Study: More Than One Third of Children at Risk From Delayed Immunization Schedules

February 24, 2020

By Priyam Patel

A collaborative group of investigators led by researchers at the Rollins School of Public Health recently conducted a study published in Pediatrics which found that more than one-third of US children are not following the Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) recommended early childhood immunization schedule. The researchers also examined vaccine adherence patterns and sociodemographic characteristics to evaluate their impact on children’s up-to-date immunization status. Allison Hargreaves was the first author on the study, with Allison Chamberlain, PhD, Laura Randall, and Robert Bednarczyk, PhD, also contributing from Rollins.

Using data from the 2014 National Immunization Survey, the researchers classified childhood vaccination patterns as “recommended”, “alternate”, and “unknown or unclassified,” before evaluating each pattern’s association with up-to-date vaccination status. The vaccine schedules and up-to-date status were classified based on ACIP-recommended vaccine administration, including rotavirus and hepatitis A, between birth and 19 months. The researchers used sociodemographic variables, vaccine pattern type, and up-to-date status to conduct analyses and create models to determine the associations between these factors.

The study found that about 63% of children follow the recommended pattern of vaccine adherence, and 58% of children were up-to-date with recommended immunizations by 19 to 35 months. About 37% of US children did not follow the recommended vaccine schedule, which was strongly associated with not being up-to-date on immunizations. The researchers also found that vaccine uptake differs based on sociodemographic characteristics such as socioeconomic status and race.

Previous vaccine uptake studies have typically examined vaccine coverage at 19-35 months, but this research highlights adherence patterns from 0-19 months of age. While vaccine coverage by 19 months is high, not following the recommended immunization schedule during the first 18 months can leave children vulnerable to preventable diseases. Also, previous research has focused on the CDC’s “up-to-date” vaccination status to calculate vaccine coverage, but this study expands on the CDC’s definition in order to depict a more comprehensive picture of compliance with the recommended vaccine schedule. The researchers hope that the information provided by this study will help to inform targeted interventions to promote vaccine schedule adherence, increase the number of US children who are up-to-date on immunizations, and minimize disease susceptibility.