Recommended Childhood Vaccines Safe for Children With Inborn Errors of Metabolism

Alice Goodman

November 04, 2009

November 4, 2009 (Philadelphia, Pennsylvania) — Childhood vaccines are safe for children with inborn errors of metabolism (IEM), according to results of a retrospective study from a large healthcare system presented here at the Infectious Diseases Society of America (IDSA) 47th Annual Meeting. This study provides reassurance to parents of children with genetic disorders of metabolism that could put them at risk for specific diseases, including autism, researchers announced.

"Children with inborn errors of metabolism are at high risk for vaccine-preventable diseases and death from those diseases. We don't have a strong knowledge base about immunization rates or the safety of vaccines in these children," said Nicola Klein, MD, PhD, from Kaiser Permanente Vaccine Study Center in Oakland, California. "We need evidence-based guidelines for immunization in children with inborn errors of metabolism." She said that this study provides preliminary information on immunization safety.

IEM is an umbrella term for a heterogeneous group of diseases, including hypoglycemia, metabolic acidosis, lactase deficiency, familial hypercholesterolemia, and mitochondrial disorders. Concern has been raised that vaccines might exacerbate an underlying mitochondrial disorder and lead to autism.

This study focused on 79 infants with IEM and 226 healthy matched controls who were members of the Northern California Kaiser Permanente healthcare system from birth to 3 years of age. The study covered the period from 1990 to 2007. Children with IEM were categorized as the sickest (significant risk for morbidity), chronic (slowly progressing), and stable (not expected to deteriorate). Dr. Klein said 7 of the children with IEM had mitochondrial disorders.

At the age of 2 years, no difference was seen in the proportion of children in the IEM group and that in the control group receiving recommended childhood vaccines, including diphtheria, pertussis (whooping cough), and tetanus; polio; measles, mumps, and rubella; hepatitis B; and Haemophilus influenzae type B. No delay was observed for recommended vaccines for children with inborn errors of metabolic disorders.

"Children in both groups were vaccinated at the same rate and at the same time," Dr. Klein told meeting attendees.

Serious vaccine-related adverse events requiring a visit to the emergency department (ED) and hospitalization were analyzed for cases and controls during the at-risk period (day of vaccination and the subsequent 4 weeks) and the postvaccination period (days 31 to 70).

In the overall study population, children younger than 1 year of age at the time of vaccination had 25 ED visits in the at-risk period and 34 ED visits in the postvaccination period; 32 children were hospitalized in the postvaccination period and 44 were hospitalized in the at-risk period. No increased risk for ED visits or hospitalization was seen for children with IEM, compared with control subjects.

For the sickest group of IEM children who were younger than 1 year of age at the time of vaccination, no increased risk for ED visit or hospitalization was observed for either time period.

"This study supports the recommendation that children with IEM receive childhood vaccines. They are safe and can prevent diseases in this at-risk population," Dr. Klein stated.

Although not explicitly stated, this study speaks to parental concerns about the putative link between childhood vaccines and autism, explained Paul G. Auwaerter, MD, MD, IDSA program chair and clinical director of the Division of Infectious Diseases at Johns Hopkins University School of Medicine in Baltimore, Maryland. "This study is reassuring about vaccine safety in this population," he said.

Speaking about the fears that propel the antivaccine movement, Saad B. Omer, MBBS, MPH, PhD, assistant professor at Emory University School of Public Health in Atlanta, Georgia, said that the antivaccine movement has had some unfortunate effects. At his institution, a cluster of people who refused childhood vaccinations was linked to an outbreak of pertussis.

"One child's health should not be dependent on another person's decision [not to vaccinate]. Every child's risk profile depends on who they play with," he said. If a child plays with children who are not immunized against childhood diseases, that child is at increased risk, Dr. Omer pointed out.

Dr. Klein reports financial ties with GlaxoSmithKline. Dr. Auwaerter and Dr. Omer have disclosed no relevant financial relationships.

Infectious Diseases Society of America (IDSA) 47th Annual Meeting: Abstract 187. Presented October 30, 2009.

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