decide to delay or omit immunizations. Other parents express a general lack of confidence in U.S. government decisions about the safety and benefits of the childhood immunization schedule.

The committee understands that these parental concerns are an expression of concern and a way to care for their children’s health and well-being. However, the committee also recognizes that a delay or refusal to immunize their children has 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 committee’s review of the literature also focused on factors that affect public trust in vaccination campaigns and information on vaccines. Improved communication between public health authorities and parents will require improvements to the clarity of information as well as the building of trust and the use of a systematic approach to elicit public concerns. Further research into questions that parents seek to answer by use of the scientific methods of social, behavioral, and decision science is indicated.


The committee searched for, assembled, and summarized evidence on the association between the immunization schedule and specific health conditions that was already published in the peer-reviewed literature. The health outcomes that the committee chose to review were selected on the basis of an examination of the peer-reviewed literature, previous IOM vaccine safety studies, and public presentations at open meetings of this committee. The number of studies that addressed aspects of the immunization schedule varied; for some outcomes, several studies had examined the cumulative effects of vaccines and adjuvants or preservatives, whereas very few studies could be found for other outcomes.

The committee’s literature searches and review were intended to identify health outcomes associated with some aspect of the childhood immunization schedule. Allergy and asthma, autoimmunity, autism, other neurodevelopmental disorders (e.g., learning disabilities, tics, behavioral disorders, and intellectual disabilities), seizures, and epilepsy were included as search terms. Furthermore, the committee reviewed papers on immunization and premature infants.

In summary, few studies have comprehensively assessed the association between the entire immunization schedule or variations in the overall schedule and categories of health outcomes, and no study has directly examined health outcomes and stakeholder concerns in precisely the way that the committee was charged to address in its statement of task. No studies have compared the differences in health outcomes that some stakeholders questioned between entirely unimmunized populations of children and fully

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