September 17, 2014
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Genetic, structural defects triggered epileptic seizures after vaccination

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Recent data show that genetic or structural defects were the common underlying cause of epilepsy onset after routine vaccination.

Nienke E. Verbeek, MD, MSc, of the University Medical Centre Utrecht in the Netherlands, and colleagues reviewed data from the National Institute for Public Health and Environment in the Netherlands for 990 children who experienced seizures after vaccination during the first 2 years of life. Of these, 26 children were subsequently diagnosed with epilepsy and had seizure onset within 24 hours after inactivated vaccine administration or 5 to 12 days after receiving the measles-mumps-rubella vaccine. Study data was reported from 1997 to 2006.

During the study period, the vaccination schedule included four doses of DTaP, Haemophilus influenzae type B vaccine by age 1 year and one dose of MMR vaccine at age 14 months.

Of the 1,022 possible epileptic seizures among 990 children, 68% occurred after receipt of an inactivated vaccine and 32% after receipt of live-attenuated vaccine in the first 2 years of life. These children had a median age of 11.6 months at first vaccination and 14.2 months at first reported seizure.

Forty-five children were diagnosed with epilepsy. Of these, 26 had vaccination-related seizure onset and 19 had seizure onset before vaccination-related seizure occurred. Children with epilepsy and vaccination-related seizure onset had a median age of 11.5 months at epilepsy diagnosis.

Genetic testing was performed for 14 of 23 children with epilepsy and vaccination-related onset during follow-up. Median age at follow-up was 10.6 years.

Of the 23 children with epilepsy and vaccination-related onset available for follow-up, three had developmental delay before seizure onset and developed mild to severe intellectual disability. Thus, they were considered to have pre-existing encephalopathy. Twelve children were considered to have epileptic encephalopathy. Eight children were diagnosed with Dravet syndrome. One child had epilepsy and mental retardation due to a de novo protocadherin 19 mutation. One child had fever-sensitive epilepsy, which was well controlled after infancy, and another child was diagnosed with West syndrome.

Eight of the 23 children with vaccination-related epilepsy onset were considered to have benign epilepsy. Of these, seven were seizure-free without use of medication at follow-up.

Seizures occurred more often after inactivated vaccines among children pre-existing or epileptic encephalopathy and began at a younger age compared with children with benign epilepsy.

“Underlying genetic or structural causes were identified in 65% of children with epilepsy with vaccination-related onset. These underlying causes were not limited to SCN1A-related Dravet syndrome but extended to other genetically determined fever-sensitive epilepsies,” the researchers wrote. “These results imply that early genetic testing should be considered in children with vaccination-related onset of epilepsy and might help to support public faith in vaccination programs.”

Disclosure: The researchers report no relevant financial disclosures.