Patches of low vaccination in the US are becoming bigger, riskier holes

By Deidre McPhillips, CNN

(CNN) — Opting out of childhood vaccines is becoming more common across most of the United States, leaving larger shares of the population vulnerable to preventable diseases like measles, which is continuing its record-breaking spread across the country.

Exemption rates for vaccines that are typically required to attend school have increased in more than half of US counties since the start of the Covid-19 pandemic, according to new research published Wednesday in the medical journal JAMA.

What’s driving the trend: nonmedical reasons for exemptions — often described as religious or personal beliefs. However, exemptions for medical reasons – among those who are immunocompromised, for example, or those who have a severe allergy to a vaccine component or – have remained stable.

“The science behind immunizations has not changed in the past five years,” said ​Dr. Jesse Hackell, a pediatrician in New York. He is the lead author of a policy statement from the American Academy of Pediatrics that says that nonmedical exemptions to school immunization requirements should be eliminated.

“What has changed is the politics and the misinformation behind the discussion,” Hackell said. “But the science about the immunizations — that they’re safe, that they’re effective, that they reduce disease, that they reduce morbidity and mortality – there are no changes in that science.”

In the new analysis, researchers compared the average rate of vaccine exemptions among kindergartners at the county level during a period before the Covid-19 pandemic to more recent years. Nearly 90% of counties had sufficient data to be included in the analysis. They found that the median rate of nonmedical exemptions increased from an average of 0.6% in 2010-2011 to more than 3% in 2023-2024, while medical exemptions remained stable.

About 53.5% of US counties saw nonmedical vaccine exemptions rise at least 1% when comparing between 2010-2020 and 2021-2024, and more than 5% — about 1 in every 20 counties — saw nonmedical exemptions rise at least 5% in that time.

According to the US Centers for Disease Control and Prevention, the increase in vaccine exemptions may be “due to an increase in vaccine hesitancy.” A survey of parents conducted by the agency in the summer of 2024 found that most supported vaccine requirements to attend school. But among those seeking an exemption, the most commonly reported reason – cited more than a third of the time – was a philosophical or personal belief objection to vaccination. Difficulty meeting school requirements by the deadline was also reported as a reason for exemption by about 23% of parents. Medical reasons were cited by more than a quarter of parents, but the CDC said that might include parents who consider concerns about vaccine safety or side effects as a “medical” reason to request an exemption.

Dr. Nathan Lo, an infectious disease physician and scientist with Stanford and author of the new research, says that small differences in vaccine coverage can make a big impact — and understanding local trends is important.

“When you look at national trends, or even state level trends, in many ways they’re very optimistic because they miss whole pockets of communities and counties where vaccine coverage may be low and vaccine exemptions may be high,” Lo said. “Really it’s those pockets that drive the outbreaks of vaccine preventable diseases that we see across the nation.”

Unvaccinated areas are growing

In Spartanburg County, South Carolina – the center of a large, ongoing measles outbreak – nearly 8% of children had nonmedical exemptions for vaccines that are required to attend school in 2024, up from 2% in 2014, the new research shows.

The South Carolina measles outbreak has doubled in size over the past week, with state health officials now reporting more than 400 cases. At least 400 others remain in quarantine after they were exposed to a known measles case without the protection of vaccination, and the state health department expects more cases to come from that group.

The outbreak has been growing rapidly since early October. Exposures have been reported at multiple schools, churches and other public locations over the past few months. The latest public exposures include the South Carolina State Museum in Columbia, which is one of the state’s most populous cities.

The state health department says that holiday activities — including school breaks, gatherings and travel — have contributed to the spread of the outbreak, particularly in areas with lagging vaccination rates.

“The (undervaccinated) pockets are all interconnected,” Lo said, through geographic proximity and the nature of our society. “When you think about the places with really large (vaccine exemption rates), I think the pockets are getting a little bit bigger and are becoming more numerous.”

The vast majority of measles cases in the current outbreak have been among children (92%) and nearly all have been unvaccinated with the measles-mumps-rubella (MMR) vaccine, according to data shared by the state health department.

Communities with particularly high exemption rates — and, therefore, lower vaccination rates — are most susceptible to a “localized epidemic” of preventable infectious diseases, Hackell said. But it raises the risk for others, too.

“If you’ve got a whole bunch of kids in one of these counties with high exemption rates who are getting sick and have the opportunity to travel the surrounding areas, even those counties with lower exemption rates are going to see a rise in cases,” he said. “You’ve got a lot more people around who can spread the diseases to people who may be susceptible.”

Multiple cases in North Carolina have been linked to family travel to Spartanburg County, South Carolina, and the New Mexico health department warned of possible measles exposure in Albuquerque from someone visiting from South Carolina.

Most parents choose vaccination

A handful of states, including California, Connecticut, Maine and New York, have passed laws that remove the option for nonmedical vaccine exemptions. The new research shows that counties in these states saw a decrease in overall exemptions, or essentially an increase in vaccine coverage. Florida, on the other hand, has recently moved to end all vaccine mandates in the state, including for children to attend school.

Experts say that legislative action is the only large-scale intervention that has been shown to effectively change vaccination trends. Instead, increasing vaccination coverage will depend more on individual conversations between families and their doctors and consistent messaging over time.

“The vast majority of parents in most places choose to immunize,” Hackell said. Nationally, 3.6% of kindergartners in the 2024-25 school year had an exemption for a required vaccine, federal data shows — but that means that more than 96% were vaccinated.

“A parent who chooses to vaccinate their child is not being careless or thoughtless or weird,” he said. “The social norm is to immunize and protect your child and, by extension, protect the children around them. The social norm is vastly in favor of immunizations, and that reflects the science.”

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