Researchers identified clusters of underimmunized children in northern California.
To identify pockets of underimmunization and vaccine refusal, the researchers used sophisticated spatial analysis software to review the records of 154,000 Kaiser Permanente Northern California members between birth and 3 years old.
The Centers for Disease Control's immunization schedule a minimum of 17 injections during a child's first two years, including vaccinations for "hepatitis A and B, diphtheria, tetanus, pertussis, influenza, polio, measles, mumps, rubella and pneumococcal virus."
"This research confirms anecdotal reports of underimmunization clusters," said Tracy A. Lieu, MD, MPH, the study's lead author, a Kaiser Permanente pediatrician, and director of the Kaiser Permanente Division of Research. "In addition, we found clusters in places we hadn't anticipated."
The findings could be used to identify areas that require more immunization outreach.
"Everyone in the Kaiser Permanente health care system has access to vaccines, and since childhood vaccination is covered by insurance, financial barriers are not an issue," Dr. Lieu said. "Our findings raise awareness that there may be communities where parents have more vaccine hesitancy and may be interested in more information or more in-depth conversations with their children's doctors."
Underimmunization rates ranged from 18 percent to 23 percent within clusters and was at about 11 percent outside of clusters. Vaccine refusal ranged from 5.5 percent to 13.5 percent within clusters, compared with 2.6 percent outside clusters.
"Kaiser Permanente's electronic medical record system is among the richest in the world," Dr. Lieu said. "This is the first time that spatial analysis techniques have been applied to real-time vaccine data."
The findings were published in a recent edition of the journal Pediatrics and is part of a larger study on parent preferences and vaccination funded by the Patient-Centered Outcomes Research Institute.
