May 5, 2022 12:11 PM EDT

Anti-vaccine sentiments have been simmering in the U.S. since at least 1998, when the Lancet, a prestigious medical journal, published—and later retracted—a fraudulent paper falsely linking childhood vaccines to autism. They’ve grown even stronger in the past two years, thanks to disinformation about the COVID-19 vaccines. Though the development of the COVID-19 vaccines happened at an unprecedented pace, they’ve been rigorously tested, and have proven both safe and effective. Nevertheless, falsehoods about them—that the vaccines contained microchips, that they would alter the DNA of recipients or cause them to become magnetic—have spread.

Public-health experts feared that those groundless claims would exacerbate mistrust among people who already doubted vaccines or serve as a gateway into vaccine skepticism among people who previously had no such concerns. Now it appears those fears might have been well-placed. In April, the U.S. Centers for Disease Control and Prevention (CDC) published a study showing that during the 2020-2021 school year, rates of routine vaccinations among the nation’s 3.52 million enrolled kindergarteners fell below the 95% level necessary to ensure herd immunity. The average drop from the rates during the 2019-2020 school year was small, just over 1% for each of three vaccines. But CDC researchers say that is enough to allow viruses to gain a foothold in the overall community of kids, many of whom may be unable to be vaccinated for medical reasons.

The researchers cited multiple variables that might have contributed to reduced vaccination rates, including skipped well-child visits during the height of the pandemic and the shuttering of schools, most of which require vaccinations for students to attend. But anti-COVID-19 vaccine beliefs most likely played a part, many experts say.

“I think that segment of the community who’s already mistrusting of the medical community has been re-energized for sure,” says Dr. Gary Kirkilas, a Phoenix-area pediatrician and spokesman for the American Academy of Pediatrics. “We’ve had this politicization of the [COVID-19] vaccine that just leads to more mistrust.”

So far, the U.S. has been lucky that subpar vaccination rates haven’t yet triggered a rise in routine childhood illnesses. “We haven’t seen outbreaks, and that’s probably representative of the fact that families were staying home during the pandemic,” said Dr. Georgina Peacock, acting director of the CDC’s immunization services, and an author of the recent CDC study, at a press briefing when the findings were released. But now that most kids are back in classrooms, experts worry that epidemics like the national measles outbreak of 2019 are increasingly likely.

Growing anti-vaccine sentiments

California had long been a national leader in enforcing vaccine requirements to attend schools; in 2015, lawmakers there eliminated personal-belief exemptions for parents who did not want to get their children vaccinated. But recently, additional proposed bills to require all businesses to mandate COVID-19 vaccines for their employees, and to add COVID-19 to the list of vaccines for which personal belief exemptions for students are applicable, have not advanced in the state legislature.

Christina Hildebrand has a theory why. For years, she has been lobbying against California state legislation that mandates vaccination as a condition for attending public schools. Before the pandemic, she says, lawmakers were resistant to her arguments, and weary of her lobbying. But since the COVID-19 vaccines were released, Hildebrand says, they seem to be more receptive in the California State Assembly, in Sacramento. “I think it’s because prior to this, legislators didn’t have personal experience with the vaccine issue. Whereas now, every single legislator has had some experience.” She believes that the doubts people are feeling over the COVID-19 vaccine for kids (which studies have shown to be safe and effective) have spurred more people to rethink routine vaccinations in this age group.

That’s exactly what concerns experts like Dr. Gerald Harmon, president of the American Medical Association (AMA). “We’ve had three different pandemics,” he says. “The COVID-19 pandemic, the disinformation pandemic, and now the pandemic of distrust. So there is a substantial risk of giving more oxygen to the anti-vaxxer population.”

Falling vaccination rates

The recent CDC study looked at the change in vaccination rates from 2019-2020 to 2020-2021 for three routine childhood shots:

  • measles, mumps, and rubella (MMR), for which vaccination rates fell from 95.2% to 93.9%
  • diphtheria, tetanus, and acellular pertussis (DTaP), which fell from 94.9% to 93.6%
  • varicella, or chickenpox, which fell from 94.8% to 93.6%

Those seemingly small drops below the 95% threshold are troubling, especially when it comes to measles, which is so transmissible that even a point below the 95% herd immunity rate is enough to get the disease spreading widely among the unvaccinated. “Measles is an incredibly contagious childhood, which carries a serious risk of lifetime injury,” says Harmon. In some cases, kids who get measles can develop damage to the central nervous system as late as 10 years after the initial infection. Troubling as the national vaccine numbers are, they are far worse in some states. Maryland saw its vaccination rate plummet from an average of 95% for all three vaccines in the 2019-2020 school year to 87.6%, 89.7%, and 87.3% respectively for the MMR, DTaP, and varicella vaccines the following year. Wisconsin saw a 5% drop to about 87.2% for all three shots. The least-vaccinated state in the nation for this age group is Idaho, at just over 86% for all three jabs. That represents a 3% drop from 2019-2020.

Since the CDC last tallied childhood vaccination rates in 2021, schools have reopened—with mandates for vaccinations in place—and visits to pediatricians have increased after a sharp decline. In theory, those two factors mean that the vaccination numbers could recover, but Harmon and Kirkilas are not alone in worrying that the damage done by mistrust and misinformation regarding COVID-19 vaccines could have a lasting impact on the uptake of other vaccines. Indeed, “routine immunization rates have been slow to rebound,” said the American Academy of Pediatrics in January 2022.

Francesco Pierri, a postdoctoral student at the Polytechnic University of Milan and lead author of an April study published in Nature Scientific Reports that correlated COVID-19 vaccine misinformation posted on Twitter and negative attitudes in surveys about the shots, believes that the low childhood vaccination rates may well be tied to unfounded COVID-19 vaccine rumors.

“You can assume some spillover effect,” he says. “The activity around this kind of malicious content has increased, [leading to] an increase in the prevalence of misinformation of vaccines in general.”

Says Harmon, the AMA president, and a former Major General in the Air Force Reserve and the Air National Guard: “One of the things I learned in the military was that the way to overcome resistance is to maintain overwhelming competence. I take these vaccine-hesitant individuals and address them one on one. I try to answer their questions, to stay on the side of the science, and to not get emotional.” The most effective antidote for misinformation, he says, is more information—the genuine, scientific variety.

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Write to Jeffrey Kluger at [email protected].

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