Pediatric Acute Disseminated Encephalomyelitis Triggered by Concurrent Administration of Seasonal and H1N1 Influenza Vaccines: A Case Report and Review of Literature

Background: Acute disseminated encephalomyelitis (ADEM) is a rare, immune-mediated inflammatory disorder of the central nervous system (CNS), typically characterized by the acute onset of multifocal demyelination. The pathogenesis of ADEM remains unclear, but it is believed to be triggered by an autoimmune response, often following viral infections or vaccinations. Case report: This case report describes a 3-year-old child who developed ADEM after receiving two concurrent influenza vaccines: one for seasonal influenza and one for the 2009 H1N1 pandemic. The patient presented with motor regression, mild pleocytosis in cerebrospinal fluid (CSF), and typical MRI findings of ADEM. Steroid pulse therapy resulted in rapid improvement, and the patient recovered fully without sequelae. Results: Although the influenza vaccine has been linked to ADEM in some studies, it remains uncertain whether the simultaneous administration of both vaccines contributed to the onset of ADEM. Conclusions: This case highlights the need for further research into the potential risks of administering multiple influenza vaccines simultaneously, especially in pediatric populations.