland professor Dr. Kathleen Neuzil, director of the Center for Vaccine Development and Global Health, said, adding that would be a "tremendous feat."

"The development for an effective vaccine against the coronavirus by even the end of the year would mark a watershed moment in medicine as vaccines typically take several years, if not decades, to succeed," NPR reported on Sept. 9.

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Trump has repeatedly touted the success of Operation Warp Speed, the public-private partnership spearheaded by his administration to produce a viable vaccine and distribute it to hundreds of millions of Americans.

The Food and Drug Administration gave emergency authorization to Pfizer's vaccine last week and is expected to also grant it to Moderna's. Other vaccines are in late-stage trials and could be authorized in the coming months, the New York Times reported.

Fox News' Brian Flood contributed to this report.