Prevalence of <i>SCN1A</i>-Related Dravet Syndrome among Children Reported with Seizures following Vaccination: A Population-Based Ten-Year Cohort Study

<div><p>Objectives</p><p>To determine the prevalence of Dravet syndrome, an epileptic encephalopathy caused by <i>SCN1A-</i>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 <i>SCN1A</i>-related Dravet syndrome.</p><p>Methods</p><p>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.</p><p>Results</p><p>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).</p><p>15 (1.2% of 1,269; 95%CI:0.6 to 1.8%) children were diagnosed with <i>SCN1A</i>-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 <i>SCN1A</i>-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.</p><p>Seizures in children with <i>SCN1A</i>-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 <i>SCN1A</i>-related Dravet Syndrome.</p><p>Conclusions</p><p>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.</p>