Existing evidence suggests the childhood immunization schedule is safe, although research looking for potential safety concerns should continue, according to a report from the Institute of Medicine.
The 14 committee members who looked into the issue acknowledged that vaccines carry some risks -- like any medication or intervention -- but found that the benefits outweigh those concerns.
"In this most comprehensive examination of the immunization schedule to date, the IOM committee uncovered no evidence of major safety concerns associated with adherence to the childhood immunization schedule, which should help to reassure a diverse group of stakeholders," the report says. "Indeed, rather than exposing children to harm, following the complete childhood immunization schedule is strongly associated with reducing vaccine-preventable diseases."
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The report, sponsored by the U.S. Department of Health and Human Services (HHS), addressed the childhood immunization schedule established for children 6 and younger by the Advisory Committee on Immunization Practices. The schedule is designed to protect against 14 pathogens.
Although about 90 percent of children receive most of the recommended vaccines by the time they enter kindergarten, the remaining 10 percent either receive vaccines on an alternate schedule or do not receive any vaccinations at all.
In that latter group, parental concerns about vaccination and potential side effects are driven largely by the number of immunizations required in the first years of life. Children can receive as many as 24 immunizations before age 2, and as many as five shots in a single visit.
"In light of this, [HHS] asked the Institute of Medicine to identify research approaches, methodologies, and study designs that could address questions about the safety of the current childhood immunization schedule," the authors wrote, adding that "parents, providers, and public health officials agree that there has been insufficient communication between providers and parents about vaccine safety concerns."
Chaired by Ada Sue Hinshaw, RN, PhD, of the Uniformed Services University of the Health Sciences in Bethesda, Md., the committee -- which included experts in pediatrics, neurology, medical ethics, immunology, statistics, epidemiology, and public health -- reviewed the existing evidence base on the safety of the vaccine schedule and did not find evidence suggesting that it is unsafe.
"The committee's efforts to identify priorities for recommended research studies did not reveal an evidence base suggesting that the childhood immunization schedule is linked to autoimmune diseases, asthma, hypersensitivity, seizures, child developmental disorders, learning disorders or developmental disorders, or attention deficit or disruptive behavior disorders," the authors wrote.
They acknowledged, however, that existing research was not designed to evaluate the safety of the vaccine schedule in its entirety and that research should continue looking for potential safety concerns with the schedule, which could become more complex as new vaccines are developed.
The report pointed to existing data sources as the best options for monitoring vaccine safety. Those include the Vaccine Adverse Event Reporting System, the Vaccine Safety Datalink, and the Clinical Immunization Safety Assessment Network -- which are CDC projects -- and the FDA's Sentinel Initiative.
Newer systems, including the National Children's Study and the Post-Licensure Rapid Immunization Safety Monitoring (PRISM) program, could also provide useful information, according to the IOM authors.
The committee concluded that the best tool out of that group is the Vaccine Safety Datalink, which collects information on demographics, vaccination history, diagnoses, medical procedures, and outcomes from more than 9 million children and adults treated within nine managed care organizations.
Potential limitations of that data source, however, include a lower level of diversity in the study population when compared with the U.S. general population and potential difficulty in accounting for differences between children who adhere to the federal vaccine schedule and those who use an alternate schedule.
"Future federal research approaches should continue to fund and support the Vaccine Safety Datalink project to study the safety of the recommended immunization schedule," the authors wrote.
They ruled out randomized trials as a way to evaluate the safety of the vaccine schedule because, "although this is the strongest study design type, ethical concerns prohibit this study, as unvaccinated individuals and communities intentionally would be left vulnerable to morbidity and mortality."
Also, because fewer than 1 percent of all Americans refuse all vaccines, an observational study to compare vaccinated and unvaccinated children would have to very large -- prohibitively so -- to find meaningful differences in health outcomes, according to the report.