Seizures, encephalopathy, and vaccines: experience in the National Vaccine Injury Compensation Program

To describe the demographic and clinical characteristics of children for whom claims were filed with the National Vaccine Injury Compensation Program (VICP) alleging seizure disorder and/or encephalopathy as a vaccine injury.

The National VICP within the Department of Health and Human Services compensates individuals who develop medical problems associated with a covered immunization. We retrospectively reviewed medical records of children younger than 2 years of age with seizures and/or encephalopathy allegedly caused by an immunization, where a claim was filed in the VICP between 1995 through 2005.

The VICP retrieved 165 claims that had sufficient clinical information for review. Approximately 80% of these alleged an injury associated with whole-cell diphtheria, pertussis (whooping cough), and tetanus or tetanus, diphtheria toxoids, and acellular pertussis vaccine. Pre-existing seizures were found in 13% and abnormal findings on a neurologic examination before the alleged vaccine injury in 10%. A final diagnostic impression of seizure disorder was established in 69%, of whom 17% (28 patients) had myoclonic epilepsy, including possible severe myoclonic epilepsy of infancy. Specific conditions not caused by immunization, such as tuberous sclerosis and cerebral dysgenesis, were identified in 16% of subjects.

A significant number of children with alleged vaccine injury had pre-existing neurologic or neurodevelopmental abnormalities. Among those developing chronic epilepsy, many had clinical features suggesting genetically determined epilepsy. Future studies that include genotyping may allow more specific therapy and prognostication, and enhance public confidence in vaccination.