January 2025 Study Finds Children Ages 0 to 35 month Received at Least One Invalid Vaccine Dose
A January 2025 study from researchers in Montana and Colorado found that 15.4% of children ages 0 to 35 months received at least one invalid vaccine dose. The study looked at National Immunization Survey-Child data of 161,187 children between 2011 and 2020.
The most common invalid dose was for a 3-dose rotavirus vaccine with the first dose being administered after the maximum age. Children who moved across state lines were also more likely to have invalid vaccine doses.
Here’s why this is so important right now: the study also found that nearly one in four (24.4%) children who received an MMR vaccine between 6 and 11 months (likely due to travel to endemic areas) failed to receive a valid dose after 12 months. Given that the U.S. is on track for record numbers of measles cases this year (110 cases reported in 2025 so far, compared to 285 cases in all of 2024), it may be worth reminding clinicians of the importance of ensuring their patients receive a valid dose after 12 months of age.