DENVER, January 21, 2013 — In a new study published today in JAMA Pediatrics (formerly Archives of Pediatrics and Adolescent Medicine), Kaiser Permanente researchers found that 49 percent of children ages 2-24 months did not receive all recommended vaccinations or did not get vaccinated according to the Advisory Committee on Immunization Practices schedule.

Kaiser Permanente researchers used the Vaccine Safety Datalink — a collaborative effort among the Centers for Disease Control and Prevention and nine managed care organizations — to analyze immunization records of 323,247 children born between 2004-2008. Data from immunization records helped illuminate the number of days each child was missing scheduled vaccines for any reason, including parents intentionally choosing not to vaccinate their children according to ACIP recommendations. Children who did not receive their vaccines on time were considered “undervaccinated.”

“While a large majority of parents in the U.S. choose to vaccinate their children, a growing number of parents are concerned about vaccine safety and choose to vaccinate their children according to alternative immunization schedules,” said lead study author Jason Glanz, PhD, a senior scientist at Kaiser Permanente’s Institute for Health Research. “The medical community doesn’t have a lot of data on these alternative schedules, so we are hoping the results from this study will open the door to more opportunities to examine their safety and efficacy.”

The study found the number of undervaccinated children increased significantly during the study period, and 1 in 8 undervaccinated children’s parents intentionally chose not to adhere to ACIP immunization guidelines. Alternative schedules either involve increasing the time between vaccinations or reducing the number of vaccinations in a single office visit, leaving children undervaccinated. Study findings also indicate undervaccinated children are less likely to visit their doctor’s offices and more likely to be admitted to hospitals, compared to their peers vaccinated under the standard schedule.

Kaiser Permanente can deliver transformational health research like this study in part because it has the largest private electronic health record system in the world. The organization’s integrated model and electronic health record system securely connect 9 million people, 611 medical offices and 37 hospitals, linking patients with their health care teams, their personal health information, and the latest medical knowledge. The Vaccine Safety Datalink project, which monitors immunization safety and addresses the gaps in scientific knowledge about any rare and serious events that occur following immunization, is enabled in part by Kaiser Permanente’s electronic health record.

Kaiser Permanente is committed to furthering understanding of vaccine effectiveness and safety, including patterns of vaccine refusal. Recent Kaiser Permanente studies found children of parents who refuse vaccines are nine times more likely to get chickenpox and 23 times more likely to get whooping cough than fully immunized children.