SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: In our nation-wide ten-year cohort study, we identified SCN1A-related Dravet syndrome as the underlying cause in 1.2% of children reported with seizures following vaccinations in the first two years of life, including 2.5% of seizures reported after vaccination in the first year of life, and 0.3% in the second year of life.