A new poll suggests the United States could be on track to vaccinate at least 70% of the adult population against COVID-19 by this summer.

In the latest survey by the Kaiser Family Foundation, 62% of respondents said they had received at least one dose of a vaccine, up from 56% in April. At the same time, about a third of those categorized as "wait and see" reported that they had already made vaccine appointments or planned to do so imminently.

Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases and a vaccine expert, found the results encouraging.

"I think there are many people who were on the fence who were worried about things moving too rapidly and about possible side effects, but those concerns are being allayed as they see more of their friends and acquaintances celebrating getting vaccinated," said Schaffner, who was not involved in the monthly survey, the COVID-19 Vaccine Monitor.

"They're getting that growing sense of comfort and reassurance that 'people like me' are getting vaccinated," which, he said, was essential to instilling confidence in the vaccines.

The two demographic groups reporting the greatest increase in vaccination rates from April to May were Latino adults (from 47% to 57%) and adults without college degrees (from 48% to 55%).

The telephone survey of 1,526 adults was conducted in English and Spanish from May 18-25.

On May 10, the Food and Drug Administration authorized the vaccine made by Pfizer and BioNTech for children ages 12 and older. The survey found that 40% of parents said that either their child had already gotten at least one dose or would be getting one soon.

But parents of younger children were notably more guarded, with only about a quarter expressing a willingness to get their children vaccinated as soon as the shots become authorized for them.

The finding suggests that efforts to protect as many young students as possible from COVID-19 by the start of the school year could face barriers.

While public health experts welcomed the continuing improvement in vaccination rates, they noted that it meant the pool of the most willing adults was shrinking.

"At this point, there's almost no low-hanging fruit, but there's a path toward a slow-but-steady increase in vaccination rates through improved access, information, persuasion and incentives," said Drew Altman, the president and chief executive of the Kaiser Family Foundation.

President Joe Biden set a goal of 70% vaccine coverage for adults by July 4. Schaffner said he thought the goal was possible. "We have to work harder," he said.

The authors of the survey said the goal was realistic, because in addition to 62% of adults who had received at least one dose, another 4% said they wanted the shot as soon as possible, and still another 4% — representing a third of the "wait-and-see" group — said they had scheduled an appointment or intended to do so within three months.