(NBC News) - Unvaccinated Americans believe the vaccines are more dangerous than Covid-19, while vaccinated Americans believe the delta variant is worrisome enough that they continue to mask in public and avoid large gatherings. And even though almost 165 million people in the U.S. are fully vaccinated and the delta variant is raging across the country, the percentage of U.S. adults who say they oppose the Covid vaccines has remained unchanged since December, according to a report from the Kaiser Family Foundation.
The survey's findings, published Wednesday, show some of the striking differences between the two groups and the challenges facing public health officials.
The Kaiser Family Foundation surveyed 1,517 adults in mid-July about their thoughts and experiences surrounding the vaccines. At the time, Covid-19 case numbers were rising because of the delta variant of the coronavirus, but the Centers for Disease Control and Prevention had not yet recommended indoor mask use in areas with high transmission rates.
Still, 62 percent of vaccinated adults said news of the variant had prompted them to continue masking in public places, and 61 percent said they avoided large gatherings because of the variant.
By contrast, 37 percent of unvaccinated adults said the variant had prompted them to wear masks, and 40 percent said they steered clear of crowds.
"When we look at who's more likely to be changing their behaviors because of delta, it's vaccinated people versus the unvaccinated people. That's what really stands out," said Liz Hamel, vice president and director of public opinion and survey research at the Kaiser Family Foundation.
The research group has been conducting surveys since December to track changes in attitudes about the vaccines.
One finding has not changed. Staunch opposition to the vaccines has hovered around the 13 percent-to-15 percent range from the beginning. In the latest report, 14 percent said they would "definitely not" get vaccinated.
Those who remain unvaccinated were more likely than people who have had the shots to say media outlets have exaggerated the seriousness of the pandemic and to mistakenly believe that there is more to fear from the vaccines than from Covid-19.
Demographics of each group are largely divided by political affiliation.
The "differences are to a large degree driven by unvaccinated Republicans," the authors wrote. "Majorities of Republicans say they never wear a mask outdoors, in crowded outdoor places, at work, or in a grocery store. Democrats are more likely to report wearing a mask at least most of the time in all of these locations."
The results may not reflect any potential impact of recent messages from Republican lawmakers encouraging their constituents to get vaccinated.
Sen. Lindsey Graham, R-S.C., expressed appreciation for the vaccines Monday, even though he tested positive for the virus after having been fully vaccinated. "I am very glad I was vaccinated because without vaccination I am certain I would not feel as well as I do now. My symptoms would be far worse," he wrote in a statement.
There appears to be a growing acceptance of the vaccines in places that have logged the greatest increases in case numbers.
"Daily vaccination rates have more than doubled in eight states" with high numbers of Covid-19 cases, Jeff Zients, the White House Covid-19 response coordinator, said at a briefing Monday.
Some of the increase may be attributed to those whose friends and family have become ill with the virus. Hamel of the Kaiser Family Foundation suspected that the next few surveys may reflect that change in attitudes.
"I think there is still a chance that circumstances on the ground could accelerate people's desire to go out and get the vaccine," she said.
Overall, 70 percent of adults in the U.S. — more than 180 million people — have had at least one dose. Meanwhile, nearly 35 million cases of Covid-19 have been reported since the beginning of the pandemic, and more than 611,000 people have died.