For generations of most American families, getting children vaccinated was just something to check off on the list of back-to-school chores. But after the ferocious battles over Covid shots of the past two years, simmering resistance to general school vaccine mandates has grown significantly. Now, 35 percent of parents oppose requirements that children receive routine immunizations in order to attend school, according to a new survey released Friday by the Kaiser Family Foundation.

All of the states and the District of Columbia mandate that children receive vaccinations against measles, mumps, rubella and other highly contagious, deadly childhood diseases. (Most permit a few limited exemptions.)

Throughout the pandemic, the Kaiser foundation, a nonpartisan health care research organization, has been issuing monthly reports on changing attitudes toward Covid vaccines. The surveys have showed a growing political divide over the issue, and the latest study indicates that division now extends to routine childhood vaccinations.

Forty-four percent of adults who either identify as Republicans or lean that way said in the latest survey that parents should have the right to opt out of school vaccine mandates, up from 20 percent in a prepandemic poll conducted in 2019 by the Pew Research Center. In contrast, 88 percent of adults who identify as or lean Democratic endorsed childhood vaccine requirements, a slight increase from 86 percent in 2019.

The survey found that 28 percent of adults overall believed parents should have the authority to make school vaccine decisions for their children, a stance that in the 2019 Pew poll was held by just 16 percent of adults.

The shift in positions appears to be less about rejecting the shots than a growing endorsement of the so-called parents’ rights movement. Indeed, 80 percent of parents said that the benefits of vaccines for measles, mumps and rubella outweighed the risks, down only slightly from 83 percent in 2019.

“The talking point that has been circulated is the concept of taking away parents’ rights,” said Dr. Sean O’Leary, chairman of the American Academy of Pediatrics’ committee on infectious diseases. “And when you frame it that simply, it’s very appealing to a certain segment of the population. But what about the right to have your children be safe in school from vaccine-preventable diseases?”

Still, Dr. O’Leary said that he wasn’t overly worried that school vaccine mandates would be lifted but that the growing embrace of parents’ rights might further slow compliance with state-required immunization schedules, a timeline that has long been endorsed by pediatricians.

“We know a lot of kids missed their vaccines during the pandemic, not because they were refusing, but because, for many reasons, people weren’t going to the doctor,” he said. “And we do have a global dip in vaccine coverage. So this is not a time to be considering a rollback of these laws.”

The latest survey was based on interviews with a nationally representative sample of 1,259 adults and was conducted from Nov. 29 through Dec. 8.

It showed disappointing rates of uptake of the latest Covid booster, a “bivalent” shot that targets both the original coronavirus and the Omicron variant and has been available since September. Just four in 10 adults said they had either gotten the booster or intended to do so. Among those 65 and older — the age group at the highest risk — about one in four said they had been too busy to get it or hadn’t found the time to do so.

Even among adults who had received previous Covid vaccines, the survey found that more than four in 10 said they felt they did not need this latest shot.

Only about a third of respondents said they personally feared getting very ill from Covid, though half expressed concerns in general about rising rates of Covid this winter. About two-thirds of Black and Latino adults were apprehensive about Covid rates, compared with about four in 10 white adults.

The survey also found that about half of parents worried that their children could fall sick this winter from Covid-19, the flu or R.S.V. (respiratory syncytial virus), a sign that Covid-19 was increasingly becoming normalized in the public’s perception and joining the landscape of seasonal illnesses.