August 25, 2011

New IOM study probes long-term impact of vaccines

New IOM study probes long-term impact of vaccines

A report released Thursday by the Institute of Medicine (IOM) 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 Ellen Wright Clayton, M.D., J.D., professor of Pediatrics and Law and director of the Center for Biomedical Ethics and Society, looked at scientific evidence about the potential risks of vaccines covered by the Vaccine Injury Compensation Program.

Ellen Wright Clayton, M.D., J.D.

Ellen Wright Clayton, M.D., J.D.

The analysis spanned more than 1,000 research articles and concluded that few health problems are caused by or clearly associated with vaccines.

"With the start of the new school year, it's time to ensure that children are up to date on their immunizations, making this report's findings about the safety of these eight vaccines particularly timely," Clayton said.

“The findings should be reassuring to parents that few health problems are clearly connected to immunizations, and these effects occur relatively rarely. And repeated study has made clear that some health problems are not caused by vaccines,” Clayton said.

The report, “Adverse Effects of Vaccines: Evidence and Causality,” was not intended to answer the question, “are vaccines safe?” committee members noted, and where the committee has found evidence of a causal relationship, it does 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 include 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.

It also reported indicative though less clear data on associations between specific vaccines and four other effects, such as 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, there is too little evidence, 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 Vaccine Injury Compensation Program.