The committee acknowledges the evidence that reducing vaccine coverage is associated with increases in vaccine-preventable disease and found only inconsistent and anecdotal evidence to imply that the recommended immunization schedule is not safe. Furthermore, existing systems for the detection of adverse events provide confidence that the existing childhood immunization schedule is safe, and the committee recognizes that the federal government invests considerable resources to ensure vaccine safety. Nevertheless, some stakeholders have suggested that further work is warranted, such as a comparison of vaccinated children with unvaccinated children or children receiving immunizations on alternative immunization schedules.

The committee supports the National Vaccine Advisory Committee Safety Working Group statement that “the strongest study design, a prospective, randomized clinical trial that includes a study arm receiving no vaccine or vaccine not given according to the current recommended schedule, would be unethical and therefore cannot be done” (NVAC, 2009, p. 38). In Chapter 6, the committee presents the formidable ethical and feasibility problems associated with the conduct of randomized controlled trials of children who receive all recommended immunizations and children who receive none of them and randomized controlled trials of children who receive all recommended immunizations and children who receive the recommended immunization on an alternative schedule. There are very low observed rates of adverse events with vaccination, which is another factor sffecting feasibility of a randomized controlled trial. Because of these problems, the committee concludes that a randomized controlled trial comparing the recommended schedule with any alternative schedule would be unethical and infeasible and could increase the risk of vaccine-preventable diseases in individuals and in the community.

Furthermore, the committee found that a trial of a modified version of the ACIP schedule—one that would disperse the timing of vaccinations so that children are visiting health care professionals more often but receiving fewer shots at each visit—would be ethical; however, it would add substantial costs to both parents and providers and, moreover, may be unacceptable to insurers if its effectiveness—measured as a decreased rate of adverse safety outcomes—was negligible. This modified schedule would provide immunizations within the time intervals approved by ACIP and would address the concern about immunization with too many vaccines at one office visit, but the committee did not view this option to be feasible for study.

In light of the ethical and feasibility requirements and the available evidence, the committee concludes that new randomized controlled trials of the childhood immunization schedule are not justified at this time.

Recommendation 6-2: The Department of Health and Human Services should refrain from initiating randomized controlled trials of the childhood

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