Donald Trump had to know it was coming, even if -- to use a Bible Belt expression -- he was preaching to his choir.

"You know what? I believe totally in your freedoms," he said, at a rally in Cullman, Ala. "You got to do what you have to do, but I recommend: Take the vaccines. I did it -- it's good."

Videos of this August 21 event make it clear that quite a few people booed this request by the former president.

Truth is, the longer a health crisis lasts, the more pollsters will find that anti-vaccine citizens have "turned into true believers" who are rock-solid in their convictions, said political scientist Ryan Burge of Eastern Illinois University. He is co-founder of the Religion in Public website and a contributor to the GetReligion.org weblog I have led since 2004.

"At this point, the holdouts are the only people that (pollsters) have to talk to. … They've heard everything, and nothing is moving the needle for them," he said. "In fact, it seems like whatever you say to try to change their minds only makes it worse. These hardcore folks are digging in their heels all the more."

When exploring the most recent Data for Progress poll numbers, it's hard to nail down a religion factor in this drama. As summer began, 70% of non-evangelical Protestants had received at least one shot of COVID-19 vaccine -- but so had 62% of both evangelical Protestants and Catholics. As the author of a book entitled "The Nones: Where They Came From, Who They Are, and Where They Are Going," Burge found it significant that only 47% of the religiously unaffiliated reported receiving at least one shot.

"Religion may be a factor, for some people, but it's not the main thing" causing Americans to be reluctant, he said. "Age is clearly the No. 1 factor, even when you factor in politics. Young Republicans and independents are the same. …

"So how do you reach these people? I mean, independents trust authority even less than Republicans do these days."

Meanwhile, health-care activists interested in changing minds in pews haven't been helped by waves of press reports claiming "white evangelicals" are the largest flock of anti-vaccine believers, according to evangelical writer Daniel Darling, author of "A Way with Words: Using Our Online Conversations for Good" and numerous other popular books.

“Yes, it's true that evangelicals are divided over COVID, but so is everyone else. … There's no one clear reason why so many people are refusing to get vaccinated," he said.

"Our whole nation is divided. It's young vs. old, working class people vs. elites, along with that whole rural vs. urban-suburban political thing. … Trust levels seem to be at an all-time low and that makes it hard to talk about issues that really matter."

At some point, secular and religious leaders who sincerely want to change minds on the vaccine issue will need to "stop calling people ugly names" and try listening to some of their fears and concerns, he said. With that in mind, Darling recently wrote an essay entitled "Why, as a Christian and an American, I got the COVID vaccine" for USA Today.

"Journalists have, at times, selectively shamed certain populations for failure to wear masks and for gathering while ignoring others," he wrote. "We've all watched elitism, a lack of transparency and a general failure to listen to the concerns of people who live at the end of their decisions create major distrust in the foundational institutions of our society. …

“I'm not writing this to shame anyone. I think it is perfectly reasonable to have questions and skepticism about a new vaccine. Injecting a new chemical in your body is a very personal decision. Nobody should shame you into it."

The drumbeat use of the word "shame" was intentional, he said, reached by telephone. It's especially important for religious leaders to avoid trying to shame their people, even as they attempt to reason with them.

"Before you're going to be prophetic, you need to be pastoral," said Darling. "You have to show people that you want to be a good shepherd. That takes empathy. That takes skill. But that's what we need when people are so divided. We need to build trust."