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CNN  — 

Data published Thursday by the US Centers for Disease Control and Prevention shows that vaccination rates for three childhood vaccines fell in kindergartners in the 2020-21 school year compared with the 2019-20 school year, a “concerning” finding that may lead to more infections, a CDC immunizations expert said.

In the most recent school year, kindergartners had a 93.9% vaccination rate for measles, mumps and rubella (MMR), 93.6% for diphtheria, tetanus and acellular pertussis, and 93.6% for varicella.

“Compared with the 2019-20 school year, vaccination coverage decreased by approximately one percentage point for all vaccines,” the CDC researchers wrote.

The rate of children with a vaccine exemption remained similar to the rate in 2019-20: 2.5%.

“Although 2.2% of kindergartners had an exemption from at least one vaccine, an additional 3.9% who did not have a vaccine exemption were not up to date for MMR,” the researchers said.

Dr. Shannon Stokley, deputy director of the CDC’s Immunization Services Division, called the results “concerning.”

“Today’s findings support previous data showing a concerning decline in childhood immunizations that began in March 2020,” she said.

“We are concerned that missed routine vaccinations could leave children vulnerable to preventable diseases like measles and whooping cough, which are extremely contagious and can be very serious, especially for babies and young children.”

Results were compiled from data reported to the CDC by immunization programs in 47 states and the District of Columbia, covering more than 3 million children. Exemption data was available in 48 states and DC, and data on children in a vaccines “grace period” was available in 28 states.

“Nonexempt undervaccinated students often attend school while in a grace period or are provisionally enrolled; in many states, these policies were expanded either formally or informally during the 2020-21 school year,” the researchers wrote.

The study authors pointed to several possible connections between this data and the Covid-19 pandemic, including reduced access to appointments and reduced ability to collect data on vaccination rates.

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“During the 2020-2021 school year, national vaccination coverage among kindergarten children dropped from 95% to over 94%. This might not sound like much, but it amounts to at least 35,000 more children across the United States that entered kindergarten without documentation of complete vaccination against common diseases like measles, whooping cough and chickenpox,” Dr. Georgina Peacock, head of the CDC’s Immunization Services Division, said Thursday.

Peacock added that overall kindergarten enrollment dropped by about 10%, meaning those children may not be up to date, as well.

“With most schools back to in-person learning, extra effort is needed to catch up children who missed vaccines and to maintain high levels of routine childhood vaccination and equitable coverage to help protect children, their families and their communities against vaccine preventable diseases,” she said.