Childhood Immunizations

Institute of Medicine Report Finds Childhood Immunization Schedule Safe

Pediatrics Update
Brief Summaries for Clinical Practice

What do you say to parents who express concern about the number of vaccinations their child receives at each visit and request flexibility, such as delaying one or more immunizations? A new report from the Institute of Medicine (IOM) underscores the safety of the current childhood immunization schedule prepared by the US Advisory Committee on Immunization Practices (ACIP).1 This report is the most comprehensive examination of the immunization schedule to date.

About 90% of American children receive most recommended childhood vaccines by the time they enter kindergarten.1 However, some parents choose to spread out their children’s immunizations over a different time frame than that recommended by the ACIP schedule—and a much smaller number object to having their children immunized at all. Their concerns stem in part from fears about the frequency of vaccinations and the potential adverse effects of the vaccines themselves.


In response to these concerns, an IOM committee reviewed the scientific literature on childhood immunizations. The committee found “no evidence that the schedule is unsafe.”1 In particular, there were no data that showed the current immunization schedule was associated with learning or developmental disorders, seizures, autoimmune diseases, asthma, or hypersensitivity. The committee concluded that “rather than exposing children to harm, following the complete childhood immunization schedule is strongly associated with reducing vaccine-preventable diseases.”1

Studies have repeatedly shown the health benefits associated with the recommended schedule, including fewer illnesses, deaths, and hospital stays. Every new vaccine is tested for safety and evaluated in the context of the entire schedule before it is added. Moreover, the systems designed to detect possible harmful effects of immunization have worked well at discovering occasional problems with individual vaccines, such as intussusception linked to a now-discontinued rotavirus vaccine.


The Vaccine Safety Datalink (VSD) is the best available tool for exploring questions about the immunization schedule should the need arise, the IOM committee concluded. This database contains the immunization histories of more than 9 million children and adults covered by nine participating managed care organizations. Researchers can identify individuals who were vaccinated according to alternative schedules as well as any diagnoses, medical procedures, and outcomes they have experienced. The VSD also contains data on race, age, gender, and other factors that might affect participants’ health.

However, VSD tracks people from only eight states and looks at a smaller percentage of low-income and minority persons than is in the US population as a whole. Moreover, the usefulness of the VSD depends on the continuing involvement of participating health plans.

Newer data collection and surveillance systems offer great potential to monitor rare adverse events that may be associated with the childhood immunization schedule, the IOM committee said. When fully implemented, the Sentinel Initiative program being developed by the US Food and Drug Administration (FDA) to monitor the safety of approved drugs and other medical products will complement existing passive vaccine surveillance systems. FDA’s new Post-License Rapid Immunization Safety Monitoring Program is amassing a large amount of health data, offering the potential to analyze vaccine exposures and adverse events with a greater degree of statistical power.

Although randomized controlled trials are the gold standard for clinical research, such a trial cannot be safely and efficiently performed to compare health outcomes among vaccinated and unvaccinated or differently immunized children, the IOM committee concluded. Ethical concerns would prohibit this study because unvaccinated individuals and communities would be left vulnerable to morbidity and mortality.