A rapidly growing measles outbreak in Columbus, Ohio — largely involving unvaccinated children — is fueling concerns among health officials that more parent resistance to routine childhood immunizations will intensify a resurgence of vaccine-preventable diseases.

Most of the 81 children infected so far are old enough to get the shots, but their parents chose not to do so, officials said, resulting in the country’s largest outbreak of the highly infectious pathogen this year.

“That is what is causing this outbreak to spread like wildfire,” said Mysheika Roberts, director of the Columbus health department.

The Ohio outbreak, which began in November, comes at a time of heightened worry about the public health consequences of anti-vaccine sentiment, a long-standing problem that has led to drops in child immunization rates in pockets across the United States. The pandemic has magnified those concerns because of controversies and politicization around coronavirus vaccines and school vaccine mandates.

More than a third of parents with children under 18 — and 28 percent of all adults — now say parents should be able to decide not to vaccinate their children for measles, mumps and rubella (MMR) to attend public schools, even if remaining unvaccinated may create health risks for others, according to new polling by the Kaiser Family Foundation, a health-care research nonprofit.

Public sentiments against vaccine mandates have grown significantly since the pandemic, said Jen Kates, a Kaiser senior vice president. A 2019 poll by the Pew Research Center found that less than a quarter of parents — and 16 percent of all adults — opposed school vaccination requirements.

The growing opposition stems largely from shifts among people who identify as or lean Republican, the Kaiser survey found, with 44 percent saying parents should be able to opt out of those childhood vaccines — more than double the 20 percent who felt that way in 2019.

Adam Moore, a father of three in the Detroit suburbs, said none of his children — 9, 12 and 17 and enrolled in private school — have received routine childhood immunizations, let alone vaccines for the coronavirus or flu. He values personal liberty and says the government has no right telling people what to do with their bodies.

“I find it a hard argument when the government says we’re all for individual liberty on abortion rights and all this other stuff, but when it comes to vaccinations, there’s no such thing as ‘my body, my choice,’” said Moore, 43, an account manager for a marketing company.

Moore, who describes himself as Republican-leaning, said he does not view childhood diseases such as measles and polio, which have resurfaced in recent years, as threats. But if the deadly Ebola virus were circulating, he said, he would want his children to get vaccinated.

Other parents who oppose school immunization mandates echo long-standing misinformation about vaccines that continue to spread via anti-vaccine groups.

Bianca Hernandez, a 37-year-old dog breeder in the Albuquerque metropolitan area, described concerns about the link between vaccine ingredients and autism, a view that has been extensively disproved. She said her two youngest children receive religious exemptions from school vaccination requirements.

Support for immunization mandates has held steady among Democrats, with 88 percent saying that children should be vaccinated to attend public schools because of the potential risk for others when they are not.

Overall, 71 percent of all adults still support school immunization requirements, compared with 82 percent in 2019.

“The situation about increasing negative sentiment about childhood vaccination is concerning, but in absolute terms, vaccines remain the social norm,” said Saad Omer, director of Yale’s Institute for Global Health and an infectious-disease expert who has studied vaccine hesitancy.

Anne Zink, chief medical officer for Alaska’s health department, said that even in a state with historically lower vaccination rates, childhood immunization rates have yet to return to their pre-pandemic levels. In the years before the pandemic, about 65 percent of Alaskan children 19 to 35 months old had completed their routine childhood immunizations. By the end of 2021, 46 percent had.

“I think there is more mistrust of the government, there’s more questioning of vaccines, and we’ve been having a harder time getting people vaccinated,” said Zink, who is also president of the Association of State and Territorial Health Officials.

A few weeks ago, Zink, an emergency room doctor, saw her first case of chickenpox when a young woman walked into the Mat-Su Regional Medical Center in Palmer covered in large, painful lesions. The woman said she and her family did not believe in vaccinations and told Zink she thought chickenpox no longer existed.

“I was like, ‘Well, it really doesn’t when all of us choose to get vaccinated, but you aren’t vaccinated, your family’s not vaccinated, and the people you hang out with are not vaccinated. Chickenpox has been spreading in your community, and now you’re really sick,’” Zink recalled.

In the past, Zink said, herd immunity would have protected the woman against such childhood diseases. But that protection has waned as anti-vaccine sentiment grows, she said.

To distance its push for vaccination from the current political narrative, the Alaska health department recently brought back images and language from a 1960s promotion for polio vaccination. The new social media campaign uses the vintage Wellbee cartoon and rocket — “Get a booster!” — to remind people that immunization has always been part of the country’s history.

It is too early to see the effects of eroding public support for school vaccination requirements on childhood immunization rates because federal data typically lag by about two years. During the pandemic, routine vaccination rates slipped because of school closures and because children were not going to the doctor.

The growing negative attitudes about school immunization requirements are troubling for health workers. Kentucky officials are urging that people get flu shots after six children — none of whom were vaccinated — died after contracting influenza. South Carolina officials had also promoted childhood vaccinations after two chickenpox outbreaks in March — the first since 2020 — affected nearly 70 people.

A case of paralytic polio in a New York man this summer prompted worry that low childhood immunization rates and rising vaccine misinformation could result in the disease’s resurgence, decades after vaccination had eliminated it in the United States.

“There is definitely a group of parents who have shifted their attitudes,” said Jennifer Heath, immunizations program coordinator for Minnesota’s health department who works on vaccine hesitancy and outreach. “Part of it is true attitude shift. But part is a disconnection to the primary care provider, the human being who’s telling you that vaccines are important.”

School vaccination requirements are among the most effective tools to keep children healthy. All states and the District of Columbia require children to be vaccinated against certain diseases, such as measles, polio and whooping cough, to attend public school. All states grant exemptions based on medical reasons; a growing number allow religious or philosophical exemptions.

D.C. also requires students 12 and older to be vaccinated against covid-19 but has delayed enforcing the mandate until the 2023-2024 school year. California has a pending statewide student coronavirus vaccine mandate that will not take effect until after July 2023. Nearly two dozen states have some form of ban against student coronavirus vaccine mandates.

The Centers for Disease Control and Prevention recommends children get two doses of MMR vaccine, with the first dose at 12 to 15 months, and the second dose between 4 and 6 years old. One dose of the vaccine is about 93 percent effective in preventing measles, one of the most infectious pathogens on the planet that can cause serious complications, including death. Two doses are about 97 percent effective at preventing the disease.

In the Ohio measles outbreak, only three of the 81 children had received a single dose of vaccine, according to state data. None were known to be fully vaccinated.

“I think some of these attitudes were here before the pandemic, and then we probably picked up some additional community members who were accepting of vaccines before but now maybe are more critical about vaccines as a result of what transpired with the coronavirus vaccine,” Roberts said.

Some of the cases occurred in Columbus’s large Somali community, the second-largest Somali population in the United States after the Minneapolis area, Roberts said. Parents have said they “intentionally delayed” giving their children the measles vaccine because of their fear of autism, she said, despite considerable research disproving any relationship between vaccines and autism. Those fears echoed similar concerns of parents in Minnesota’s Somali community during a 2017 measles outbreak that infected 75 children, mostly unvaccinated preschool kids.

Minnesota is also battling a new measles outbreak — 22 cases — as vaccine hesitancy around the MMR vaccine continues to be an issue, said Doug Schultz, spokesman for the Minnesota health department.

Officials are bracing for more cases in the coming weeks as families travel and gather indoors for the holidays. At least 29 of the Ohio children have been hospitalized, some so sick they required intensive care.

Most of the sickened children — 78 percent — are Black, 6 percent are Asian, 6 percent are White, and 4 percent are Hispanic, according to Columbus officials.

Because the measles virus is so contagious, an overall community vaccination rate of about 90 to 94 percent is needed to keep the virus from causing large outbreaks, according to infectious-disease experts. In the United States, nearly 91 percent of children have received at least one dose of the MMR vaccine by age 2. In the Columbus area, Roberts said, the measles vaccination rate is estimated at 80 to 90 percent, but health-care providers are not required to report data to Ohio’s vaccine registry.

Even if overall coverage in a community is high, measles can transmit easily in clusters of under-vaccinated or unvaccinated people. The Columbus outbreak began when one or two unvaccinated people traveled to countries where measles is still common between June and October and infected others in the community, Roberts said.

In recent years, many of the measles cases reported to the CDC have occurred in underimmunized, close-knit communities, where anti-vaccine misinformation has gained a foothold. In 2019, the United States reported the highest annual number of measles cases — 1,294 — in more than 25 years; three-fourths of those cases occurred among New York’s Orthodox Jewish communities. Outbreaks have also occurred among the Amish in Ohio and Eastern European groups in the Pacific Northwest.

After consulting with counterparts in Minnesota, health officials in Ohio have been working closely with the Somali community to increase vaccination uptake without stigmatizing them. Columbus public health workers have hosted vaccine clinics at a community center and a mosque and are conducting home visits to provide shots. They have also reached out to schools, day-care centers and grocery stores about the importance of vaccination.

The efforts appear to be making a difference.

Nationwide Children’s Hospital in Columbus recently saw a 20 percent increase in the number of parents seeking the MMR vaccine, Roberts said. The health department, too, has seen a small uptick in vaccinations.

“They are trickling in,” she said, “slowly but surely.”