A report released by the Institute of Medicine last September confirms the safety of eight vaccines studied by a committee of experts convened in 2009 to review epidemiological, clinical and biological evidence regarding adverse health events.
The committee—chaired by Vanderbilt’s Dr. Ellen Wright Clayton, the Craig–Weaver Chair in Pediatrics, professor of law, and director of the Center for Biomedical Ethics and Society—looked at scientific evidence regarding potential risks of vaccines covered by the National Vaccine Injury Compensation Program.
The analysis spanned more than 1,000 research articles and concluded that few health problems are caused by or clearly associated with vaccines. That conclusion was of such intense public interest that Clayton did a remarkable 54 media interviews the day of its release.
“The findings should be reassuring to parents that few health problems are clearly connected to immunizations, and these effects occur relatively rarely,” she says. “And repeated study has made clear that some health problems are not caused by vaccines.”
The report, “Adverse Effects of Vaccines: Evidence and Causality,” was not intended, as noted by committee members, to answer the question, “Are vaccines safe?” And where the committee did find evidence of a possible causal relationship, it did not make conclusions about the rate or incidence of these adverse events. For most analyses in the report, the evidence is inadequate to accept or reject a causal relationship, committee members said.
Vaccines studied included the varicella zoster vaccine; influenza vaccines; hepatitis B vaccine; human papillomavirus vaccine (HPV); tetanus toxoid-containing vaccines other than those containing the whole-cell pertussis component; measles, mumps and rubella vaccines; hepatitis A vaccine; and meningococcal vaccines.
Evidence showed no links between immunization and serious conditions that have raised concerns, including Type 1 diabetes and autism.
Committee members found convincing evidence of 14 health outcomes—including seizures, inflammation of the brain and fainting—that can be caused by certain vaccines, although these outcomes occur rarely. They also reported indicative, though less clear, data on associations between specific vaccines and four other effects, including allergic reactions and temporary joint pain.
Establishing a cause-and-effect relationship between an agent and a health outcome requires solid evidence, committee members said. In many cases of suggested vaccine-related adverse outcomes, too little evidence exists—or the available evidence offers conflicting results or is otherwise inadequate to draw conclusions.
The review, sponsored by the U.S. Department of Health and Human Services (HHS), will be used to help administer the National Vaccine Injury Compensation Program.