Some Americans who were hesitant to get inoculated are changing their minds.

They acknowledged that they could have showed up months ago. Many were satisfied that they were finally doing the right thing. A few grumbled that they had little choice.

On a single day this past week, more than a half-million people across the United States trickled into high school gymnasiums, pharmacies and buses converted into mobile clinics. Then they pushed up their sleeves and got their coronavirus vaccines.

These are the Americans who are being vaccinated at this moment in the pandemic: the reluctant, the anxious, the procrastinating.

In dozens of interviews Thursday in eight states, at vaccination clinics, drugstores and pop-up mobile sites, Americans who had finally arrived for their shots offered a snapshot of a nation at a crossroads — confronting a new surge of the virus but only slowly embracing the vaccines that could stop it.

The people being vaccinated now are not members of the eager crowds who rushed to early appointments. But they are not in the group firmly opposed to vaccinations, either.

Instead, they occupy a middle ground: For months, they have been unwilling to receive a coronavirus vaccine, until something or someone — a persistent family member, a work requirement, a growing sense that the shot was safe — convinced them otherwise.

How many people ultimately join this group — and how quickly — could determine the course of the coronavirus in the United States.

Some of the newly vaccinated said they made the decision abruptly, even casually, after months of inaction.

One woman in Portland, Ore., was waiting for an incentive before she got her shot, and when she heard that a pop-up clinic at a farmers market was distributing $150 gift cards, she decided it was time. A 60-year-old man in Los Angeles spontaneously stopped in for a vaccine because he noticed that, for once, there was no line at a clinic. A construction worker said his job schedule had made it difficult to get the shot.

Many people said they had arrived for a vaccine after intense pressure from family or friends.

“‘You’re going to die. Get the COVID vaccine,’” Grace Carper, 15, recently told her mother, Nikki White, of Urbandale, Iowa, as they debated when they would get their shots.

White, 38, woke up Thursday and said she would do it.

“If you want to go get your vaccine, get up,” White told her daughter, who was eager for the shot, and the pair went together to a Hy-Vee supermarket.

Others were moved by practical considerations: plans to attend a college that is requiring students to be vaccinated, a desire to spend time socializing with high school classmates or a job where unvaccinated employees were told to wear masks. Their answers suggest that the mandates or greater restrictions on the unvaccinated that are increasingly a matter of debate by employers and government officials could make a significant difference.

Audrey Sliker, 18, of Southington, Conn., said she got a shot because New York’s governor announced it was required of all students attending State University of New York schools. She plans to be a freshman at SUNY Cobleskill this fall. “I just don’t like needles in general,” she said, leaving a white tent that housed a mobile vaccination site in Middlefield, Conn. “So it’s more like, ‘Do I need to get it?’ ”

Many people interviewed described their choices in personal, somewhat complicated terms.

Willie Pullen, 71, snacked on a bag of popcorn as he left a vaccination site in Chicago, one of the few people who showed up there that day. He was not opposed to the vaccines, exactly. Nearly everyone in his life was already vaccinated, he said, and although he is at greater risk because of his age, he said he believed he was healthy and strong enough to be able to think on it for a while.

What pushed him toward a high school on the West Side of Chicago, where free vaccines were being administered, was the illness of the aging mother of a friend. Pullen wanted to visit her. He felt it would be irresponsible to do so unvaccinated.

“I was holding out,” Pullen said. “I had reservations about the safety of the vaccine and the government doing it. I just wanted to wait and see.”

The campaign to broadly vaccinate Americans against the coronavirus began in a roaring, highly energetic push early this year, when millions were inoculated each day and coveted vaccine appointments were celebrated with joyful selfies on social media. The effort peaked April 13, when an average of 3.38 million doses were being administered in the United States. The Biden administration set a goal to have 70 percent of American adults at least partly vaccinated by July 4.

But since mid-April, vaccinations have steadily decreased and in recent weeks plateaued. Weeks after the July 4 bench mark has passed, the effort has now dwindled, distributing about 537,000 doses each day on average — about an 84 percent decrease from the peak.

About 68.7 percent of American adults have received at least one shot. Conservative commentators and politicians have questioned the safety of the three vaccines that the Food and Drug Administration has approved for emergency use, and in some parts of the country, opposition to inoculation is tied to politics. An analysis by the New York Times of vaccine records and voter records in every U.S. county found that both willingness to receive a coronavirus vaccine and actual vaccination rates were lower, on average, in counties where a majority of residents voted to reelect former President Donald Trump.

Despite the lagging vaccination effort, there are signs that alarming headlines about a new surge in coronavirus cases and the highly infectious delta variant could be pushing more Americans to consider vaccination. On Friday, Jen Psaki, the White House press secretary, said there had been “encouraging data” showing that the five states with the highest case rates — Arkansas, Florida, Louisiana, Missouri and Nevada — were also seeing higher vaccination numbers.