Exploring the genetic landscape of diphtheria, tetanus and pertussis vaccination-associated seizures or subsequent epilepsies

Background Diphtheria, Tetanus, and whole-cell Pertussis (DTwP) vaccination-associated seizures form the commonest type of serious adverse event following immunization in India and are an important reason for vaccine hesitancy. Our study explored the genetic explanation of DTwP vaccination-associated seizures or subsequent epilepsies.Methods Between March 2017 and March 2019, we screened 67 children with DTwP vaccination-associated seizures or subsequent epilepsies, and of those, we studied 54 without prior seizures or neurodevelopmental deficits. Our study design was cross-sectional with a 1-year follow-up having both retrospective and prospective cases. We performed clinical exome sequencing focused on 157 epilepsy-associated genes and multiplex ligation-dependent probe amplification of the SCN1A gene at enrolment. We applied the Vineland Social Maturity Scale for neurodevelopmental assessment at follow-up.Findings Of 54 children enrolled and underwent genetic testing (median age 37.5 months, interquartile range 7.7-67.2; diagnosis at enrolment: epilepsy 29, febrile seizure 21, and febrile seizure-plus 4), we found 33 pathogenic variants of 12 genes. Of 33 variants, 13 (39%) were novel. Most pathogenic variants were found in SCN1A gene (n = 21/33; 64%), SCN8A in 2 children, and 10 children had one variant in CDKL5, DEPDC5, GNAO1, KCNA2, KCNT1, KCNQ2, NPRL3, PCDH19, RHOBTB2, and SLC2A1. Five or more seizures (odds ratio [OR] = 5.3, confidence interval [CI]: 1.6-18.4, p = 0.006), drug-resistant epilepsy (OR = 9.8, 95% CI: 2.6-30.7, p = 0.001) and neurodevelopmental impairment (social quotient < 70) (OR = 5.6, 95% CI: 1.65-17.6, p = 0.006) were significant predictors of genetic diagnosis.Interpretation Our study provides proof-of-concept for genetic aetiology in children with DTwP vaccination-associated seizures or subsequent epilepsies and has important implications for vaccination policies in developing countries.