Prolonged febrile seizures (that is, seizures triggered by a fever) are a manifestation of Dravet syndrome. Vaccination is a highly effective public health approach that has led to reduced childhood morbidity and mortality from many infectious diseases, and has an excellent safety profile, but in rare cases can be followed by febrile seizures. Given this link, there have been several retrospective studies that have implicated vaccinations in triggering seizures in children with Dravet syndrome, including one which found that 30% of a cohort of such children had their first seizure within 2 days after vaccination.
The current paper describes a prospective study of this link. In four Australian pediatric hospitals, over the course of three years, there were 69 instances of a child under 30 months of age (with no previous history of seizures ) having a febrile (>100.4 degrees) seizure within 14 days of receiving a vaccine. They were grouped with 75 children with febrile seizures not associated with vaccination, and 90 seizure-free controls. A genetic analysis looking for SCN1A mutations was performed on all – only two possessed a known pathogenic mutation for Dravet syndrome, and both were in the group with febrile seizures following vaccination.
These two cases had seizure onset within 24 hours of receiving their four-month vaccinations, comprised of Infanrix Hexa, Prevenar13, and Rotarix. Both had prolonged generalized tonic-clonic seizures lasting 30 and 15 minutes respectively. Both later developed seizure types that were not vaccine-proximate, and both showed developmental delays, and based on electro-clinical studies were diagnosed with Dravet Syndrome. (It was noted that both children have subsequently received further vaccinations under close medical supervision, with anti-fever drugs in addition to their regular antiepileptic medication, and did not experience associated seizures.)
Although the researchers prolonged this study over three years, the numbers were too small to produce statistical significance. Nevertheless, does it imply we should test all children for Dravet syndrome before their first vaccination? The authors don’t suggest this, but do recommend that children exhibiting prolonged febrile seizures after vaccination be tested for SCN1A mutations.