April 14, 2011

Study examines safety of childhood vaccinations

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Thomas Morgan, M.D., examines Marieluz Tomas-Francisco while her mother, Alicia Francisco Diego, holds her. (photo by Daniel Dubois)

Study examines safety of childhood vaccinations

Vanderbilt investigators have found that childhood vaccinations do not harm children with urea cycle disorders, a type of inborn errors of metabolism (IEM).

“Our study is one of the first to take a group that everyone would agree is going to be medically fragile and look at vaccines in this sub-group,” said Thomas Morgan, M.D., a clinical geneticist and assistant professor of Pediatrics at Vanderbilt.

“We showed there is no association between vaccination and the illnesses these vulnerable children experience,” Morgan said.

The impetus for the study, published this week in Pediatrics, was the case of Hannah Poling, a 2-year-old girl from Athens, Ga. Shortly after receiving several vaccines, Poling fell ill and her behavior regressed. The chatty toddler began exhibiting some classic behavioral signs of autism.

A physician's group for the Department of Health and Human Services determined Hannah's IEM — in her case a mitochondrial disorder — made her vulnerable to injury from vaccination. The family received more than $1 million in compensation for her injuries.

The case led to widespread concern than special populations of children might be at risk from vaccination.

Morgan's study examined children with a group of IEM called urea cycle disorders. Through the Urea Cycle Disorders Consortium, 169 children were enrolled and 74 cases were closely examined in which children had experienced both vaccination and an IEM-related illness serious enough to require hospitalization.

IEMs are known to trigger serious side effects from stress on the body such as illnesses.

“We looked back from each child's hospitalization seven and even 21 days before the illness and found no association with vaccinations,” Morgan said.

He points out all children with IEMs are more vulnerable than those without such disorders to the illnesses the vaccines protect against. He hopes this study will help physicians and parents feel more comfortable providing vaccines to children with IEMs.

“I would hope that people who are skeptical about vaccines will see we take the issue seriously enough to actually study it. That's what science does is provide information without having to rely on opinion,” Morgan said.

Morgan said since Poling has a different type of IEM, vaccine safety should be studied in each of these disorders. He said this is the first study of its kind to show that children with an IEM are not harmed by vaccines.

Other contributors to the article include Cameron Schlegel, a fourth-year School of Medicine student who worked on the study as part of an Emphasis Project. Kathryn Edwards, M.D., director of the Vanderbilt Vaccine Research Program; Teresa Welch-Burke, R.N., B.S.N.; Yuwei Zhu, M.D., M.S.; and Robert Sparks are also contributors. Marshall Summar, M.D., former professor of Pediatrics and Molecular Biophysics at Vanderbilt, who now serves as chief of Genetics and Metabolism at Children's National Medical Center in Washington, D.C., is senior author.

Funding for the study was supplied by the Centers for Disease Control and Prevention and from the National Institutes of Health.