Students head to class this month in Thornton, Colo. Infectious disease experts say the decline in vaccination rates against childhood diseases during the pandemic has increased the potential for outbreaks of diseases once largely vanquished in the United States.

Caption

Students head to class this month in Thornton, Colo. Infectious disease experts say the decline in vaccination rates against childhood diseases during the pandemic has increased the potential for outbreaks of diseases once largely vanquished in the United States. / MediaNews Group/The Denver Post via Getty Images

As she does ahead of every school year, Karen Schwind and the team of school nurses she manages in the New Braunfels Independent School District in central Texas spent a lot of time checking every student's immunization records against the state's database. The nurses also checked with parents and doctors' offices to ensure all students had received their required shots for measles, mumps, diphtheria, meningitis and other childhood diseases before classes started.

"We start notifying parents in the winter — like January, March and then again in May," says Schwind, whose district has 15 K-12 schools.

But recently, just a week before school was set to begin, Schwind estimated about 15% of children in her district were still missing at least one of those shots. COVID-19, she says, has complicated routine childhood vaccinations in a number of ways.

"Many clinics that give routine vaccines have been converted to giving COVID vaccine," Schwind says. "So in many places, the availability of the routine vaccines may not be the usual spot." Some families moved, or remained in online school all of last year, making it easier to overlook the state's vaccine requirements. And, Schwind says, in recent years, a growing number of parents have been applying for exemptions, citing religious, medical or philosophical reasons.

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According to the National Foundation for Infectious Diseases, similar patterns are playing out across the country, leaving infectious disease experts worried about the potential for outbreaks of illnesses that were once largely vanquished in the United States. Even modest declines in vaccination rates can compromise immunity within a community, as was seen during a big measles outbreak in the New York City area in 2018-2019.

The foundation's research, released this month, shows the number of doses given of recommended childhood vaccines has dropped below pre-pandemic levels — down by as much as 6% to 18%, depending on the vaccine or the age group. Babies and young children have been somewhat more likely to stay on schedule with most of their recommended vaccinations during the pandemic, the foundation's data shows, in comparison with adolescents and teens. But every age group is behind.

For example, the number of doses of Tdap vaccine — boosters given to kids ages 11 and up to prevent tetanus, diphtheria and pertussis — has dropped 16.7% since 2019. And orders for shots containing measles vaccine are down 18.2%.

"I've been trying to shout it from the rooftops," to get parents to take their kids in for routine vaccines, says Dr. Sean O'Leary, professor of pediatrics at the University of Colorado School of Medicine and vice chair of the Committee on Infectious Diseases for the American Academy of Pediatrics.

Many parents worry about COVID-19 and when they can vaccinate their kids against it, O'Leary notes. But he says, "Frankly, a lot of the diseases that we vaccinate kids for are more severe in children than COVID, and so the last thing we want as we reenter the school year is outbreaks of these other vaccine-preventable diseases."

Schwind, the Texas school nurse coordinator, says she and her staff are drawing a hard line in their school district: "We say no shots, no school," she says, meaning the schoolchildren who've missed shots will be flagged and the kids returned to their parents, who must take them to get the shots before they can return to class.

But in many schools across the U.S., school nurses don't keep tabs on students' vaccine status, says Linda Mendonca, president of the National Association of School Nurses. Her group's research shows a quarter of schools don't even have a nurse on staff — so it's unclear who's keeping tabs.

"I don't know who does it, honestly," Mendonca says of those schools. "Maybe the school secretary might keep track of records when they come in to school or something. But do they follow up with it? Do they understand what they're missing?"

William Schaffner, a professor of infectious disease at Vanderbilt University, calls the U.S. childhood vaccination programs a big success in public health, but he fears this year could see a big backslide in immunity against diseases such as mumps, meningitis, measles or others that had been under control.

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"We've seen that movie before with measles a couple of years ago," he says, when outbreaks across the country, spanning Washington state to Texas and New York registered the highest rates of measles cases since the disease had been eradicated in the U.S. in 2000. The disease traveled quickly within pockets of the population where vaccination rates ran low.

When vaccination rates fall below herd immunity levels, diseases such as measles or mumps or rubella — which are more common outside the U.S. — become a threat that's "only a plane ride away," Schaffner says.

Schaffner, who is 84, says such outbreaks were far more common decades ago. For most of his childhood, he says, he remembers polio kept a lid on his social life. Parents lived with the daily fear of the illness crippling or killing their children. "Couldn't go to swimming pools, couldn't go to movies," he says of his grade-school years through high school. It wasn't until he was in college that a vaccine for polio became available.

"Children lined up for blocks, were vaccinated and got little buttons like those campaign buttons that said they were a polio pioneer," Schaffner says, and all that helped eradicate the disease in the United States.

But Schaffner says that many people today didn't live through that era, so some parents may not feel as much urgency about getting their children those missed shots.

"There is not the knowledge and therefore not the respect or the fear of these childhood diseases," he says.

Schaffner says he hopes it won't take a resurgence of a horrible illness among children to remind people how important it is to keep up with those immunizations.

NPR's Pien Huang contributed to this report.

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