CNN  — 

The worrisome Omicron variant lends fresh urgency to President Joe Biden’s months-long grind to vaccinate Americans against the coronavirus. He needs it.

That 78 million Americans still resist protective shots confounds anyone examining the medical evidence of the vaccines’ effectiveness. But the evidence of history, turbocharged by the modern Republican Party’s extremism, makes vaccine resistance no mystery – and Biden’s effort a slog even after nearly 800,000 deaths from Covid-19.

Just as they’ve elevated voting restrictions over the protection of democratic elections, Republican officials have elevated exploiting the pandemic over ending it. While GOP attorneys general bogged down vaccine mandates in court, GOP senators last week threatened to shutter the federal government to block them even as some Republicans slam Biden for failing to contain the pandemic.

They seek approval from rank-and-file Republicans, who represent the locus of vaccine refusal. Fully 60% of unvaccinated Americans, according to a recent Kaiser Family Foundation survey, identify with the GOP.

That proportion increased from 42% in April even as the pandemic killed Republicans in disproportionate numbers. A CNN analysis of data from Johns Hopkins University shows the risk of death from Covid-19 is 50% higher in states that former President Donald Trump won in 2020 than in states he lost.

A health care worker prepares a dose of the Pfizer-BioNTech Covid-19 vaccine.

Twenty-six percent of Republicans told the Kaiser Family Foundation they definitely won’t get vaccinated, compared with 14% of independents and 2% of Democrats. Foundation polling director Liz Hamel says the Republican number hasn’t budged in statistically significant ways in a year.

It is not a uniquely American phenomenon. Parts of Europe, including those marked by the anti-government, populist nationalism prominent within the GOP, have held down vaccination levels, such as Germany and Austria.

But those countries and others with advanced economies have still fully vaccinated higher shares of their populations than America’s 60%. CNN data, for example, shows Germany at 68%, Austria at 66%, Australia at 73% and Canada at 76%.

America has a century of experience with the problem. What Biden now faces vexed predecessors in struggles against smallpox, polio, measles and swine flu.

“Vaccine resistance is as old as vaccination itself,” observed Elena Conis, a University of California, Berkeley, medical historian.

Resistance typically flows from three overlapping sources: religious objections, assertion of individual rights and disputes over medical risks. As early as the Asian flu in 1957, the Gallup poll measured higher vaccine resistance among Republicans.

The GOP’s evolution since then has made it even more resistant. Its most influential constituencies – White evangelical Christians, blue-collar workers, rural residents – feel increasingly threatened by 21st-century racial, cultural and economic changes and hostile to well-educated “elites” in government and big cities.

One striking shift: In a Gallup poll this summer, just 45% of Republicans expressed confidence in science, down from 72% in 1975. The corresponding 2021 figures among Democrats and independents were 79% and 65%. And polls find Republicans far more likely to say the dangers of the coronavirus have been exaggerated.

Trump bent to that sentiment and inflamed it last year. He clashed with public health authorities even when following them might have helped him politically by tempering the pandemic.

He led attacks on Dr. Anthony Fauci, the government’s preeminent infectious disease expert. Trump championed vaccine development early on – and got the shots himself after surviving Covid-19 – but has not aggressively promoted vaccinations since.

Biden has followed the familiar vaccination campaign playbook. It begins with making shots easily available, then uses persuasion. In 1956, public health authorities courted reluctant youth by giving Elvis Presley the new polio vaccine on television; Biden enlisted pop star Olivia Rodrigo, among others.

The next step is tangible vaccination incentives, such as the $100 payments Biden asked states to offer those previously reluctant. Government-imposed mandates represent the last resort.

“I waited until July to talk about mandating, because I tried everything else possible,” the President told CNN’s Anderson Cooper in an October CNN town hall.

By then, the Delta variant was fueling a pandemic resurgence after months of falling coronavirus case counts. Some experts, like former Baltimore health commissioner Dr. Leana Wen, a CNN contributor, say that earlier mandates could have blunted Delta.

“If he’d come out with (mandates) earlier, there’s a pretty high likelihood it would have turned people off,” countered Andy Slavitt, a White House Covid adviser during the administration’s opening months. In past vaccination campaigns, mandates have triggered backlashes.

So far, government and private-sector mandates have succeeded in prodding the hesitant without melting hard-core resistance. The shares of Blacks and Hispanics reporting that they’ve received at least one dose, once far behind the share of Whites, has edged toward parity.

Last week, Biden outlined new steps to encourage vaccinations in hopes of preventing a winter surge. He shied away from requiring proof of vaccination for domestic air travel, which White House aides fear would snarl airports, hurt the economy and anger voters.

That defied outside health experts, who say the last resort for using vaccination to squelch the pandemic has been reached.

“There’s no more persuasion left,” said Anna Kirkland, a professor of health policy at the University of Michigan.

But even that, history shows, would take Biden’s vaccination campaign only so far.

“Catch as many as you can,” Conis concluded. “With vaccinations that’s usually the best we can do.”