Research Summary

What are the Factors Associated With Children Not Completing Their Multidose Vaccine Series?

Jessica Ganga

More than one in six children living in the United States initiated but did not complete all the doses required in a multidose vaccine series, according to a study conducted by a team of researchers.

“Most early childhood immunizations require three to four doses to achieve optimal protection. Our objective was to identify factors associated with starting but not completing multidose vaccine series,” the authors wrote.

Michels and colleagues used the 2019 National Immunization Survey-Child to evaluate data from children aged between 19 to 35 months (n = 16,365). The data was classified in one of three vaccination patterns: (1) completed the combined seven-vaccine series, (2) did not initiate at least one of the seven vaccine series, or (3) initiated all series, but did not complete at least one multidose series.

Of the total, the researchers found that 72.9% of children completed the combined seven-vaccine series, 9.9% did not initiate at least one series, and 17.2% initiated, but did not complete at least one multidose series. Further, approximately 8.4% of children required only one additional vaccine dose from one of the five multidose series to complete the combined seven-vaccine series.

The researchers noted the barriers that contribute to the patterns found, including: (1) moving across state lines, (2) number of children in the household, (3) lack of insurance coverage.

“Increased focus on strategies to encourage multidose series completion is needed to optimize protection from preventable diseases and achieve vaccination coverage goals,” the researchers concluded.



Michels SY, Niccolai LM, Hadler JL, et al. Failure to complete multidose vaccine series in early childhood. Pediatrics. Published online July 25, 2023. doi:10.1542/peds.2022-059844