IOM Supports Safety of Childhood Immunization Schedule

Damian McNamara

January 18, 2013

A new Institute of Medicine (IOM) consensus report supports the safety of the recommended immunization schedule for children from birth to age 6 years in the United States, citing evidence to dispel concerns that up to 24 immunizations by 2 years of age represents too many vaccinations too soon.

"Upon reviewing stakeholder concerns and scientific literature regarding the entire childhood immunization schedule, the IOM committee finds no evidence that the schedule is unsafe," the 14 expert authors write in a brief that accompanied the full report, "Childhood Immunization Schedule and Safety: Stakeholder Concerns, Scientific Evidence, and Future Studies," published online January 16, 2013.

"[T]his most comprehensive examination of the immunization schedule to date...should help to reassure a diverse group of stakeholders. Indeed, rather than exposing children to harm, following the complete childhood immunization schedule is strongly associated with reducing vaccine-preventable diseases," write Ada Sue Hinshaw, RN, PhD, chair of the IOM committee, and coauthors. Dr. Hinshaw is dean and professor of the Graduate School of Nursing at the Uniformed Services University of the Health Sciences in Bethesda, Maryland.

Specifically, the committee reviewed the medical literature and did not find any evidence base to suggest a link between the childhood immunization schedule determined by the Advisory Committee on Immunization Practices (ACIP) and specific medical conditions. They found no associations, for example, with autoimmune diseases, asthma, hypersensitivity, seizures, pediatric developmental disorders, learning disorders or developmental disorders, or attention deficit or disruptive behavior disorders.

An important consensus emerged in development of the report: A variety of stakeholders, including healthcare providers, parents, and public health officials, "share the sentiment that there is insufficient communication between providers and parents about the schedule's safety." As a result, the committee suggests improved communication between health officials and parents to clarify misconceptions, build trust, and ensure any concerns continue to be addressed.

Single Database Best for Future Research

At the same time that the IOM committee was validating the safety of the immunization schedule, they were also charged with determining the best type of research to promote going forward.

The committee concluded that randomized controlled trials, prospective observational studies, and long-term studies (following infants to adulthood) are not feasible or practical for comparing vaccinated vs unvaccinated children, despite calls from some groups for this type of research.

Instead of initiating new study designs, the experts determined that secondary analyses of existing vaccine safety databases is the best approach. The Centers for Disease Control and Prevention maintains 3 major postmarketing vaccine surveillance systems, but the report authors recommend that researchers focus on the enhancement and evaluation of a single system in particular: the Vaccine Safety Database.

Although some parents choose an alternate schedule for immunization of their children, such as delaying 1 or more vaccinations, the Vaccine Safety Database should be amended to track any meaningful difference between children who strictly adhere and those who do not strictly adhere to the recommended schedule, according to the IOM report. The experts also called for safety monitoring studies to include more diversity to more closely reflect the diverse demographics of the US population.

"The committee believes that although the available evidence is reassuring, studies designed to examine the long-term effects of the cumulative number of vaccines or other aspects of the immunization schedule have not been conducted," the report states.

The committee also recognized that although more than 90% of children entering kindergarten are immunized with recommended vaccines in accordance with the ACIP schedule, "medical exemptions are allowed in all states, and almost all states allow immunization exemptions for people who have religious beliefs against them. Furthermore, 20 states permit exemptions for those who object to immunizations because of personal, moral, or other beliefs."

The committee addressed the public health dangers associated with vaccine delays and exemptions by pointing out parents who delay or refuse to immunize their children have "already contributed to outbreaks of disease across the United States that pose a risk to the health of many people, particularly those with compromised immune systems."

The US Department of Health and Human Services sponsored the report. The authors have disclosed no relevant financial relationships.

Childhood Immunization Schedule and Safety: Stakeholder Concerns, Scientific Evidence, and Future Studies. National Academies Press. Published online January 16, 2013. Full text