Vaccinating Toddlers Too Early, Too Late Has Decreased Over Time

Vaccine doses given to U.S. toddlers outside the recommended age or timing intervals have decreased over time, but still don’t complete the vaccine series for many children, researchers found.

In an analysis of CDC immunization data from 2011 through 2020, 15.4% of children ages 35 months and younger had an invalid vaccine dose, defined as younger than the minimum age, sooner than the recommended interval between vaccinations, or older than the maximum age, reported Alexandria Albers, MPH, MS, of the University of Montana in Missoula, and colleagues in Pediatrics.

However, the percentage of tots with an invalid dose decreased from 16.9% in 2011 to 12.5% in 2020 (OR 0.98 for survey year, 95% CI 0.97-0.99). And the proportion who received extra doses and completed the series increased over that period from 29.5% in 2011 to reach 52.9% in 2020 (OR 1.1 for survey year, 95% CI 1.07-1.12).

When kids are dosed in an invalid way, the U.S. Advisory Committee on Immunization Practices (ACIP) recommends repeating vaccinations to meet guidelines, Albers and colleagues noted. “Invalid doses that are not repeated may leave children vulnerable to VPDs [vaccine-preventable diseases] and contribute to lowered disease protection in communities.”

There are tools to help bring vaccine administration within guidelines, the group added, pointing to the CDC’s Clinical Decision Support for Immunizations (CDSi) technology that can be integrated into electronic health and other systems to help providers make accurate recommendations at the point of care.

“The demonstrated reduction of invalid vaccination doses over time, as well as improved ‘catch-up’ vaccination rates after invalid doses over time, offer hope that increasingly robust electronic health records and statewide vaccination registries are working,” wrote David Bundy, MD, MPH, of the Medical University of South Carolina in Charleston, in commentary accompanying the study in Pediatrics.

“Implementation scientists frequently extol: ‘Make it easy to do the right thing and hard to do the wrong thing,'” he added. “With increased collaboration and coordination among patients/families, pediatric providers, vaccine manufacturers, and the Advisory Committee on Immunization Practices, much opportunity remains to make it easier to deliver the right vaccine to the right child at the right time.”

Further findings of the study by Albers and colleagues included that, among all children, the most common series with an invalid dose was the three-dose rotavirus vaccine (4.4%), followed by the three-dose Haemophilus influenzae type b vaccine (3.3%), the hepatitis A vaccine (2.3%), and the hepatitis B vaccine (2.1%).

Two of the most common reasons doses were invalid were receiving the first rotavirus vaccine dose after the maximum age of 105 days (3.1%) and the third hepatitis B vaccine dose before the minimum age of 164 days (1.3%).

Overall, receiving at least one invalid dose was associated with a child having three or more providers (adjusted OR 1.5, 95% CI 1.2-1.8) and having moved from a different state (aOR 1.5, 95% CI 1.4-1.6). Additionally, children who received all vaccinations at hospital-owned facilities rather than a private clinic had lower odds of receiving an invalid dose (aOR 0.8, 95% CI 0.7-0.9).

Albers and colleagues utilized provider-verified vaccine records in the CDC’s NIS-Child database to complete their study. Among the 161,187 children ages 0 to 35 months included in the analysis, 30% were 19 to 23 months, 33.4% were 24 to 29 months, and 36.2% were 30 to 35 months.

A little less than half were female. In terms of demographics, 27.1% were identified as Hispanic, 47.1% as non-Hispanic white only, 12.9% as non-Hispanic Black only, and 12.9% as non-Hispanic and not white or Black only, or as multiple races.

Limitations related to NIS-Child data included the possibility that invalid vaccinations may have been due to incorrect documentation as well as declining survey response rates, Albers and colleagues noted.

Additionally, although Albers and colleagues noted they suspected clinics with CDSi technology and reminder or recall systems had fewer invalid vaccinations and more children revaccinated with valid doses, they were not able to verify this through NIS-Child data.