Immunization Patterns of Children with Chronic Neurological and Neurodevelopmental Disorders: A Cross-Sectional Study from Istanbul

Background/Objectives: Children with chronic neurological and neurodevelopmental disorders (CNDD) constitute a medically vulnerable population in whom routine childhood immunization may be interrupted because of clinical complexity and parental concerns. This study aimed to evaluate immunization patterns, timing of vaccination interruption, and associated clinical and sociodemographic factors in children with CNDDs followed at a tertiary pediatric neurology center. Methods: This prospective cross-sectional study included 545 children aged 1–18 years with chronic neurological and neurodevelopmental disorders evaluated between September and November 2025. Immunization status according to the Turkish National Immunization Program was classified as fully vaccinated, partially vaccinated, or not vaccinated. Information regarding non-NIP vaccines, timing of vaccination interruption, parental characteristics, and motor impairment severity assessed using the Gross Motor Function Classification System (GMFCS) was collected. Associations between vaccination status and clinical variables were evaluated using chi-square tests and logistic regression analysis. Results: Overall, 72.1% of children were fully vaccinated, 25.0% were partially vaccinated, and 2.9% had never received routine childhood vaccines. Immunization status differed significantly across diagnostic groups (p < 0.001). Partial vaccination was more common than complete vaccine refusal across most diagnostic categories. Lower full vaccination rates were observed in autism spectrum disorder and cerebral palsy, whereas higher coverage was observed in Down syndrome. Among partially vaccinated children, interruption of routine immunization after 48 months was the most frequent pattern. In multivariable analysis, only maternal age remained significantly associated with incomplete or no vaccination. Conclusions: Incomplete immunization in children with CNDDs was more commonly characterized by partial vaccination than complete vaccine refusal and followed diagnosis-specific patterns. Evaluating vaccination continuity during pediatric neurology follow-up may help support diagnosis-sensitive immunization counseling.