The proportion of U.S. kindergartners exempted from school vaccination requirements has hit its highest level ever, 3%, U.S. health officials said Thursday.

More parents are questioning routine childhood vaccinations that they used to automatically accept, an effect of the political schism that emerged during the pandemic around COVID-19 vaccines, experts say.

Even though more kids were given exemptions, the national vaccination rate held steady: 93% of kindergartners got their required shots for the 2022-2023 school year, the same as the year before, the Centers for Disease Control and Prevention said in a report Thursday. The rate was 95% in the years before the COVID-19 pandemic.

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"The bad news is that it’s gone down since the pandemic and still hasn’t rebounded," said Dr. Sean O’Leary, a University of Colorado pediatric infectious diseases specialist. "The good news is that the vast majority of parents are still vaccinating their kids according to the recommended schedule."

All U.S. states and territories require that children attending child care centers and schools be vaccinated against a number of diseases, including, measles, mumps, polio, tetanus, whooping cough and chickenpox.

All states allow exemptions for children with medical conditions that prevents them from receiving certain vaccines. And most also permit exemptions for religious or other nonmedical reasons.

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In the last decade, the percentage of kindergartners with medical exemptions has held steady, at about 0.2%. But the percentage with nonmedical exemptions has inched up, lifting the overall exemption rate from 1.6% in the 2011-2012 school year to 3% last year.

Last year, more than 115,000 kindergartners were exempt from at least one vaccine, the CDC estimated.

The rates vary across the country.

Ten states — all in the West or Midwest — reported that more than 5% of kindergartners were exempted from at least one kind of required vaccine. Idaho had the highest percentage, with 12% of kindergartners receiving at least one exemption. In contrast, 0.1% had exemptions in New York.

The rates can be influenced by state laws or policies can make it harder or easier to obtain exemptions, and by local attitudes among families and doctors about the need to get children vaccinated.

"Sometimes these jumps in exemptions can be very local, and it may not reflect a whole state," said O’Leary, who chairs an American Academy of Pediatrics committee on infectious diseases.

Hawaii saw the largest jump, with the exemption rate rising to 6.4%, nearly double the year before.

Officials there said it’s not due to any law or policy change. Rather, "we have observed that there has been misinformation/disinformation impacting people’s decision to vaccinate or not via social media platforms," officials at the state’s health department said in a statement.

Connecticut and Maine saw significant declines, which CDC officials attributed to recent policy changes that made it harder to get exemptions.

Health officials say attaining 95% vaccination coverage is important to prevent outbreaks of preventable diseases, especially of measles, which is extremely contagious.

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The U.S. has seen measles outbreaks begin when travelers infected elsewhere came to communities with low vaccination rates. That happened in 2019 when about 1,300 measles cases were reported — the most in the U.S. in nearly 30 years. Most of the cases were in were in Orthodox Jewish communities with low vaccination rates.

One apparent paradox in the report: The national vaccination rate held steady even as exemptions increased. How could that be?

CDC officials say it’s because there are actually three groups of children in the vaccination statistics. One is those who get all the shots. A second is those who get exemptions. The third are children who didn't seek exemptions but also didn’t get all their shots and paperwork completed at the time the data was collected.

"Last year, those kids in that third group probably decreased," offsetting the increase in the exemption group, the CDC’s Shannon Stokley said.