Study Finds That 15% of US Children Get Vaccines Outside of Recommended Ages

Vaccinated children who received their vaccines earlier or later than recommended may not be fully protected, according to a study out of the University of Montana and Kaiser Permanente Colorado. The study, “Invalid Vaccine Doses Among Children Ages 0-35 months: 2011-2020,” publishes in the February 2025 Pediatrics (published online Jan. 10). Researchers used data compiled from the National Immunization Survey-Child from 2011 through 2020, which tracks immunization data for children aged 19 to 35 months, and found that over 15% of US children received an invalid vaccine. The term describes a vaccine given outside the recommended vaccine window as set by U.S. Advisory Committee on Immunization Practices guidelines. Vaccines given outside these recommendations may leave patients vulnerable, according to authors. The study tracked 10 vaccines including those that combat serious illnesses like measles and diphtheria. Some of the invalid doses occurred because children were vaccinated too early, according to guidelines. The study found of those children, nearly 45% ended up receiving additional vaccines and completed their series with valid doses. The percentage of children who received an invalid vaccine decreased over time, which may be due to improvements in technology that helps providers recommend the right vaccines at the right ages.  Authors recommended that providers provide families with accurate vaccine schedule information. They also suggest equity-based national and state investments in immunization information systems and clinical support technology in all settings where children receive vaccines.

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The American Academy of Pediatrics is an organization of 67,000 primary care pediatricians, pediatric medical subspecialists and pediatric surgical specialists dedicated to the health, safety and well-being of infants, children, adolescents and young adults.