Impact of SARS-CoV-2 variants and vaccination on pediatric febrile seizures: a retrospective cohort study.

OBJECTIVE: This study aimed to investigate the associations between SARS-CoV-2 variants, inflammatory markers, vaccination history, and demographic characteristics in relation to the occurrence of febrile seizures (FS) in pediatric patients at a single tertiary medical center. METHODS: Retrospective cohort data were collected from a pediatric tertiary care institution between April 2020 and January 2023, encompassing 339 patients with PCR-confirmed SARS-CoV-2 infections. The cohort was separated into FS (n = 102) and control (n = 237) groups. A multivariable logistic regression analysis was employed to evaluate the impact of viral variants (Delta and Omicron sublineages), inflammatory markers (IL-6, D-dimer, CRP), vaccination status (unvaccinated, partially vaccinated, fully vaccinated), and demographic variables, while controlling for potential confounders. RESULTS: The incidence of FS among infants under one year of age was found to be 41.2%, in contrast to 17.7% in older children (OR = 3.2, 95% CI: 1.8–5.7; P < 0.001). Elevated levels of IL-6 exceeding 10 pg/mL and D-dimer levels surpassing 0.5 mg/L were independently associated with an increased risk of recurrent FS (adjusted OR [aOR] = 2.8 and 2.1, respectively), as well as a 3.1-fold increase in the risk of recurrence. Full vaccination was linked to a 68% reduction in FS risk (aOR = 0.32, 95% CI: 0.18–0.55), particularly benefiting infants. Additionally, male infants exhibited a 1.8-fold increased vulnerability (P = 0.016). Omicron sublineages (BA.5/XBB), which accounted for 78.4% of FS cases, correlated with heightened biomarker levels. CONCLUSION: The findings suggest that IL-6 and D-dimer serve as valuable indicators for assessing the risk of FS in children infected with SARS-CoV-2. The association of vaccination with reduced FS risk suggests potential protective effects, highlighting greater susceptibility among male infants. KEY POINTS: • Patients with FS had significantly higher IL-6 (> 10 pg/mL) and D-dimer (> 0.5 mg/L) levels than controls. These elevations were associated with an increased risk of recurrent FS. • Fully vaccinated children had a 68% lower incidence of FS compared to unvaccinated children. • Male infants showed higher FS incidence (41.2%), consistent with established demographic patterns.