title: Prevalence of SCN1A-related dravet syndrome among children reported with seizures following vaccination: a population-based ten-year cohort study.
abstract: OBJECTIVE
  To determine the prevalence of Dravet syndrome, an epileptic encephalopathy caused by SCN1A-mutations, often with seizure onset after vaccination, among infants reported with seizures following vaccination. To determine differences in characteristics of reported seizures after vaccination in children with and without SCN1A-related Dravet syndrome.
  
  
  METHODS
  Data were reviewed of 1,269 children with seizures following immunization in the first two years of life, reported to the safety surveillance system of the Dutch national immunization program between 1 January 1997 and 31 December 2006. Selective, prospective follow-up was performed of children with clinical characteristics compatible with a diagnosis of Dravet syndrome.
  
  
  RESULTS
  In 21.9% (n = 279) of children, a diagnosis of Dravet syndrome could not be excluded based on available clinical data (median age at follow-up 16 months). Additional follow-up data were obtained in 83.9% (n = 234) of these children (median age 8.5 years). 15 (1.2% of 1,269; 95%CI:0.6 to 1.8%) children were diagnosed with SCN1A-related Dravet syndrome. Of all reported seizures following vaccinations in the first year of life, 2.5% (95%CI:1.3 to 3.6%) were due to SCN1A-related Dravet syndrome, as were 5.9% of reported seizures (95%CI:3.1 to 8.7%) after 2(nd) or 3(rd) DTP-IPV-Hib vaccination. Seizures in children with SCN1A-related Dravet syndrome occurred more often with a body temperature below 38.5°C (57.9% vs. 32.6%, p = 0.020) and reoccurred more often after following vaccinations (26.7% vs. 4.0%, p = 0.003), than in children without a diagnosis of SCN1A-related Dravet Syndrome.
  
  
  CONCLUSIONS
  Although Dravet syndrome is a rare genetic epilepsy syndrome, 2.5% of reported seizures following vaccinations in the first year of life in our cohort occurred in children with this disorder. Knowledge on the specific characteristics of vaccination-related seizures in this syndrome might promote early diagnosis and indirectly, public faith in vaccination safety.
authors.affiliation: Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands. n.verbeek@umcutrecht.nl
authors.forename: Nienke E
authors.initials: NE
authors.lastname: Verbeek
authors.forename: Nicoline A T
authors.initials: NA
authors.lastname: van der Maas
authors.forename: Floor E
authors.initials: FE
authors.lastname: Jansen
authors.forename: Marjan J A
authors.initials: MJ
authors.lastname: van Kempen
authors.forename: Dick
authors.initials: D
authors.lastname: Lindhout
authors.forename: Eva H
authors.initials: EH
authors.lastname: Brilstra
mesh_terms: D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004831:Epilepsies, Myoclonic / Q000139:chemically induced / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D008297:Male; D032541:Mass Vaccination / Q000009:adverse effects*; D009154:Mutation; D062550:NAV1.1 Voltage-Gated Sodium Channel / Q000235:genetics*; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D012640:Seizures / Q000139:chemically induced / Q000453:epidemiology / Q000235:genetics*; D014765:Viral Vaccines / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D062550:NAV1.1 Voltage-Gated Sodium Channel; C568242:SCN1A protein, human; D014765:Viral Vaccines