Historian and author John Barry is dead certain: If there was a vaccine during the deadly 1918 flu pandemic, the line of Americans waiting for a shot would have stretched from coast to coast.

“It was considerably worse than we’ve seen now — there were special trains to carry away the dead,” recounts Barry, writer of “The Great Influenza: The Epic Story of the Deadliest Plague in History,” in contrasting the century-old plague with its 675,000 deaths against the ongoing COVID-19 crisis.

“They’d all have taken it,” he says flatly.

Nothing is so simple in pandemic-dominated 2020, where the promise of widespread life-saving COVID-19 vaccinations — the first approved Friday night, with the roll out expected this week — was greeted in some corners of a divided nation by skepticism, paranoia and distrust.

“The challenge is going to be to convince people to get vaccinated,” acknowledged Dr. Anthony Fauci in a Facebook live interview last month — a bizarre situation in a nation where the federal Centers for Disease Control projects the current coronavirus death toll of 296,000 could climb as high as 362,000 by Jan. 2.

An Associated Press-NORC Center for Public Affairs Research poll illustrated the stark vaccine schism among Americans, even as the pandemic’s second wave wreaks continued havoc across the country.

According to the poll, roughly one in four Americans say they will not get vaccinated. And another one in four say they remain unsure if they will or won’t get inoculated when the vaccine is made available via the largest vaccination program in U.S. history.

Those are ominous numbers: Unless 70% of U.S. residents get the vaccine, the nation will not reach the level to create herd immunity for those who refuse the shots, experts say.

In a disturbing side note, a recent Gallup poll found a political divide: Only 50% of Republicans were willing to get the COVID-19 vaccine, compared with 75% of Democrats.

Experts are particularly shaken by the plethora of anti-vaccination messages spreading via social media, particularly those describing the pandemic as a hoax. Just last month, a five-minute video appeared online declaring “the COVID hoax was in the works years before the election of Donald Trump, but they started fast tracking it.”

Among the more vocal vaccine critics was Robert F. Kennedy Jr. of Children’s Health Defense, who questioned the Pfizer trials that led to the U.S. embrace of its vaccine.

“The damning safety studies in Pfizer’s late release clinical trial data dump, and the severe (life-threatening) allergic reactions that bedeviled the vaccine’s UK rollout, have raised red flags and public anxiety about the safety of the companies’ mRNA vaccines,” he wrote last week.

Controversial Dr. Jane Orient, executive director of the Association of American Physicians and Surgeons, dismissed the vaccine and suggested Hydroxychloroquine as a treatment in testimony before Congress earlier this month.

“Quarantines, masks, and lockdowns ... have not stopped the pandemic and are unsustainable,” insisted Orient. “Vaccines are touted as a great hope, but have not been shown to prevent contagion.”

Dr. Ali Mokdad, who spent 20 years at the federal Centers for Disease Control, cringes over such unfounded comments.

“We cannot afford this in America,” said Mokdad, a professor at the Institute for Health Metrics and Evaluation. “It’s very dangerous. It’s irresponsible, and quite honestly it’s criminal. These rumors are spread by individuals, by religious groups, by foreign governments — by politicians, too.

“It is beyond imagination that some groups in the United States are attacking vaccines.”

Barry recalled that most Americans during the Spanish Flu epidemic had no problem wearing masks, although they were subject to the same kind of misinformation now spread easily through cyberspace.

“The real problem was fake news, and the government was putting it out,” he said. “And the papers were printing it, that this is an ordinary influenza by another name.”

It was not. The shocking images of the 1918 pandemic endure in the new millennium: Bodies on the streets of Washington. Steam shovels digging mass graves in Philadelphia. Workers in the coal camps of West Virginia using their shovels to bury the dead.